open workroom SPONGE LANDSCAPES

Building blocks for an

integrated transformation

sponge

Cahier 2

landscapes

Open Workroom

Hidden Well

loamy top layer with permeable subsoil

based on the Herk and Mombeek catchment

There is a space that defines

the future of food production,

water security and biodiversity.

A space that can help to restore

the global water cycle and

mitigate climate change.

SPONGE LANDSCAPES stand for a

shift in how we manage water and

land. In the face of a changing climate,

we are experiencing the growing impacts

of drought and pluvial flooding. We must

change strategies: From rapidly evacuating

water to retaining every drop where

it falls. From making room for the river

to activating the sponge function across

the entire river basin. And from accepting

the landscape as the sum of sectoral,

often conflicting actions to organizing its

coherent transformation.

SPONGE LANDSCAPES offer a hopeful,

integrating perspective for action. The

86 submissions to the international Call

for Projects & Objects reveal readiness

as well as diverse innovations. We are

getting better at grasping the complex

interactive processes between water and

soils in a diversity of sponge landscapes.

We are forming new territorial coalitions

between nature, agriculture and water

actors. We are looking for shared targets,

timelines and combinations of instruments

and investments.

Yet, SPONGE LANDSCAPES face an

implementation gap. If we continue to

work per sector, target and parcel, it is

certain that we are not going to reach

any of the goals envisioned. Biodiversity

targets will not be achieved within the

confines of today’s protected areas. Without

stable access to fresh water, there

will be no food production. Good water

quality and quantity require interventions

beyond waterways. Are we bound to

keep facing the lack of integration in

space, sectors, policy, capacity and funding?

Or are we ready to make SPONGE

LANDSCAPES a key societal transformation

and organize ourselves accordingly?

We need a watershed moment.

That is why this open workroom is

simultaneously an exhibition, a programme

and a commitment. Let’s share

experiences and channel our efforts to

draw an enabling environment for the

coordinated, timely and appealing transformation

of Europe’s sponge landscapes!

TABLE OF CONTENTS

1 Connecting

sponge loops

2 Designing sponge

landscapes

3 Basin-wide

transformation

4 Sponge

coalitions

5 Re-sponging

Europe

6

16

28

40

52

1

Activating sponge loops

Higher soil

organic matter

increase in

biodiversity

Better soil

structure

FOOD

PRODUCTION

Stimulate plant

growth

BIODIVERSITY

Reducing the heat

island effect

Improved capillary

capacity of the soil

Increase of soil

humidity

Higher river

low flows

Water retention

and tree cover

COOL

ENVIRONMENT

More

infiltration

SPONGE

FUNCTION

Increase of

groundwater

table

WATER

QUALITY

Decrease of

concentration

of nutrients

Reduce

run-off

Desealing

The sponge connects

physical processes

WATER

AVAILABILITY

Increase

drainage base

Upstream

water

retention

WATER

SAFETY

space for

water along

watercourses

Lower river peak

discharge

The sponge function of a landscape refers to its ability

to soak up, store and slowly release water. A regulator

of water, it lies at the heart of a complex system of

interconnected physical processes, binding all actors

and sectors together.

The parameters within these sponge loops are numerous.

We have become champions at monitoring them

separately in every sector, while clearly seeing that

they are intrinsically linked. If we organize ourselves

to positively activate sponge loops (the arrows), we

unlock a chain reaction of benefits in favour of water

availability, quality, safety, food production and biodiversity,

all at once.

Practices from different corners of the sponge web

are trying to quantify the impact of sponge-enhancing

measures – through rigorous scientific modelling,

hands-on field experience, and often a combination of

both. Together, they allow us to envision the scientific

basis and monitoring for the sponge web as a whole. 6–7

1 Stable soil humidity through the age-old

technique of water meadows

Irrigating grassland is an age-old agricultural technique in which water is guided

through meadows via ditches and trenches to stimulate growth and increase hay

harvests. The technique uses only gravity and natural flow and is mainly practised

in winter and spring. It prevents freezing, combats pests, improves soil structure

and adds mineral-rich silt. With the introduction of artificial fertilizers and the use of

modern, heavier agricultural machinery that required drier soils, the technique fell

into disuse in the second half of the twentieth century.

Nevertheless, water meadows can be very valuable in terms of rewetting and raising

the groundwater level. Practical tests in Europe, such as the Lankheet project in the

Netherlands, show that water meadows provide greater stability in soil moisture

compared to meadows that are not irrigated. The water that flows over the meadows

has the time to infiltrate the soil. Because these meadows are not cultivated, their soil

contains richer life and oxygen, which allows them to retain water better. In addition,

these meadows provide room for water: the plots in Het Lankheet can store up to

200,000 m³ of water.

Video still from the

documentary ‘Het Lankheet:

Fascinating Soil Research’

© Water & Land, case Het

Lankheet (2025)

Graph showing soil moisture levels on

different water meadows in Flanders and the

Netherlands, indicating that water meadows

have a more stable soil moisture level than

meadows that are not irrigated.

© Het Lankheet, part of the Sensorisch

Landschap monitoring project (2025)

2025

Active irrigation

@ Pelterheggen

Soil moisture at 10cm

Soil moisture at 40cm

TI = Traditional Irrigation

Research carried out by Water & Land, a project by the Centrum Agrarische Geschiedenis (Centre for Agrarian History)

and the Kenniscentrum Immaterieel Erfgoed Nederland (Dutch Centre for Intangible Heritage), with Het Lankheet in the

Netherlands as one of the case studies.

TI = Traditional Irrigation

2025

Fiche qualité de la structure du sol _ état initial

N° exploitation

N° parcelle

Tout

Tout

2 Better soil structure through a multitude

of adapted agricultural practices

5.5

6.0

6.5

7.0

7.5

10.0

15.0

20.0

25.0

1.0

(CoreVESS au laboratoire)

2.0 3.0

4.0

= porosité grossière de

rayon > 15 µm (=Teneur en air à capacité au champ

( 100hP ))

0.20

A decline in the physical structure of agricultural soils in the north of the Jura led to

the creation of the Terres Vivantes project. In total, 85 farmers were helped to selfdiagnose

and evaluate their soils using practical tests and working with scientific

partners. Based on the site-specific results, these farmers were then invited to

implement a combination of soil-improving measures: among them, maximizing soil

cover, using organic fertilizers, tilling less intensively, and avoiding soil compaction. A

system of points encouraged the farmers to choose the most progressive measures.

They were coached and supported with agricultural and techno-economic expertise,

for example in planning their investments and evaluating the impact of the measures.

6.92

<5.5=très acide | 5.5-6.5=acide | 6.5-7.8=neutre |

très mauvais |

>7.8=basique

= porosité de rayon < 15 µm (Teneur en eau à

capacité au champ (-100hPa ; notée W100))

0.362

mauvais | acceptable | bon

14.5

<12%=très vulnérable | 12-17%=vulnérable |

17-24%=bon | >24%=très bon

= porosité grossière de rayon entre 150 et 15 µm

(notée W10 - W100)

très mauvais |

0.060

0.200


0.0

1.500

3.08

très bonne | bonne | fonctionnelle |

terre fine (notée Da-100)

mauvaise | très mauvaise

1.223

5.0

de la

1.000

potentiel mini | moyen | acceptable | potentiel max

0.00

très mauvais |

43.4%

0.07


(à la capacité au champ)

8.8%

47.8%

Te

rre fine Pores remplis d'air Pores remplis d'eau

A central element of the project was the assessment of the structure and biological

quality of the soils and their evolution across the 185 parcels. Early findings confirmed

a lack of organic matter to ensure a good soil structure in the long term. While it

is still too early to draw general conclusions, results vary widely, as six years is a

short amount of time for soil regeneration. Throughout the project, sociological

and organizational aspects were considered to better understand the motivations

and obstacles involved in adopting soil-improving measures. Most changes are still

a matter of reflection and questioning rather than actually happening in the field.

However, the farmers are eager to engage further environments at the crossroads of

field practice and scientific modelling to put soil-improving measures into practice.

Terres Vivantes is a project of Fondation Rurale Interjurassienne (FRI), Offi ce de l’agriculture et de la nature, Canton de Berne,

Service de l’économie rurale (ECR), Canton du Jura, Switzerland, 2019–27. Among others, the project organised the ‘Soil Your

Undies’ test, in which farmers had to bury underwear in the ground for two months to see how it was affected by bacteria and

fungi. The less of the underwear there remained, the more life there was in the soil.

8–9

Fiche qualité de la structure du sol _ état final

6.0

6.5

7.13

7.0

7.5

<5.5=très acide | 5.5-6.5=acide | 6.5-7.8=neutre |

>7.8=basique

= porosité de rayon < 15 µm (Teneur en eau à

capacité au champ (-100hPa ; notée W100))

8.0

0.000 1.000

0.380

très mauvais |


10.0

15.0

13.9

N° exploitation

Tout

20.0

<12%=très vulnérable | 12-17%=vulnérable |

17-24%=bon | >24%=très bon

= porosité grossière de rayon entre 150 et 15 µm

(notée W10 - W100)

25.0

0.000 1.000

0.051

très mauvais |


0.0

1.500

1.0

N° parcelle

Tout

2.0 3.0

3.38

(CoreVESS au laboratoire)

très bonne | bonne | fonctionnelle |

terre fine (notée Da-100)

mauvaise | très mauvaise

1.200

4.0

1.000

5.0

de la

potentiel mini | moyen | acceptable | potentiel max

= porosité grossière de

rayon > 15 µm (=Teneur en air à capacité au champ

( 100hP ))

0.00 1.00

0.07

très mauvais |

44.5%


(à la capacité au champ)

8.4%

47.1%

Te

rre fine Pores remplis d'air Pores remplis d'eau

Graphs monitoring the initial and final state in terms of soil

acidity; organic matter / clay ratio; soil structure and quality

through visual assessment; air and water flows; water storage

and retention; fine-air water distribution and porosity according

to micro-organism activity; apparent density at field capacity;

distribution of volumes in the soil at field capacity.

© Terres Vivantes

3 Water retention in vegetation

and depaved surfaces

The Flagey and Sainte-Croix squares in Brussels are located relatively upstream in

the densely developed city. Due to the high degree of paving, run-off water increases

flood pressure on downstream areas. The design for the redevelopment provides

significant depaving of both squares by removing 15% of the paved surface and

planting 60 new trees, together with a lush layer of shrubs and perennials. This

improves the vegetation’s ability to capture rainwater, recharges the groundwater

and tempers the microclimate. These interventions help to cool down the square

during the summer months, reduce the heat island effect in the city and create

shaded spaces for various users.

The depaving provides 2000 m² of surface that absorbs, stores and slowly releases

rainwater instead of immediately draining it towards the sewer system. As a result,

50% of rainfall no longer ends up in the sewage network. This significantly reduces

the pressure on the parts of the city further downstream.

The redevelopment of the Flagey and Sainte-Croix squares in Brussels is a project carried out by Fallow, Kollektif

Landscape and Ecorce commissioned by the municipality of Ixelles and Brussels Mobility, 2022–ongoing.

(rain)water reused in the fountain system

(rain)water buffered and infiltrated into green areas

topography of place flagey

non infiltrated or not reused rainwater

Map of the square’s sponge function.

© Fallow and Kollektif Landscape

4 Engineering natural purification

and retention

In Flanders, around 400,000 homes are not connected to the sewage system. The

fragmented landscape with its many ribbon developments makes water treatment

expensive and therefore often unfeasible. In response, HelloWater has developed local,

extensive water-treatment installations that not only purify water but also return it to

the user, such as farmers, or to the landscape to rewet locations where necessary.

One example is the Ledegem becomes L’Eaudegem project. As an alternative to

sewage, a smart combination of settling tanks, pumps, bacteria and plants act as a

local natural waste-water treatment system. Through this project, the municipality

of Ledegem wants to focus on tackling drought, setting up sanitation in rural areas,

and improving surface water quality and biodiversity. From an economic perspective,

this technology is more than 50% cheaper than investing in sewage systems in rural

areas. The water can remain on-site at a good quality, under the supervision of an

intelligent monitoring system.

Alongside implementing these water-treatment installations, HelloWater developed a

digital tool that monitors and steers all projects live according to various parameters,

like the amount of phosphate removed. For the Ledegem becomes L’Eaudegem

project, for example, this has provided a total volume of 19,529 m³ of clean water

since July 2022, as measured on 22 October 2025.

HelloWater is a pioneering water treatment company located in Zwevegem (Flanders). It carries out projects for public

authorities, agricultural businesses and residential clients and developed a data platform for live monitoring of water

treatment systems.

10–11

Within the Ledegem becomes

l’Eaudegem project, a residential

area without a sewage system

is being equipped with a natural

system that purifies waste water

provided by HelloWater as part of the

Water+Land+Schap programme.

© Bob Van Mol

5 Increased drainage base

with drystone check dams

The Greek island of Paros suffers from extreme drought due to the Mediterranean

climate, characterized by high temperatures and limited rainfall during the dry

season, topped by pressure from tourism and the overexploitation of groundwater.

Traditionally, local communities have relied on small-scale water management

techniques to cope with water scarcity. One such technique was the construction of

small dams in seasonal streams that don’t carry water all year round.

These small structures slow down run-off during heavy rainfall, reducing the risk

of flash floods while increasing infiltration and recharging the groundwater table.

Since June 2022, 34 traditional dams have been built along 1.3 kilometres of the

Kavouropotamos, an ephemeral stream on the island. These dams not only tackle

water problems: seasonal ponds form behind the dams, creating valuable habitats for

fauna and flora. The initial results of biodiversity monitoring already show a positive

effect: an increase in vegetation as well as in terrestrial and aquatic invertebrate

populations (for example, more diving beetles and earthworms). To gain a deeper

understanding of the hydrological effects, WWF Greece recently installed water-level

and soil-moisture sensors in the field.

The construction of 34 traditional drystone check dams on the island of Paros in Greece is an initiative of WWF Greece

together with the Mediterranean Institute for Nature and Anthropos (MedINA), the municipality of Paros, the Paros Water

Supply & Sewerage Company and Boulouki. It has been ongoing since June 2022 and is now supported through the

SpongeScapes programme.

These semi-permanent low-height structures

were historically designed to collect small

amounts of water for irrigation.

© WWF Greece

Graph showing preliminary results regarding biodiversity, indicating

that since the construction of the dams in June 2022, there has

been an increase in freshwater (above) and terrestrial invertebrates

(below), such as the Libellulidae (the largest family of dragonflies) and

Collembola (springtails).

© WWF Greece

#

#

MOLSE NETE

DUIVELSKUIL

6 Relating physical (water) processes

to the territory

The water system map and section cover the area around the Duivelskuil

nature reserve between the Molse Nete and Grote Nete. The goal of

the map is to investigate potential measures to prevent the marsh from

drying up and the surrounding agricultural lands from being flooded.

© University of Antwerp

The water system is inextricably linked to the landscape. In fact, the landscape

determines how water flows, both above and below ground, along different streams

in different directions. The water system map shows these potential natural water

flows and indicates where water would naturally infiltrate, accumulate and stagnate

in the landscape. The map aims to enable the evaluation of sponge measures

considering the natural conditions of the landscape. It also gives an indication as to

whether these measures strengthen or weaken the sponge function of the landscape.

The water system maps were developed through smart algorithms that analyse

the topography on different scales in order to identify the interaction of water

flows. At the plot level, the map shows where run-off water collects during heavy

rainfall (blue). At the landscape level, it shows where infiltration measures should

be implemented (brown) and where shallow groundwater appears at the surface in

temporarily wet areas after prolonged wet periods (turquoise).

Research and mapping carried out by the University of Antwerp and the team of Prof. Jan Staes (part of the research

group ECOSPHERE), further included in various projects such as Bodem~Water (Water+Land+Schap) to identify where

certain measures are relevant and also serving as a basis for monitoring certain areas, first versions since 2003.

12–13

Permanently wet

Seepage area

Weeks

Days

Months

Temporary wet

Landscape

depression

Months

Years/Decades

Duivelskuil

Months

Days

Permanently dry

Infiltration area

Ditches

Occasionally wet

Micro-depressions

Months

Months

1:7.500

Years/Decades

Days

Weeks

Molse Nete

Permanently wet

Seepage area

2 Designing sponge landscapes

The Water Battery

sandy top layer with highly permeable subsoil

based on the Kleine Nete catchment area

Tailored strategies for different

sponge landscapes

As we begin to better grasp interacting sponge loops,

we also see how they behave differently depending on

the territory. The landscape greatly influences the speed

and way in which sponges soak up, store and slowly

release water.

In a 100 km radius around Brussels, we have already

identified four types of sponge landscapes in different

(sub)river basins. It is the unique interplay between five

dimensions that sets each landscape apart: deep hydrogeology,

topography, topsoils, land use and even green

water flows.

Across many basins, landscape designers and regional

managers are building a deeper understanding of this

interplay. Drawing these five layers together, we are

beginning to design with and from them, unveiling the

outlines of a new field of design. At the same time, we

are mapping out strategies for basin-wide transformation,

tailor-made to the sponge capacity of landscapes.

16–17

The Water Battery

The Water Battery



The Water Battery

Shallow Lands



Shallow Lands

clayey top layer with impermeable subsoil

based on the IJzer river basin

The Water Battery







Hidden Well


based on the Herk and Mombeek catchment area

Shallow Lands



Mossy Rock

gravel and sandy top layer with impermeable

subsoil based on the Vesdre river basin

Hidden Well

Shallow Lands

Hidden Well







Hidden Well



Mossy Rock

Mossy Rock



Shallow Lands Mossy Rock

Hidden Well





Mossy Rock



Lorem ipsum

Lorem ipsum

Revealing water flows

1 Elbe

‘We create individual agency around water consumption only when we understand

how our actions relate to a greater whole.’ As part of the exhibition Water Pressure:

Designing for the Future, OOZE beautifully interrelated the water flows of the

Museum für Kunst und Gewerbe Hamburg (MK&G) building, the city of Hamburg itself

and the river basin of the Elbe. The map shows the many interdependences across

sectors, scales and activities both upstream and downstream in the river basin.

The research indicates that the Elbe river basin is not defined by single sectors or

boundaries, but by overlapping and interrelated phenomena, made readable in six

layers of reading. A first layer, for example, concerns hunger stones, hydrological

landmarks used historically to indicate low water levels and warn farmers of a poor

harvest. The map and its layers depict a story of exploitation and mismanagement

under the increased pressure of climate change while also recognizing the Elbe as

a territory consisting of interrelated cities, industries and natural cycles that can be

managed.

One of the readings draws our attention to green water flows, water in our

vegetation. Changes in land ecosystems are impacting the hydro-ecological

cycle on a global scale — the process of precipitation, our source of fresh water.

OOZE’s research shows that green water plays a big role in the Elbe river basin,

especially in light of increasing wildfire risks. Forests, for example, not only play a

key role in slowing down run-off and increasing infiltration via their roots, but also

in retaining water in their vegetation and regulating microclimatic conditions via

evapotranspiration.

Design research of the catchment area of the Elbe (Czechia-Germany) by OOZE Architects & Urbanists taken from the

installation ‘Re-Imagine Water Flows: From Building to River Basin’ shown at Water Pressure: Designing for the Future,

an exhibition held at the Museum für Kunst und Gewerbe Hamburg (MK&G), funded by OOZE together with Creative

Industries Fund NL, MK&G in Hamburg, 2024.

Map of the Elbe river basin with six different layers of data. One of the layers draws our

attention to “green water flows”, the water in our vegetation. When terrestrial ecosystems

change, this has a global impact on the hydro-ecological cycle; on the formation of clouds and

precipitation, our main source of fresh water.

© OOZE

Cultivating the productive

sponge landscape

2 Kleine Nete

The Kleine Nete catchment area naturally functions as a big water battery, with

a thick soil layer of sand and gravel that can store large amounts of water. Today,

however, the landscape acts more like a sieve, draining 57% of rainwater to the sea.

LAMA landscape architects described the major drought problems the area is facing

as ‘the heritage of a wet past’, mapping the large-scale drainage the landscape has

undergone in the last 250 years in favour of infrastructure, agriculture and housing.

From the perspective of the natural river, reducing drainage and rewetting the valley

is an obvious choice. Yet this impacts arable lands stretching from the valley to

the plateau. In landscape transformations, farming is too often on the losing side,

because it is managed plot by plot. LAMA explored how the natural sponge function

of the landscape could be restored without losing its productive function in a single

system: a twenty-first-century productive sponge landscape, with the water battery

as the steering principle. 18–19

In the 18th and 19th centuries, the natural sponge function largely determined

land use with large-scale heathland on the plateaus and marshes, swamp forests

and hay meadows in the wet valleys. Farming was located on the flanks, with

fields fertilized with manure from sheep grazing on the heathland, while the hay

from the valley was used solely as winter feed.

© LAMA landscape architects, based on Ferraris 1777

After World War II, artificial fertilizers made it possible to cultivate the sandy

soils of the Kempen on a larger scale. The landscape was drained to make more

land suitable for crops. As a result, the circular agricultural system maintained

through grazing sheep and nutrient recycling was broken.

© LAMA landscape architects, based on agricultural land use 2021

Different landscape structures work together in a circular agricultural system. On the

flanks, where soil moisture conditions are optimal, strip cropping such as potatoes

and legumes follows the contour lines. Between the strips, swales retain run-off and

increase infiltration. At the edge of the lower valley, wider swales purify the nutrientrich

water before it enters the river valley. In this wet zone, reeds or cattails are

cultivated as building material, animal feed or bedding for the stables. The higher sand

ridges act as infiltration zones, where pine forests make space for mixed forests with

open grazed areas. Every farmer manages the area from the lower valley to the higher

sand ridges with dual-purpose cows and sheep grazing from the lower to the higher

areas. Together with the waste streams from vegetable cultivation, hay forms the

winter feed for the livestock.

Design research of the catchment area of the Kleine Nete (Flanders) by LAMA landscape architects with the support of

HOGENT within the framework of De Droge Delta (commissioned by Labo Ruimte, the Flemish Department of Environment

and Team Flemish Government Architect), 2021–22.

A 21st-century productive sponge landscape,

with the water battery as the steering principle.

© LAMA landscape architects

A sponge-driven design strategy

3 Geuldal

Water flows through hollow roads

and dry valleys to the valley

Water is quickly drained away

by narrow, deep streams. The

potential of the valley plain is

minimally utilised

Groundwater is extracted from the soil

through dug stream extensions that

then drain the water

Rainwater is not collected

by vegetation, infiltrates poorly into

the soil and therefore flows down

the slopes

Paved roads flood

during heavy rainfall

Drainage in the soil

extracts groundwater

and carries it away

Poor soil permeability

due to urbanization in

source areas

Water is quickly drained away

by deeply cut streams

to the Geul

Water flows down over the fields

to lower-lying areas

End-of-pipe solutions, often technical, are still the main approach to tackling floods

and droughts. By (re)activating the landscape’s sponge function, we work pro-actively

and from source to mouth. That is the essence of the sponge-driven strategy H+N+S

Landscape Architects developed for the catchment area of the Geul, starting from a

detailed reading of the landscape. The proposal was developed with Bureau Stroming

and Acacai Water, at the request of and in collaboration with a cross-border coalition

of nature organizations under the name Natuurkracht following the floods of 2021.

‘The journey of the raindrop’ goes through six stages

in which this droplet can be slowed down to tackle

both heavy rainfall and prolonged drought.

© H+N+S Landscape Architects

The capacity of the soil

is not fully utilised because little

water infiltrates and groundwater

quickly drains away

Limited sponge effect

on steep slopes, water flows

down to the stream

The flow of raindrops is the steering principle to redraw the landscape: from

interception by vegetation, through soil infiltration and subterranean flow, to

retention and controlled release in surface waters. Measures include slowing down

run-off via vegetation, restoring ditches and creating infiltration strips. Not as

isolated interventions, but as measures for the various stages of the raindrop that

cumulatively work across the entire river basin. Each of them tailored to the local

soil, topography and land use in order to slow down the water. The Dutch side of

the catchment area, for example, features many lime- and sandstone formations as

well as sandy and loess soils, which generally have good sponge capacity, while the

Walloon side of the catchment area is mainly home to ancient rocks and loam layers

deposited in the stream valleys, which have less sponge capacity.

Hydrological modelling revealed a significant positive effect of the various measures

in terms of reducing downstream pressure, as the rainwater is retained longer and

discharged more slowly. The sponge-driven design strategy reveals the impact

of nature-based solutions in tackling water-related challenges and encouraging

governments, landowners, businesses and residents to look beyond technical endof-pipe

solutions. It calls for a design and planning strategy that connects ecological

restoration with agriculture, urban development and cultural heritage.

Design research of the Geuldal (Netherlands-Wallonia) carried out by H+N+S Landscape Architects together with Acacai

Water and Bureau Stroming, commissioned by Natuurkracht, a coalition consisting of WWF, Ark Rewilding Nederland,

Limburgs Landschap en Natuur- en Milieufederatie Nederland, 2022–23.

20–21

Today, the water challenges in the catchment area of the Geul are

reinforced in various ways, for example by poorly permeable soils or

sunken roads that form a highway for water.


In the future scenario, various nature-based measures are incorporated

into the landscape to slow raindrops down and increase the sponge

function of the landscape.


Plateau

with loess, sands and gravel

Water reaches the soil

is retained there and

very slowly finds its way

to the stream

Plateau

with loess, sands and gravel

Steep flank

with sunken roads

Increase sponge effect

on steep flanks by

planting wild grassland

Steep flank

with sunken roads

Slow down runoff water

in sunken roads by roughening

the surface

R A P I D

D R A I N A G E

Valley plain

with stream bed

Slow down surface water drainage

by roughening the valley plain,

design it as a catchment area

Valley plain

with stream bed

Water retention in the soil

by filling in excavated stream

extensions in headwater areas

Collecting rainwater

by expanding the forest along

the edge of the plateau

D E L A Y E D

D R A I N A G E

Water retention in the soil

by removing drainage and extensification

in grassland and arable land

Reinfiltrate runoff water

by diverting it alongside roads

Wide flank

with dry valleys and springs

Increase sponge effect

in cities in source areas through

softening and conscious water use

Slow down surface water drainage

by re-meandering and deepening

mid-stream streams

Wide flank

with dry valleys and springs

Reinfiltrate runoff rainwater

by collecting it in infiltration strips

Plateau

with varying infiltration capacity

Plateau

with varying infiltration capacity

Designing with hydrogeology

4 Leie valley

The phreatic zone of the Leie Valley lies

within a bowl-shaped, impermeable clay

layer, eroded during glacial periods and

later filled with sand.

© CLUSTER landscape & urbanism

Ain’t no river fast enough’ seems to have been the credo of the last 100 years. We

have stripped our landscapes so bare that rivers have been reduced to mere lines.

The sponge landscape requires a deeper and often wider perspective. CLUSTER

applied this perspective when asked to give its advice on the planned rewetting of

the historical meanders along the Leie Canal. The aim was to create space for water

in times of flood risk. The canal, deepened in the 1970s to accommodate shipping,

now lies below the original riverbed. Restoring the meanders would drain rather than

rewet the surrounding lands.

The potential for rewetting and creating space for water lies elsewhere in the valley.

Starting from the hydrogeology, CLUSTER has shown that the Leie valley extends far

beyond the canal and its old meanders, revealing the underlying phreatic groundwater

layer. The underground is traceable to ice-age times, when a bowl-shaped valley of

impermeable clay was eroded – about 20 metres deep and 10 kilometres wide – and

later filled with sand.

The hydrogeology of Flanders determines which areas have greater

sponge capacity than others. This sponge capacity was further

investigated in De Droge Delta.The section shows areas with a deep

phreatic groundwater layer (blue), having more potential to store

water, and areas with a clayey soil, diffi cult to penetrate (white).


Footslope

depression

In the Leie valley, various typologies

can be recognized in the landscape,

with the canal and the old meanders

at the centre, along which we find

infiltration areas on the higher

plateaus. Running parallel to the canal

is the Mandel, which has the potential

to rewet.


Plain of Dentergem

From this closer reading, CLUSTER identified four water systems that connect with

the landscape’s geomorphology, each with its own dynamics and specific potential to

enhance the landscape’s sponge capacity. The Leie Canal with meanders drains the

valley and offers little potential for wetland development. However, the Mandel valley

with sandy levees is ideal for wetland restoration, fed by groundwater from adjacent

sandy ridges. The plains of Tuttegem and Dentergem are sandy areas with dense ditch

networks that can enhance the recharge of groundwater through small weirs. And

finally, footslope depressions at the edges of ‘the bowl’ are ideal to capture, retain

and slowly release run-off water. Designing with hydrogeology reveals how water and

landscape interact, shifting the focus from the canal to the broader riverscape and its

groundwater system.

Mandel

valley

Leie

valley

Plain of Tuttegem

Footslope

depression

Design research of the Leie valley (Flanders) by CLUSTER landscape & urbanism as part of Gebiedscoalitie Droogte

Leievallei (Regional Coalition Leie Valley Drought) and De Droge Delta (The Dry Delta, commissioned by Labo Ruimte, the

Flemish Department of Environment and Team Flemish Government Architect), 2021–22.

22–23

Basin-wide solidarities

5 Vesdre

The risks are often unevenly distributed across the basin. In the Vesdre, for instance,

the flood risks are concentrated in the valley, while the responsibility for managing

these risks lies both downstream and upstream. The multidisciplinary Strategic

Plan of the Vesdre river basin, drawn up by Studio Paola Viganò, the University of

Liège (ULiège) and Yellow Window after the disastrous floods of July 2021 put these

inequalities on the agenda.

The current flood risk conditions stem largely from pre-war industrial urbanization

along the Vesdre and the Hoëgne, along with the development of railways and industry.

The floods disproportionately affected the most socio-economically vulnerable homes

and businesses in the valley, which were already disadvantaged by deindustrialization

and the relocation of activities to the plateaus. On these plateaus, flanks and along

the tributaries, residential development for wealthier families has also increased runoff

pressure, while themselves being less exposed. That is why the Strategic Plan

underlined the importance of intervening on the slopes and plateaus in both rural

and urbanized areas, including the creation of wetlands, green spaces, retention and

storage systems as well as infiltration facilities, adapted to local conditions.

Social vulnerability index by statistical sector

The most vulnerable

Risk and vulnerability :

a spatial The

injustice less

vulnerable

No data, or not relevant

Adaptation to local conditions and landscapes are key: the relationship between

upstream and downstream must always be considered in the specific landscape. At a

broad level, the upstream ‘sponge landscapes’ in the Vesdre can be divided into two.

First, there are the forested and peat-rich areas in the south. Hydrological modelling

reveals that, counterintuitively, restoring spongy peatlands does not significantly

affect run-off reduction, whereas a more mixed forest – rather than monoculture

conifer plantations – combined with adapted management would. Secondly, on the

northern, more cultivated flanks, the restoration of traditional bocage landscapes

with hedges and swales has the potential to reduce run-off by up to 38%. Of course,

all measures contribute to other benefits than the reduction of run-off. The types of

sponge landscapes are diverse and steer the potential solidarities between upstream

and downstream.

Design research of the Vesdre river basin by Studio Paola Viganò based on the ‘Schéma stratégique multidisciplinaire du

bassin versant de la Vesdre’ by Studio Paola Viganò, TEAM-Vesdre ULiège and Yellow Window, 2023. Information about

modelling from ‘Modélisation hydrologique du bassin versant de la Vesdre - Synthèse non-technique’ by Gembloux Agro-

Bio Tech (ULiège), 2024.

The map provides an indication of social vulnerability in the Vesder river

basin. The most vulnerable households are located in the valley, where

the flood risks are also greatest.

-13%

Keyline

design

Restoration of

hedgerows

-38% -11%

© ULiège

Section of the historical riverbed of the Vesder and its tributaries, as

visible on the Ferraris maps (1777), with the areas flooded during the

2021 water bomb marked in red.

© Studio Paola Viganò

-6% à -9%

-1%

Forest

diversification

Peatland

restoration

The impact of the measures

proposed in the Strategic Plan

on reducing surface runoff was

modelled at the river basin level,

with the aim of restoring the

landscape’s sponge function. The

impact during both extreme rainfall

(such as in 2021) and moderate

rainfall was examined.

Sustainable agricultural

practices

-9% à -15% -13% à – 15%

-8% à -13% -5% à – 11%

Appropriate silvicultural

practices

-0% -0% à -1%

© Studio Paola Viganò and ULiège

24–25

3 Basin-wide transformation

Infiltration

Reduce run-off

De-drainage

Buffering

Many small sponge works

make the sponge landscape

Retaining every drop where it falls requires a large-scale

restoration of the sponge capacity. However, rather than

grand infrastructure projects, it is the accumulation of

many modest, local sponges that builds up a resilient and

productive landscape.

The list of potential sponge measures is long, but their

impact depends on their location in the landscape. What

works well on upstream loamy hillsides differs from

what’s needed in downstream grasslands. A well-intended

infiltration measure may even lead to extra drainage.

While the transformation of every village square,

forest and field can contribute, they need to unfold at the

right place, at the right time, in the right way.

This collection of photographs showcases a diversity of

sponge projects that have been realized or are currently

being implemented. They are gathered and ordered

as if in a fictional basin, trickling down from sources

to mouth. As ‘Retain the water drop where it falls’ is

the motto, all projects together add up to a basin-wide

transformation!

28–29

1 Contour farming

WasserKultur developed a water management system

based on the ‘Slow, Spread, Soak and Store’ principle

and the KeyLine method, where contour lines shape

the agricultural design. A system of ditches and swales

increases infiltration and slows down run-off, supported

by basins and ponds that store rainwater. Low-growing

shrubs and other agroforestry measures between crops

improve soil structure.

‘NaturGut Katzhof’, WasserKultur (Switzerland), 2021–ongoing.

© NaturGut Katzhof (before) and Thomas Alföldi (after)

3 Infiltration graveyard

The heavily paved cemetery in Menen was transformed

into an infiltration graveyard. Permeable surfaces, wellpositioned

wadis and new plants encourage a more dynamic

and uncontrolled model of green spaces management while

collecting and buffering run-off water.

‘Parkbegraafplaats’, Fallow and Plant & Houtgoed for the city of Menen (Flanders),

2023–24. © Lars Duchateau

2 Pitted fields

4 Swales on ridges

In Voeren, 765 metres of swales were dug along the contour

lines of grassland and farmland slopes. Combined

with newly planted trees, bushes and hedges, they

reduce run-off all the while mitigating erosion and restoring

robuster and more biodiverse landscapes. Swales are

a modern version of graften, terraces overgrown with

vegetation traditional of bocages.

Regional Landscape Haspengouw & Voeren and Landscape park Grenzeloos

Bocageland , 2024–ongoing. © RLHV

Small ditches between the rows of corn, dug by a

specially designed machine, allow the rainwater

to infiltrate more effectively. Fourteen field trials

on Belgian loamy soils showed that this micropitting

technique reduced soil and water loss by

83% and 69%, respectively.

Centre indépendant de promotion fourragère (Belgium) © CIPF

5 Nibbled streams

To slow the flow and reconnect the Grondelingbeek

stream with its surrounding landscape, this tributary

of the Herk river was reshaped through the raising of

its bed and the addition of green buffers. The stream

was re-meandered by the ‘nibble method’, a simple

technique where a chunk of soil is moved from one

bank to the other to create minimal bends and flow

changes in the stream bed.

7 Seasonal weirs

In the catchment area of the Aa river, thirteen adjustable

weirs have been installed and repaired, allowing water to

be retained in the watercourse for longer and enabling

farmers to seasonally manage the groundwater level on

their parcels, while replenishing the groundwater table.

{beek.boer.bodem} , local farmers with the support of Boerennatuur Flanders and

the Province of Antwerp (Flanders), since 2019. © Bob Van Mol

Grondelingebeek, Province of Limburg and Regional Landscape

Haspengouw & Voeren together with Natuurpunt, Watering de Herk and

the municpality of Heers (Flanders), 2017–24. © Province of Limburg

6 Drought-resistant crops

In the Gete catchment area, seven farmers are experimenting

with hemp cultivation to explore its potential for climate adaptation

in agriculture. Hemp is a drought-resistant crop that has a

positive impact on soil structure and can store a lot of CO2.

‘Water als bondgenoot in de Getestreek’ , Regional Landscape Zuid-Hageland and the

Province of Flemish Brabant (Flanders), since 2019. © Bob Van Mol

8 Soaked forest

In the Italian region of Veneto, 2.5 hectares of cornfields

were transformed into a permanent lowland

forest amid the intensely cultivated Po valley. As part

of this transformation, the Bosco Limite forest has an

intricate hydraulic system, made of canals and wells,

infiltrating more than 1 million m3 of water per year.

‘Bosco Limite’, Etifor together with the private landowner, 2011–13.

© Etifor

9 Where waters

(used to) flow

The Moermanpark redevelopment reconnects the city

with its river basin, transforming the former parking lot

into a sponge square. Following the shape of the Sint-

Amandsbeek stream, its permeable surfaces and open

basins are designed to accommodate rainfall with a

100-year return period. The flexible sewage and planting

strategy slows, stores and filters rainwater.

‘Moermanpark’, OMGEVING together with VK architects+engineers in

the city of Roeselare (Flanders), 2022–24. © city of Roeselare

11 Marshy trails

The depaving and rewetting of the 1-km-long canal

along the Preshoekstraat slows down drainage and

increases infiltration. A pedestrian trail along a mosaic

of biotopes is created, from wet and marshy zones to

forest habitats, ideal for certain plants such as watercress

to thrive.

‘Van Beek tot Bodem’, the city of Kortrijk and the Agency for Nature and

Forests (Flanders), 2023–25. © city of Kortrijk

12 Recycled sources

10 Sponge yard

The Ilot d’Eau Ensemble project explores how residential

gardens, often overlooked in the water cycle,

can act as urban sponges. Through co-design workshops,

residents, designers and municipal actors

transform lawns, gutters and driveways into networks

of basins, ditches and ponds. The project shows how

small DIY actions can transform each garden into a

micro-landscape that buffers stormwater and nurtures

biodiversity.

‘Ilot d’Eau Ensemble’, LATITUDE Platform for Urban Research and Design

(Brussels), 2022. © LATITUDE Platform (before) and Bruno Dias Ventura /

LATITUDE Platform (after)

A new water source of 16,500 m3 in Ledegem

addresses the increasing risk of drought and pollution

caused by the discharge of untreated water and proposes

a decentralized water strategy for rural areas. A

nature-based system with advanced nutrient-removal

processes and smart water-quality sensors instead of

chemicals or grey infrastructure captures rainwater

and locally treated wastewater, providing a reliable

source of clean water.

‘Ledegemse Meersen’, the municipality of Ledegem, Province of West

Flanders, HelloWater, Persyn NV, Studiebureau Demey and Resourcefull,

2025. ©HelloWater

13 The beaver effect

Beavers are the ultimate experts in low-tech sponge measures,

capable of building resilience across the catchment

area. Farmers and river syndicate members along tributaries

of the Lèze river constructed six beaver dam analogues using

branches, piles and other natural materials to slow the water

flow and create naturally spongy biotopes.

SpongeWorks, SMIVAL (Syndicat Mixte Interdépartemental de la Vallée de la Lèze) and

MAPCa (Mouvement d’Alliance avec le Peuple Castor), 2025. © SMIVAL

14 Buffer square

The main square of Sint-Niklaas was transformed into a climate

regulator for the city. To preserve the underground parking,

rainwater is being diverted to a sunken garden, an underground

buffer system, lined above the surface with trees. Ponds, pools

and fountains are introduced to cool the temperature, while

lawns help to slow down evaporation and enhance infiltration.

‘Main square Sint-Niklaas’, LAMA landscape architects, SWECO and Artgineering for

the City of Sint-Niklaas (Flanders), ongoing. © LAMA landscape architects

15 Rewetting a drained

landscape

Steenbossen, a historic bocage landscape drained for

agricultural purposes over the years, was rewetted to

reduce the risk of flooding and create new nature and

recreation areas. The new wetland ecosystem was

designed to restore and re-meander the watercourse.

It includes large-scale reforestation with the introduction

of species adapted to the wet soil conditions in

the winter bed.

‘Steenbossen’, Atelier Horizon and Antea Group for the municipality

Puurs-Sint-Amands (Flanders), 2022–25. © Atelier Horizon (before) and

Antea Group (after)

16 Landscaping dykes

Instead of monotonously reinforcing existing artificial

dykes, the redevelopment of Ooijen-Wanssum introduced

a series of natural ones, avoiding deep sand

extraction and giving more space to flood resilience,

agriculture and nature. The dykes act as living landscape

elements over more than twenty kilometres,

creating more than 500 hectares of natural areas and

improving connections between the villages and the

river.

‘Maaspark Ooijen-Wanssum’, H+N+S, Ploegam, Fugro, Arcadis, Dura

Vermeer and Trafique B.V. (Netherlands), 2018–21. © Paul Poels (construction)

and Hans van den Meer (after)

4 Sponge coalitions

Infiltration

Reduce run-off

De-drainage

Buffering

No basin-wide implementation

without a watershed

If many sponge works make the sponge landscape, a

multitude of actors are at play. Indeed, sponge measures

land where people live, cows graze, forests thrive and

businesses operate. The public sector relies on getting

private land users on board, and the private land users

point to the public sector to get the ball rolling.

Who takes the lead when responsibility lies with many,

but at the same time no one? Transformation does not

happen by itself. Whether driven by urgency or potential

win-wins, we see many coalitions emerge that unite

agriculture and nature organizations, local initiatives,

municipalities, policymakers, landscape managers and

water managers behind shared sponge ambitions!

Coalitions arise and operate very differently depending

on the context. Still, we can identify recurring strategies.

Inspired by the work of existing territorial coalitions, five

essential conditions for mobilization across the entire

basin are assembled. 40–41

2050

1 From interdependences to

shared ownership

The various actors in the sponge landscape each operate

according to their own needs and priorities, and that is

indeed their prerogative. However, they are interconnected

within the landscape, now reinforcing each other, now

causing friction. Building a strong coalition starts with

recognizing these interdependences and building onto them

a sense of shared ownership and agency over their collective

future.

Publication: The landscape biography of the Flemish Ardennes reveals

both its complexity and its shared values. It tells the story of how landscape

transformation is of all times. Three landscape types define the vision – source

landscapes, bocage landscapes, and villages – deliberately steered towards

interdependences rather than on a single sector.

LANDSCHAPSBIOGRAFIE

VLAAMSE ARDENNEN

Landscape biography of the Flemish Ardennes.

© Commissioned by the province of East Flanders

and Regionaal Landschap Vlaamse Ardennen,

research by OMGEVING, 2023.

Pano documentary “Slag in het water” (Battle in the water)

© VRT, 2024

Water flow in the Spalbeek (Herk)

2012 2017

Video still: Never waste a good crisis. Crises bring the interdependences to the

forefront – in the case of the Dender, between public amenities and water. While

the threat of polarization is high, it is also an opportunity to build on a common

story, basin-wide.

Ecological minimum flow rate

Unacceptable damage

Figure center: In the Herk and Mombeek streams, farming as well as nature

organizations and water managers collectively identified 2017 as a damage

boundary: the landscape was to be made resilient so that any new damage would

not be worse than before 2017. As can be seen from the graph showing the low

water flow in watercourses over time, 2017 stands out as an important tipping

point regarding the ability to recover from dry periods. This formed the basis

for the modellers to calculate basin-wide sponge targets in terms of infiltration,

buffering and drainage reduction.

More infiltration on

15.000 ha (= 1/2 of area)

Reduce rapid drainage on

7.200 ha (=1/4 of area)

How can we reduce

future risks to the

situation pre-2017?

More buffer space for

1.500.000 m 3 additional

buffering (T20)

Reducing water demand

through changes in

cultivation, nature

restoration, constructing

irrigation reservoirs, etc.

Graph showing the low water flow (Spalbeek, Herk) and sponge targets.

© KU Leuven and Architecture Workroom Brussels for the Living Lab Herk & Mombeek

Process scheme of the Living Lab Herk & Mombeek.

2 Working together within

a co-creation process

A shared, open, dynamic and step-by-step process starts from

shared ownership to set a clear collective direction. Sponge

landscapes may not be implemented overnight. This does not

mean that first steps cannot aim for a bigger whole, whether

they are demonstration projects or strategic planning for the

long run. The balance between short-term milestones and longterm

horizon keeps everyone on board.

Figure below: The role and degree of involvement of coalition members evolves

through time. The Living Lab Herk & Mombeek process was structured in five phases

of co-creation. In the target-setting phase, larger work sessions gathered many

stakeholders to discuss the damage experienced. In the formulation of the action plan,

numerous bilateral discussions were more relevant to sharpen how each stakeholder

could contribute to translating the targets into actions.

42–43

© Architecture Workroom Brussels

INTERDEPENDENCES

1 CHALLENGES COALITION

DAMAGE BOUNDARY

2 COALITION

TARGETS

RESILIENCE

3 TARGETS

WHAT

A

IS FEASIBLE?

4

SCENARIOS

PRIORITIES

SCENARIOS ACTION PLAN

INVESTMENTS

5 ACTION PLAN IMPLEMENTATION

Video still: The action plan of the Living Lab Herk & Mombeek formulates first

measures with the one-million-euro implementation funds provided by the

investment programme ‘Weerbaar Water+Land+Schap’ programme (Resilient

Water+Land+Scape). However, the plan sets the direction for a long-term

implementation, calculating that nearly 50 million euros of funding will be needed to

achieve the objectives set for 2050. The funding available today goes first to field labs

that aim to set the cumulative impact of sponge measures in motion.

Implementation project on plots

owned by the municipality

Figure above: By engaging locally, a larger cascade of projects is activated. Within

T.OP Dender, projects are initiated on various scales within a broader framework,

from Extra Large (the entire basin) to Small (local initiatives). For example, the

Dorpsbos in Roosdaal plays an important role in the green blue network that is

envisioned for the entire Dender basin. Roosdaal is situated in a strategic location

because of its couters and plateaus, which are suitable for infiltration. The Dorpsbos

initiative is seen as a pilot project within the basin for upscaling several smaller scale

local actions which are intertwined with each other.

Video ‘Weerbaar Waterlandschap:

Living Lab Herk & Mombeek’.

© Storyrunner together with

Architecture Workroom Brussels,

2025

2

5

3

1

Vision on the scale of the inner

zone

Narrative across projects:

softening of Kappelleweide (1),

Gasthuisstraat (2), Zonnelied

care homes (3), Sponge forest

(4), Transition test centre (5)

4

3 Multi-stakeholder on all levels

To activate positive interdependences in the sponge web,

we need many actors and sectors on board. Knowledge,

responsibilities and policies are traditionally organized by

sector. They need to be brought together and jointly developed

for sponge landscapes to be implemented. Thorough

collaboration allows for shared insight to become shared

action, even for the most complex challenges.

Dorpsbos as part of the

green-blue structure of the

Dender river basin

Scheme and scale model of the Dorpsbos within the broader framework of T.OP Dender.

© MAAT ontwerpers

Figure bottom right: The coalition includes a broad network of farmers, local

agricultural research centres (e.g. PC Fruit) and interest groups (e.g. Boerenbond)

as well as the provincial and regional agricultural departments. All cooperate closely

with counterparts from other sectors at every level. Everyone can play their own role,

activated at different moments in the process.

SCIENCE

by hydrological and

agricultural modelling

Figure bottom left: Within the Territorial Development Programme elaborated for

the Dender valley (T.OP Dender), the different, often more sectoral measures are

clustered into a place- and project-based logic. They are the result of intensive years

of co-creation and analysis, and guide the intergovernmental integration of resources

in a long-term investment programme.

TOEKOMSTGERICHTE LOCATIES BESCHERMEN

A. Centrum beschermen met verhoogde kade

B. Aaneengesloten hoger gelegen bebouwing beschermen met dijk

C. Waterrobuuste herontwikkeling van activiteiten

D. Maatregelen voor individuele gebouwen / sites

OVERSTROMINGSRUIMTE BESTENDIGEN

E. Onbebouwde ruimte vrij houden

SLEUTELPROJECTEN

3 STEDELIJKE DOORTOCHTEN

4 DWARSE LINTEN

VALLEIBREDE PROJECTEN

ECO-HYDROLOGISCHE HERINRICHTING MEERSEN

LAND USERS

agriculture, nature,

urbanisation, water

management,

recreation, etc...

F. Veilig overstroombare tuinen

VEILIG OVERSTROOMBARE TUINEN

DE VALLEI HERSTELLEN

G. Ruimte voor water maken

H. Overstromingsdynamiek vanuit de Dender bevorderen

I. Het watersysteem optimaliseren

TRAJECTBEGELEIDING INDIVIDUELE BESCHERMING

PROACTIEF AANKOOPBELEID

VERGUNNINGENPLATFORM EN GEBIEDSGERICHTE

HANDHAVING

SPATIAL

INTEGRATION

by design research

and process facilitation

POLICY

as a matchmaker of

instruments, targets

and capacity

J. Brugopeningen verruimen als opportuniteit

K. Activiteiten herlocaliseren bij grote wijzigingen

PROJECTEN UIT OPPORTUNITEITEN

Financing scheme.

© T.OP Dender

PARALLELLE PROJECTEN

44–45

Organization chart of the Living Lab Herk & Mombeek.


Bufferen

47.255 m 3

In bufferbekkens van 1m hoog

47.255 m 2

= 12 bufferbekkens

Infiltreren

31.609 m 3

In infiltratiebekkens van 0,2 m hoog

158.045 m 2

= 50 infiltratiebekkens

Irrigeren (Landbouw)

59.945,59 m 3

In irrigatiebekkens van 1 m hoog

MET 40% verlies door verdamping

83.923,83 m 2

= 25 irrigatiebekkens

Irrigeren (Natuur)

6500,00 m 3

In irrigatiebekkens van 1 m hoog

6500,00 m 2

= 2 irrigatiebekkens

Stuwen waterloop

10,5 km waterloop

Impact 50m aan beide oevers

Oppervlak:

97,5 ha impact

= 36 stuwen

Buffer

en

47.255 m 3

met overstromingshoogte van 0,1

m

472.550 m 2

3 31.609 m x 0,20 = 158.045 m

2

158.045 m / 6 m =

26,3 km

De-draineren

Akkerpercelen (35%) op natte gronden

(d-e-f-h) omvormen tot grasland

5,3 ha akker

omgevormd naar grasland

4,1 km

waterloop aangepakt

Vochtvraag reduceren

4 Field expertise x modelling x design

Complex challenges require innovative and tailored solutions

that no single actor is equipped to develop alone. Bringing

together different areas of expertise without hierarchy

generates intensive interaction and collective knowledge

development. The modelling of measures provides scope

and potential. Design-based research makes the scale of the

transformation tangible. Local knowledge matches these

insights with reality.

Extreme scenarios for an upstream region

(Piringen).

© CLUSTER landschap & stedenbouw,

for the Living Lab Herk & Mombeek

Maps above: The water security goals calculated by the modellers in the Living Lab

Herk & Mombeek were translated into the upstream case of Piringen using two

extreme scenarios. A purely civil engineering approach (left) results in numerous

concrete basins. This would be very expensive to build and maintain and would

require an advanced system of pumps and pipes. A water systemic approach (right)

ensures a freely floodable valley, something which can be considered in relatively

unbuilt Piringen but is less acceptable in valuable peat areas or where the valley

is narrowly built up. The scenarios help to move beyond self-interest and abstract

principles and make the scale of the required transformation tangible.

... 2023 June 2024 August 2024

September 2024 November 2024 Winter 2024-2025 March 2025 April 2025

75%

Looking for 64.000 m 3

of infiltration pools

Hydrological modelers assess

the impact of extreme weathers

on the landscape and crop

loss. 64.000 m 3 of infiltration

measures need to be taken to

be resilient. They translate this

to an infiltration pool of 75 m 3

per 10.000 m 2 in 75% of the

landscape.

Which compensation

for the loss of land?

Conversations with farmers

soon reveal resistance, as the

advantages do not outweigh

the loss of land. There are also

doubts within the local coalition

about the effectiveness and

implementation of infiltration

ponds, especially in loamy

soils.

Increase carbon content is

priority number 1

The local coalition proposes

measures that increase the

carbon content in the soil and

roughen the arable lands.

These measures offer visible

win-wins for agricultural

practices.

A learning network helps

tackle obstacles

Farmers are interested in

increasing their carbon

content, but still encounter

many obstacles, such as “How

can I get enough organic

material?” and “How long will it

take before I see an increase

in return?”. The idea of setting

up a Soil Learning Network is

born.

Let’s get key players

involved

Although farmers are very

willing to participate, they are

not always in control. For

example, they are dependent

on calendar deadlines. The

learning network is expanding

into a broader network with

crop confederations, contractors,

and other key players.

It’s not enough, boundary

measures are necessary

New model calculations show

that these measures are not

sufficient to achieve the

infiltration goals. Additional

infiltration volume is needed, as

well as measures that increase

the drainage base and reduce

run-off. The decision is made to

focus more on boundary

measures.

A new source for

wood chips

Farmers report a lack of

organic material in the area.

The idea arises to install

wooded edges, manage them

locally, and use them as a

source of wood chips. This

leads to the creation of the

sponge measure ‘Wooded

edges with micro-depressions

and wood chip management’.

Ready, set, go!

The goal is set and the coalition

agrees on the necessary

measures. Carbon content

needs to be increased everywhere

possible and we need

more than 10 km of wood edges

with micro-depressions.

What about existing

instruments?

Agricultural policy provides

instruments to install wood

edges. However, the lack of

prefinancing and insufficient

coverage form obstacles for

farmers. It is uncertain if the

combined sponge measure of

wood edges + micro-depressions

+ wood chip management

falls in this definition.

10.000 m 2

CO

75 m 3 2

CO 2

CO 2

But how will we realise

?

this? The search for

appropriate instruments

=

begins!

=

Maybe with erosion

instruments?

Although the wood-edges are an

effective measure against

erosion, the erosion decree will

not support their realisation. The

presence of sediment in run-off

water must be proven with

photographs. Even with photographs,

a measure that

combines infiltration with

erosion, is less likely to be given

finances.

We found our partner!

The Regional Landscape

Zuid-Hageland has built up

considerable expertise in

planting wood edges in recent

years. They see potential in the

combination with micro-depressions,

but will need flexibility to

figure out the best way for

execution.

?

Facing a dilemma

Although there is interest in more

organic material in the area,

almost no farmers seem

convinced by the permanent

character of wooded edges. We

are looking for solutions to this

resistance through temporary

instruments. The dilemma: no

wooded edges, or wooded edges

that may disappear after five

years.

Where are the sponge

tools?

The instruments to realise

sponge measures do not exist

today. A collective effort is

needed to rethink frameworks,

rewarding systems and instruments

that make their realization

possible.

Timeline showing the development of ‘wooded

edges with microdepressions’ as measures in the

Wissenbos catchment area.

© Provincie Vlaams Brabant

Timeline: The timeline maps the interaction between modellers, design researchers

and local farmers in the Wissenbos catchment area. It highlights both the importance

of an open process of interaction – balancing between feasibility in the business

operations of farmers and the calculated water goals – and the need for spaces

of experimentation in the creation of measures such as wooded edges and

microdepressions.

Map below: In the city of Menen, a building promotor planned to redevelop a former

industrial site to meet housing demands, while the city identified the same site as

crucial to uncover the Geluwe stream. After attempts to reconcile the two objectives, a

hydrological study proved to be a game changer. It mapped out the required buffer and

infiltration volumes for the entire catchment area, identifying the site as one with high

buffer potential, providing the city with a strong argument at the negotiating table.

46–47

Map of the necessary buffer volumes along the Geluwebeek stream.

© Architecture Workroom Brussels, based on the Hydroscan study,

as part of the Project Subsidy Green-Blue Veining.

5 Matching individual entrepreneurship

with the watershed movement

Real stakes enable real change. Why would you join if you

feel you can’t change anything? Change comes within reach

when it is matched with present dynamics, worries and

entrepreneurship. The role of the sponge coalition is to build

trust and organize the entry points for local actors to engage

with the movement, voluntarily yet with commitment.

Figure above: A sponge landscape is the sum of many initiatives. Within the

framework of Territorial Development Programme elaborated for the Dender valley,

various supralocal work programmes are being developed on a large scale. Smaller

projects tie in with these and become part of a larger whole. This multiscale model

offers various entry points: a project can be included and supported within T.OP

Dender if it fits within one of the ongoing work programmes. The plan also includes a

wide range of actors in different ways. Local organizations are mainly involved in local

pilot projects, while government agencies, such as the Flemish Environment Agency

(VMM) and the Agency for Nature and Forests (ANB), are mainly active at the level of

the larger programmes.

Figure below: Sponge measures should be implemented by various land users,

both downstream and upstream. This also applies to farmers, who play a key role

in improving the sponge capacity of their plots. During sessions in the various

local coalitions within the ‘Weerbaar Water+Land+Schap’ programme (Resilient

Water+Land+Scape), it became clear that this must be tailored to the specific

business operations, and that respecting entrepreneurial freedom is crucial. A

step-by-step strategy was developed, based on quick wins and no-regret measures

that also yield short-term benefits for farmers in their current business operations,

without closing the door to more structural or radical measures where necessary.

Fiches: The Living Lab Herk & Mombeek focuses on the win-wins of sponge measures

within a basin-wide strategy. It supports and activates individual land users with

targets for the whole basin on the horizon: farmers can roll out measures that fit

within their business operations, municipalities can tackle other challenges such as a

lack of high-quality green-blue space, and nature organizations can integrate it with

nature values.

Organization chart of T.OP Dender.

© Departement Omgeving

Step-by-step approach within the agricultural sector.


(Weerbaar Water+Land+Schap)

SHORT TERM (0-2y)

Meersen

recovery

1° SOIL & CULTIVATION TECHNIQUES

On the short-term, significant gains can be

achieved with adapted soil and cultivation

techniques such as non-inversion tillage or

carbon build-up, which enhance the soil’s

sponge function.

© Bob van Mol

2° CLOSING AGRICULTURAL CYCLES

Closing agricultural cycles offers

opportunities. Grasslands for example are

disappearing because they today have little

added value for agricultural activities, partly

due to the decline of livestock as a result of

the nitrogen crisis. However, grasslands

could be re-exploited to close cycles within

farm operations.

© Provincie Limburg

3° EDGE-OF-FIELD MEASURES

Hedgerows and grass buffer strips make an

important contribution to the water system

and create win-wins: improving biodiversity,

they also reduce sediment run-off.

W1/ Room for water

Dender Valley

Regional programme

Urban

passages

Programme plan T.OP Dender

AANPLANTEN KLE’S

W2/ Green-blue W3/ Strategic

Denderflanks

leverage sites

Regional programme

AP Node NI AP AP AP

Molenbeek-

Vondelbeek

Zandbergen

Coalition T.OP Dender

+

Afstroming

vertragen

Infiltratiecapaciteit

vergroten

Drainagebasis

verhogen

Buffercapaciteit

vergroten

+++ + +

SP

Denderknoop

P P P P P

P P P P P

P P P P

A range of sponge measures.

© CLUSTER landscape & urbanism, with the support of Architecture

Workroom Brussels (Weerbaar Water+Land+Schap)

MAXIMALE BODEMBEDEKKING

+

Afstroming

vertragen

Infiltratiecapaciteit

vergroten

Drainagebasis

verhogen

Buffercapaciteit

vergroten

+++ + ++

supra-local

sites

bundled projects

and action plans

local pilot

projects

© Bob van Mol

Grasland - Akkerland - Fruitland

4° CROP PLAN DESIGN

The design of agricultural plots can be

revised when they are replanted every x

number of years, for example by aligning

the direction of machinery with the contour

lines.

Met de aanplanting van kleine landschapselementen wordt het landschap verruwd (ontstaan van een

microreliëf) waardoor water vertraagd wordt afgevoerd en waar het lokaal blijft hangen kan infiltreren.

ALTERNATIEVE TEELTEN

Niet elke KLE heeft hetzelfde effect naar waterinfiltratie, buffering of water vertragen en de koppelkansen

zullen dus verschillend zijn naargelang de gekozen KLE.

KNELPUNTEN

+ Nood aan een redelijk vergoedingssysteem voor landbouwers

+ Permanente ingreep op lange termijn

+ Beheer en onderhoud van KLE’s

+ Beschikbaarheid van ruimte (vb. in intensief gebruikte landbouwgebieden)

Akkerland - Fruitland

Buffercapaciteit

vergroten

+

Afstroming Drainagebasicapaciteit

Infiltratie-

vertragen

verhogen vergroten

+ + +

5° ALTERNATIVE CROPS

6° LAND EXCHANGE

© PC Fruit

© Bob van Mol

The water demands of crops will increase

significantly in the future. Many farmers are

already innovating with drought-resistant

crops. It is important to map these

developments and disseminate knowledge.

In the future, some land uses will not be in

balance with the available water supply. On

a larger scale, this calls for solutions such as

land exchange or well-considered land use

planning.

RUIMTELIJKE RANDVOORWAARDEN

Maximale bodembedekking vertraagt het afstromen van regenwater, waardoor het meer tijd krijgt om in

+ Rekening houden met

de bodem

de openheid

te infiltreren,

van het

geholpen

landschap

door

bv. weidevogelgebied

het wortelstelsel. Bij het zaaien van gras moet opgemerkt worden

+ De locatiekeuze moet afgestemd

dat dit eigenlijk

worden

ondieper

op de waterdoorlaatbaarheid

moet gebeuren dan bij graan.

van de

Als

bodem

beide

en

gewassen

de mogelijkheid

om water vast

tegelijk worden gezaaid,

kan

te

dit

houden

soms leiden tot een minder dichte grasmat. Het is daarom aan te raden om te kiezen voor een

+ Landschappelijke inpassing

traaggroeiend en laagblijvend ondergewas, zoals gras, klaver of een mengeling daarvan. Dit ondergewas

moet na een aantal jaren, meestal na 4 tot 6 jaar, opnieuw worden aangelegd.

KNELPUNTEN

KOPPELKANSEN VARIANTEN FINANCIEEL

+ Concurrentie met de hoofdteelt om water en voedingsstoffen

+ Biodiversiteit

+ Hagen

+ Nood aan extra beheersmaatregelen

+ Kwaliteit van het landschap

+ Houtkanten

€ € €

+ Risico op plaagvorming

+ Erosiebestrijding en natuurlijke plaagbestrijding

+ Solitaire gezaaid bomen worden dan het graan. Dat levert bij tegelijk zaaien wel eens

+ Knotbomen

+ Gras moet eigenlijk ondieper * Er zijn meerdere instanties

waar subsidies kunnen worden

verkregen Akkerland voor aanleg

een dunnere stand van het gras op

+ Beeldkwaliteit

of onderhoud van kleine

+ Beheersresten kunnen RUIMTELIJKE worden omgezet RANDVOORWAARDEN

landschapselementen

naar compost

Alternatieve teelten kunnen ervoor zorgen dat enerzijds de watervraag daalt of er gewassen worden

+ Er is nood aan een aangeplant bodem met die een vroeger goede op structuur het jaar, met wanneer een goede er nog ontwatering meer beschikbaar is, hun kritisch groeimoment

kennen. afgestemd Daarnaast worden kunnen op het teeltplan ze een positieve en de seizoensgebonden impact hebben op waterbehoef-

de bodemstructuur wat infiltratie

+ Bodembedekking moet

ten

bevordert.

+ Er is nood aan een goede waterhuishouding om alle gezaaide soorten te laten vestigen

KOPPELKANSEN KNELPUNTEN

VARIANTEN FINANCIEEL

+ Erosiebestrijding + Nood aan een goede afzetmarkt + Groene of gebruik van de teelten in rantsoenen

+ Bodemtextuur + Nood aan aangepaste machines

€

bodembedekkers

+ Biodiversiteit + Nood aan kennis + Grasklaverteelt

+ Akker kan worden + nabegraasd Nood aan inpassing in de + bedrijfsvoering

Zwartstrook naar grasstrook

(fruitpercelen)

+ Onkruidbestrijding

+ Mengteelt

RUIMTELIJKE RANDVOORWAARDEN

+ Alsvoorbereiding graslandvernieuwing

een goede structuur met een goede ontwatering, tenzij er aan palu-

+ Er is nood aan een bodem met

dicultuur gedaan wordt

KOPPELKANSEN VARIANTEN FINANCIEEL

48–49

© Eddy Vanschoenwinkel

LONG TERM (10-20y)

+ Voedselproductie

+ Koolstofopslag

+ Droogte-resistente teelten

+ Verbreden teeltrotatie

+ Strokenteelt

+ Klaver, luzerne...

+ Natte teelten

+ Mengteelten

€ € €

5 Re-sponging Europe

20°

15°

250 500 750 km

10°

5°

0° 5°

10° 15°

20° 25°

30° 35°

55°

55°

50°

50°

A mission-driven approach

for sponge landscapes

45°

45°

The initiatives gathered in this workroom demonstrate

that we can define targets that trigger positive sponge

loops, align sponge measures in a basin-wide strategy

and build the necessary sponge coalitions.

40°

40°

Whether from policy or the ground, from wetland restoration

or resilient agriculture, pioneering initiatives

across Europe render us hopeful. They are active in

a great variety of European sponge landscapes, from

‘water batteries’ to ‘mossy rocks’ across different climate

conditions.

10°

5°

0° 5°

10° 15°

20°

However, some questions remain across the continent:

how do we get sponge measures embraced, replicated

and sustainably financed? As an integrator, the sponge

landscape is both the answer and the challenge. We

need an acceleration that brings the large-scale transformation

of our landscapes into reach.

We see both fragile and more established experiments

on at least four dimensions. They make up the building

blocks of a mission-driven approach for implementation. 52–53

1

Mission-driven sponge deals

An interactive process integrates sectoral targets in a

place-based deal between ‘goalkeepers’ and ‘sponge

coalitions’. A co-created deal in two steps: The first sets

a multi-targeted, measurable and time-bound direction,

based on modelling a puzzle of sponge measures tailored

to the sponge capacity of the territory. The second

transforms a plan into a framework of implementation,

defining roles and responsibilities.

GOALS

2025

X %

Y HA

Z M3

GAP

DEAL

PLAN

DEAL

TASKS

2050

VR 2025 1407 DOC.0663/2BIS

4 februari

2025

Document left: The Blue Deal Note 2025–2029 sets out the direction of water

policy in Flanders. It commits to supporting interlocal collaboration through the

experimental instrument ‘Local Blue Deal’: a partnership and contract between a local

coalition and Flemish authorities to jointly define integrated targets at the level of a

sub-basin, translate them into an integrated action plan and implement this plan.

Document right: In 2022 the Dutch National Rural Area programme planned a placebased

and integrated transformation to achieve targets on nitrogen, biodiversity,

water and climate. When the programme ultimately fell through, three agricultural

collectives launched their own initiative. They proposed a bottom-up ‘Gebiedsofferte’, 2—2

a ‘territorial quote’ outlining a spatial and financial plan of measures responding Positie to van de

the set targets as an offer to the government.

ambitienota in reeks

van documenten

Het project Noord-Zuid Limburg

wordt aangepakt volgens de

procedure complexe projecten.

Het proces volgt deze vastgestelde

methodologie met als doel succesvolle

afwikkeling van het project

te garanderen. Binnen die methodologie is er nog steeds een vrijheid voor

invulling. De ambitienota is één van de aanvullende documenten op de geijkte

documenten uit de procedure complexe projecten. In de onderzoeksfase

van het project zullen volgende documenten opgemaakt worden:

00 PROCESNOTA De procesnota is een aparte, opzichzelfstaande nota die het

volledige planningsproces omschrijft, zowel hoe het proces wordt gepland als

hoe het effectief werd uitgevoerd. Document 00, is dus een evolutief document

en vormt een leeswijzer van de doorlopen planningsprocedure en de

vervolgstappen.

01 AMBITIENOTA Na grondig (ontwerpend) onderzoek van de projectscope

en gesprekken met een breed stakeholderveld worden gedragen ambities voor

het verdere project opgetekend. Zoals hierboven toegelicht, zal deze nota het

basisdocument vormen bij het valideren van het ontwerpend onderzoek naar

toekomstbeelden en alternatieven.

Blue Deal 2025-2029

Kompas voor een waterwijs Vlaanderen

Blue Deal Note 2025–2029.

14 juli 2025

© Flemish government, on the proposal of Flemish

Minister for the Environment and Agriculture Jo

Brouns and Flemish Minister for Mobility, Public

Works, Ports and Sport Annick De Ridder

Ambition note North-South Limburg.

vlaanderen.be

© Studio NZL (Tractebel, Arcadis, Maat-ontwerpers,

51N4E, Nu-architectuuratelier, UHasselt), De

Werkvennootschap and the Flemish Department of

Environment together with stakeholders, may 2019

2—3

Auteurs van de

ambitienota

Gebiedsofferte BoerenNatuur

Groningen West

Zowel in de samenwerking tussen

opdrachtgevers en het onderzoeksteam,

als in de samenwerking met

de stakeholders wordt openheid

als een sleutelbegrip gehanteerd.

Het onderzoeksproces werd, zoals uitvoerig omschreven in de procesnota,

dan ook echt vormgegeven rond verschillende Gebiedsofferte BoerenNatuur manieren van dialoog en

samenwerking zoals de werksessies, verschillende Groningen West, bilaterale 2025. gesprekken én de

cocreatieweek, maar ook het veldwerk

©

van

BoerenNatuur

de Universiteit

Groningen

Hasselt.

West

Pagina | 1

Door deze open werkmentaliteit van bij de aanvang van het project in te

stellen, wil het onderzoek in een vroeg stadium op zoek gaan naar gemeenschappelijke

belangen en gedeelde ambities. Rond ‘leefbaarheid’ en rond

‘mobiliteit’ bestaan aparte gemeenschappen van experts, opiniemakers en

betrokken burgers. Beide thema’s zijn historisch en disciplinair anders samengesteld.

Het samenbrengen van thema’s maakt het voor eenieder noodzakelijk

om zijn of haar conventies te herzien. Het ontwerpend onderzoek wordt

daarom ingezet om dialoog op gang te trekken en ruimtelijke mogelijkheden

te verbeelden. Op die manier wordt ruimte gecreëerd om kansen op te

sporen en stimuleren tot samenwerken. Met als doelstelling een gezamenlijk

referentiekader op te bouwen waaraan de diverse toekomstalternatieven getoetst

kunnen worden. Het sluitstuk van het onderzoekstraject van november

2

Implementation-driven sponge facility

The sponge facility is the implementation-driven workspace

that brings together competences from the reality on the

ground, policy entrepreneurship and practice-based scientific

innovation. It acts both as a learning environment across

pioneering river basins and as an incubator for the next

pioneers. The sponge facility organizes the integration of space,

sectors, policy, capacity and funding while co-creating the right

strategic-political conditions.

02 ALTERNATIEVENONDERZOEKSNOTA (*) In de alternatievenonderzoeksnota

worden verschillende SUPRALOCAL alternatieven gedefinieerd die in een volgende fase verder

in detail onderzocht worden. Elk alternatief omvat keuzes op strategisch

niveau met betrekking tot duurzame mobiliteit en ruimtelijke ontwikkeling.

Daarnaast omschrijft de alternatievennota ook op welke wijze de effecten

ervan zullen worden onderzocht.

FACILITY

03 SYNTHESENOTA Deze nota omvat de ontwerp eindresultaten van het geintegreerd

onderzoek voor alle onderzochte alternatieven. Op basis van deze

resultaten worden bepaalde LOCAL alternatieven opzijgeschoven, tot er uiteindelijk

één oplossing overblijft. Dit vormt het voorwerp van het voorontwerp van

voorkeursbesluit.

04 VOORKEURSBESLUIT (*) Het doel van de onderzoeksfase is te komen tot

een gedragen ontwikkelingsvisie die fungeert als inhoudelijk en operationeel

Figure below: The Complex Project North-South Limburg started as a major

toetsingskader voor toekomstige projecten. Het project NZL inclusief flankerende

maatregelen wordt uitgevoerd door De Werkvennootschap en het

infrastructure and mobility project to connect Hasselt and Eindhoven, but evolved into

Departement Omgeving, maar evengoed andere projecten worden uitgevoerd

an ambitious transformation plan – even strengthening the natural system of stream

door ANB, AWV, VLM, Provincie Limburg, lokale besturen, enzovoort. In

valleys. The level of integration of the plan is a direct result of years of coordinated

het voorkeursbesluit wordt voor dit alternatief een breed pakket aan maatregelen

benoemd en worden verantwoordelijkheden per actor en partner

research and efforts – with a dedicated ‘werkvennootschap’ (working company)

bringing various regional departments together and a ‘Studio NZL’, a multidisciplinary

duidelijk aangeduid en engagementen geformaliseerd.

design-team.

Enkel de documenten met een (*) zijn formeel vereist.

54–55

Politiek overleg

Vlaamse regering

Stuurgroep

procesbegeleider

Onderzoeksteam (*)

Lokaal expertenpanel

Ambtelijke actoren

Actorenoverleg

Co-creatieweek

Werksessies

Onderzoeksteam (*)

De Werkvennootschap

+

Departement Omgeving

+

Studio NZL

Auteurs van

de ambitienota

Figure above: After the 2021 floods, a sustainable redevelopment programme was

set up to support resilient reconstruction across the seven affected municipalities

in the Vesdre valley. To facilitate its implementation, the post-flood reconstruction

team designed a governance model that pools the capacities of municipalities and

regional authorities within a dedicated reconstruction cell. This cell coordinates

projects and investments, enabling both the acquisition of the most vulnerable plots

and their exemplary and integrated transformation as ‘Structuring Projects’.

Figure center: With a view to accelerating open-space projects in Flanders, the

Open Space Platform developed its own programmatic approach: local coalitions

realize similar open-space projects in a learning environment, supported by a

programme team that provides integrated knowledge, tools and funds – pooling

resources for a multiplied impact.

3.1. HYPOTHÈSE DE LA RECONSTRUCTION SANS MODÈLE DE GOUVERNANCE

SCENARIO 0

COMMUNE 1

Projet structurant :

Autres projets :

Acquisitions foncières :

Autres acquisitions foncières :

COMMUNE 2


Autres projets :



COMMUNE 3


Autres projets :



...


Autres projets :



€

€

€

€

€

€

€

€

€

€

€

€

€

€

€

€

Administration

Collège

Administration

Collège

Administration

Collège

Administration

Collège

GOUVERNEMENT

WALLON

SPW - DAL

SPW - ARNE

SPW - MI

SWL

AUTRES ACTEURS

Volet 5

«Service après-vente»

Marché public de 3.2. services UNE de GOUVERNANCE programmes de RÉGIONALE ARTICULÉE Pouvoir adjudicateur: À UN PORTAGE DE PROJET Bureaux LOCAL d’études:

(re)développement durable des quartiers

Direction de l’Aménagement Local

(DAL)

PROJET

COMMUNE 1


Autres projets :



€

€

€

€

Administration

+ Collège

CHEF DE PROJET

COMMUNE

GOUVERNEMENT

WALLON

Secrétariat général

rapport

semestriel

GOUVERNANCE

TASK FORCE

ADMINISTRATION

Référent SPW - DAL

€?

p. 10

Governance scheme of the programme implementation, without or

without a project-driven reconstruction cell.

© Public service contract for sustainable (re)development programmes for

neighbourhoods by MSA, Taktyk, GRAU, Aries, IDEA Consultants, SBE for

the Direction of Local Land management, Walloon Government

Scheme programme approach, Operation Open Space.

© Architecture Workroom Brussels for the Open Space Platform

COMMUNE 2


Autres projets :



COMMUNE 3


Autres projets :



€

€

€

€

€

€

€

€

Administration

+ Collège

CHEF DE PROJET

COMMUNE

Administration

+ Collège

CHEF DE PROJET

COMMUNE

Coordination

mensuelle

CELLULE DE

RECONSTRUCTION

Durée opérationnelle :

3 ans

Coordination

trimestrielle

Référent SPW - ARNE

Référent SPW - MI

Référent SWL

€?

€?

€?

...


Autres projets :



€

€

€

€

Administration

+ Collège

CHEF DE PROJET

COMMUNE

CHEF DE PROJET

BOUWMEESTER

- 1 Communication

- 2 Urbanistes

- 1 Economiste

INTEGRATION

AUTRES ETUDES

Schéma stratégique Vesdre

Etude hydrologique Vesdre

Référentiels

Etc

AUTRES ACTEURS

€?

challenges

Marché public de services de programmes de

(re)développement durable des quartiers

Volet 5

«Service après-vente»

Pouvoir adjudicateur:

Direction de l’Aménagement Local

(DAL)

Bureaux d’études:

GOUVERNANCE

p. 11

available

budget

programme

approach

area-specific

approach

call

3 Outcome-oriented sponge instruments

Outcome-oriented sponge instruments facilitate the collective

implementation, maintenance and monitoring of measures that

activate many sponge loops. Rather than compensating for

losses on individual plots, they steer a territorial transformation

that delivers on several targets at once. The motto and lever of

the public sector is: to stimulate and incentivize where possible,

to intervene on the most strategic locations in the basin where

necessary.

SPONGE

Classification plan for the district for

allocating shared water management costs

© Consorzio di Bonifica Pianura di Ferrara

Toolkit of instruments.

© Flemish Land Agency, Flemish government

Document bottom left: The Po valley faces significant flood and drought challenges.

In reaction to this, a consortium of four polder boards across the valley set up a

dual compensation system. On the one hand, land users pay a three-tiered financial

contribution according to their water demand, taxing farmers with more waterintensive

crops. On the other, downstream farmers with more flood-prone lands get

an annual compensation calculated on the basis of the most desirable crop, namely

grassland.

Figure bottom right: Since 2014, the Land Use Planning Decree has included a toolkit

that enables the Flemish government, provincial authorities and municipalities to

organize land mobility. The toolkit is structured in three categories, with instruments

such as land consolidation and land exchange; instruments to deliver public services

on private land, such as development works and management agreements; and

instruments to facilitate projects, such as a land bank and business relocation.

56–57

CONSORZIO DI BONIFICA

PIANURA DI FERRARA

Via Borgo dei Leoni, n. 28 – 44121 Ferrara

PIANO DI CLASSIFICA

DEL COMPRENSORIO

PER IL RIPARTO DEGLI ONERI

CONSORTILI

____________________________________________________________

Approvato in via definitiva con Deliberazione della Giunta Regionale n. 2234 del 28/12/2015 e con

deliberazione del Consiglio di Amministrazione n. 1 del 25/1/2016

INRICHTING

Inrichtingswerken

Inrichtingswerken uit

kracht van wet

Vergoeding voor

waardeverlies van

gronden

ANDERE

Lokale

grondenbanken

(incl. vergoedingen)

Vestigen van

erfdienstbaarheden

tot openbaar nut

Vrijwillige

bedrijfsverplaatsing,

bedrijfsreconversie en

bedrijfsstopzetting

Koopplicht

BEHEER

Beheerovereenkomsten

Dienstenvergoeding

VERWERVING EN GRONDMOBILITEIT

Verwerving

Projectmatig recht

van voorkoop

Vrijwillige

herverkaveling

Herverkaveling uit

kracht van wet

Gebruiksruil

Herverkaveling uit

kracht van wet met

planologische ruil

Just Water Partnerships: Framing note on Concept and Principles

(Draft for discussion purposes)

4 Integrated sponge investments

Rather than allocating budgets across sectors and then seeking

cooperation and additional private funding, the logic is turned

upside down. We need to finance the ripple effect that leads to

basin-wide, co-created transformation. Mission-driven sponge

deals and outcome-oriented public engagement are the

essential conditions to activate both private and philanthropic

funding around targeted sponge investments.

POOLED

CAPACITIES

RO

PHILANTHRO

PUBLIC

RE:SPONGE EUROPE

JWP

ATE

R

AT

PIC

PRIVA

V

Rough outline of logic of soil-water as infrastructure.

© Kjell Clarysse — Natural Infrastructure

€

€

+

€

+

€

– Risk contamination

– No financial value of soil-water

– Perverse incentive to not innovate

= Develop soil water storage as a

financial infrastructure

2

PROPCO

1

OPCO

Figure above: Externalities, and the financial value they generate, are often missed

on the balance sheet. Natural Infrastructure explores how water in the soil beneath

farmland can be financially recognized as core infrastructure, seeing that a stable

landscape has much higher economic value. Soil-water infrastructure is isolated

in a dedicated sponge vehicle, making it an asset in the balance sheet. It enables

stakeholders to interact with this water infrastructure capacity by paying for water

availability on a farm level and towards downstream dependents.

Article: Within ‘Business for Nature’, nature organization Natuurpunt is looking

for co-investors to fund the land acquisition of missing links in wetland restoration

projects around the city of Mechelen. In exchange, investing companies can get

a fun, tailor-made team-building experience while contributing to a healthy and

climate-resilient environment. More than 35 companies, representing a total of

150,000 euros, have already invested in the purchase of a strategic piece of land.

Document bottom right: The Global Commission on the Economics of Water,

together with a diverse group of eminent policymakers and researchers, advocates

for a shift in how water is valued, managed and governed by calling for Just Water

Partnerships. These partnerships aim to provide a platform that matches financing,

governance and investment with equity and sustainability at the heart of decisionmaking

and resource allocation. They propose a new financing model that mobilizes

both public and private capital to support a just water transition.

Article from De Tijd on Natuurpunt’s approach.

© De Tijd, Floor Eelbode, 4 October 2025

wins on positive externality

landscape-wide resilience

village

GOVERNMENT

INSURANCE

avoids flood damage

anti-erosion

anti-flood

water availability in

dry-season

farm downstream

2

3

AGRO

1

PROPCO

HYDROCO

OPCO

flood buffering

drought control

erosion control

€

soil improving

practices

OUTPUT

3

financial

horizon

1-5 years

10-20 years

5-20 years

HYDROCO

FOOD

INDUSTRY

more constant

conditions in

supply chain

= resilience

= dedicated sponge vehicle

Just Water Partnerships: Framing note on concept

and principles.

© WaterAid, International Water Management

Institute and the Global Commission on the

Economics of Water, July 2025

Just Water

Partnerships:

Framing note

on concept and

principles

(Draft for discussion

purposes)

July 2025

WaterAid

International Water Management Institute

Global Commission on the Economics of Water

58–59

July 2025 |

1

Europe’s sponge landscapes

20°

15°

250 500 750 km

10°

5°

0° 5°

10° 15°

20° 25°

30° 35°

North Water Tower

Boreal Mossy Rocks

55°

55°

Western Mossy Rocks

50°

Atlantic Shallow Lands

Baltic Shallow

Lands

The Big Water Battery

50°

45°

Atlantic Hidden Well

Alpine Water Tower

Central Mossy Rocks

Central Hidden Well

45°

One Small

Water Battery

40°

The other Small

Water Battery

Iberian Water Towers

Mediterranean Mossy Rocks & Hidden Wells

40°

Europe’s sponge landscapes are rich and diverse. If

we want to maximize sponge capacities across the

continent, we must recognize the specificity of each

landscape, and its unique interplay between deep

hydrogeology, topography, topsoils, landwateruse and

even green water flows.

At the same time, combining these layers together, we

can roughly identify five distinctive ‘families’ of sponge

landscapes. Together, they pave the way for us to learn

across borders, climates, and cultures and transform

Europe’s river basins to resilient sponge landscapes!

This map was produced as part of the open workroom SPONGE LANDSCAPES, based on GIS data on the

hydrogeology, land use, topsoil and topography of Europe. © Architecture Workroom Brussels

Sources

Hydrogeology: International Hydrogeological Map of Europe 1:1,500,000 (IHME1500) © BGR & UNESCO (eds.), 2019.

Land use: Coordination of Information on the Environment (CORINE) Land Cover Map © Copernicus Land Monitoring

Service, European Environment Agency (EEA), 2018.

Topsoil: Topsoil physical properties for Europe © Ballabio C., Panagos P., Montanarella L. Mapping topsoil physical

properties at European scale using the LUCAS database (2016) Geoderma, 261 , pp. 110-123.

Topography: Digital Elevation Model Europe (EuroDEM) © EuroGeographics, 2025.w

60–61

10°

5°

The Water Batteries

Water Batteries have sandy, well-drained soils and rather

flat, open landscapes. Rainwater easily seeps into the

ground, enabling them to hold and large amounts of water.

However, if water drains too quickly into deeper layers,

the topsoil dries out rapidly. Water batteries are therefore

susceptible to drought, particularly when groundwater

levels drop or the land is heavily drained.

The Mossy Rocks

The rocky subsoil of Mossy Rocks largely precludes deep

water storage. These areas are often located upstream and

are historically characterized by extensive grasslands or

dense forest cover. In the Mossy rock, it’s the vegetation

holding the water and taking up the sponge function, rather

than soil and aquifers below.

The Shallow Lands

0° 5°

10° 15°

20°

Shallow Lands are flat, low-lying, or reclaimed areas with

an impermeable but fertile clay topsoil, combined with

very shallow aquifers. The sponge capacity for storing

water underground is therefore minimal. Careful water

management and control of water levels are necessary to

prevent flood risks and ensure enough water for all land uses.

The Water Towers

Europe’s mountains are the sources of many of our great

rivers. Their rocky subsurface leaves little room for storing

water underground, but the snow, ice, and permafrost found

on the peaks and glaciers act as natural sponges in their own

regard, slowly releasing water over time.

The Hidden Wells

Hidden Wells are more gently sloping or hilly areas with

diverse fertile soils made up of löss, loam, sandy loam, or

clay. Some of these layers let water pass through easily,

while others hold it back. The deeper ground is just as

mixed, with both porous and dense layers that can actually

store large amounts of water. But the rather impermeable

topsoils hide these underground wells, making the water

drain away quickly at the surface. Whether water has

enough time to infiltrate into deeper groundwater layers

largely depends on how the land is used and managed.

This cahier documents the ‘open workroom

SPONGE LANDSCAPES’, an initiative and production

of Workroom vzw. The initiative is part of a series

of ‘open workrooms’ that Workroom is organizing

around the transformations it has committed itself

to for 2023–2030: energy neighbourhoods, sponge

landscapes and new community infrastructures.

The open workroom SPONGE LANDSCAPES is

inspired by the 86 submissions to the international

Call for Projects & Objects. Both exhibition and

public programme draw from and contribute to the

ambitions of the Open Space Platform, the Blue Deal

2025-2029, the report on The Economics of Water –

Valuing the Hydrological Cycle as a Global Common

Good and the EU Water Resilience Strategy.

CURATORIAL & RESEARCH TEAM

Workroom

Lene De Vrieze

Bram Vandemoortel

Leonie Martens

Hannah Nelis

Francis Schoups

Joachim Declerck

Weronika Kozak

QUALITY COMMITTEE

Griet Celen,

Flemish Land Agency

Joep Fourneau,

Regional Landscape Haspengouw & Voeren

Sarah Garré,

Flemish Institute for Agricultural, Fisheries and Food Research

Henk Ovink,

Global Commission on the Economics of Water,

International Water Management Institute

Ine Soenen,

Province of West Flanders

David Verhoestraete,

CLUSTER landscape & urbanism

Patrick Willems,

KU Leuven

PRODUCTION COORDINATION

Workroom

Caroline Van Eccelpoel

EDITORIAL & PRODUCTION SUPPORT

Kaat Langenaken

Elise Livens

GRAPHIC DESIGN

Studio de Ronners

Lieselot Coenen & Robbert Liekens

TRANSLATION & COPY-EDITING

Patrick Lennon, English

Nicky Wijns, Dutch

Alain Kinsella, French

VISUAL MATERIAL

© Workroom unless otherwise stated

EXHIBITION IMAGES

Bob Van Mol

Ivan Put

We Document Art

PRINTING

Antilope De Bie

PARTNERS

The Global Commission on the Economics of Water

The International Water Management Institute

REWORLDING doctoral network, UHasselt

Flemish Land Agency

Flanders Environment Agency

WITH THE SUPPORT OF

Flemish Government

Department of Culture

Flemish Land Agency

Flanders Environment Agency

V.U. & PRODUCTIE

Workroom vzw

The mission-driven approach described in chapter 5 is inspired by the work of Prof. Mariana Mazzucato

(Co-Chair of the Global Commission on the Economics of Water and Professor at University College

London, where she is the Founding Director of the UCL Institute for Innovation and Public Purpose).

SPECIAL THANKS

For contributions to the exhibition

Annelies De Nijs (Atelier Horizon), Bob Van Mol, Thibaut Joris and Simon Servaes (Bos+), Hiske Zomer and

Ellen De Naeyer (BRONKS), Chantal Bisschop and Laura Danckaert (Centrum Agrarische Geschiedenis),

Aurore Degré and Adrien Michez (ULiège — Gembloux Agro-Bio Tech), Katrijn Loosveldt (Stad Kortrijk),

David Verhoestraete and Andreas Bauwens (CLUSTER landscape & urbanism), Jan Lippens (Coördinatie

Zenne vzw), Ellis Penning (Deltares), Giacomo Laghetto (Etifor), Carmen Van Maercke and Michaël Stas

(fallow), Liesl Vanautgaerden (Departement Omgeving), Jasper Hugtenburg, Jaap van der Salm and

Hestia Zinsmeister (H+N+S Landschapsarchitecten), Hettie Meertens (ARK Rewilding), Wouter Igodt

and Jente Lezy (HelloWater), Eric Brinckmann (Het Lankheet), Hedwig Hoppenbrouwers and Jorryt

Braaksma (LAMA landscape architects), Lieven De Stoppeleire (Landschapspark Vlaamse Ardennen),

Andrea Aragone and Octavio Pineiro (LATITUDE Platform), Charlotte Jacobs, Giulia Ravera, Filip Buyse

(MAAT ontwerpers), Marjolijn Claeys, Benoit Moritz (MSA), Nils Iwens (Natuurpunt), Kjell Clarysse (Natural

Infrastructure), Chloé Déchelette (OiEau), Hans Druart and Hicham Karkouch (OMGEVING), Eva Pfannes

(OOZE Architects & Urbanists), Koen Eyskens (Provincie Antwerpen), Marie Van Loon and An Steegen

(Provincie Vlaams-Brabant), Steven Beyen (Provincie Limburg), Ine Soenen (Provincie West-Vlaanderen),

Joep Fourneau and Christel Cornelissen (Regionaal Landschap Haspengouw & Voeren), Etienne Schillers

(Studio Paola Viganò), Amélie Fietier (Fondation Rurale Interjurassienne), Jan Staes and Lander Neuskens

(Universiteit Antwerpen), Aurore Degré (Uliège — Gembloux Agro-Bio Tech), Markus Schwegler Meierhans

(NaturGut Katzhof), Lieven Symons (Waterland vzw), Linde van Bets (Wing)

For the brainstorms on ‘Europe’s sponge landscapes’

David Verhoestraete, Patrick Willems

© 2026, Workroom vzw

All rights reserved

ttery

ly permeable subsoil

catchment area

There is a space that defines the future

of food production, water security and

biodiversity. A space that can help to

restore the global water cycle and mitigate

climate change: SPONGE LANDSCAPES.

Activating the natural sponge function of

landscapes offers a hopeful and integrated

response to the growing impacts of

drought and pluvial flooding periods. This

is demonstrated by the pioneering work

of regional coalitions, farmers, nature

organizations, water managers, scientists,

designers, policymakers, and organizations.

H

loa

ba

However, they are facing an

implementation gap. If we continue to work

per sector, target and parcel, it is certain

that the intended goals regarding water

quality, quantity, and nature restoration will

remain out of reach.

SPONGE LANDSCAPES therefore stand for

a shift in how we manage water and land.

From rapidly evacuating water to retaining

every drop where it falls. From making

room for the river to activating the sponge

function across the entire river basin. And

from accepting the landscape as the sum

of sectoral, often conflicting actions to

organizing its coherent transformation.

By sharing our experiences and combining

our efforts, we can draw an enabling

framework for the coordinated, timely

and appealing transformation of Europe’s

sponge landscapes!

This cahier brings together the work

exhibited in the ‘open workroom

SPONGE LANDSCAPES’, an exhibition and

programme that ran from November 20,

2025, through June 12, 2026.

ISBN 978-9-08195-356-6

s

rmeable subsoil

asin

M

gra

sub

open workroom SPONGE LANDSCAPES - cahier EN

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