Roadside Revegetation

PLANNING PHASE TWO: ASSESS SITE
returned to the atmosphere through evaporation. During the dry season, moisture from a
low rainfall event might not reach the soil.
Figure 5-5 | Fill slope microcatchments
Fill slope microcatchments take advantage
of the low infiltration rates of compacted fill
slopes. Water moves off impervious road surfaces
and compacted road shoulders during
rainstorms (A), and is captured in berms or
flattened areas below the road shoulder (B). If
this area is ripped and amended with organic
matter (e.g., filter strips, amended fill slopes),
it becomes a very good environment for
establishing shrubs and trees. Berms and/
or flattened areas are also catchments for
sediments.
Figure 5-6 | Planting pockets
Planting pockets are designed to capture
water from upslope runoff (A), that collects in
a slight depression (B). Captured water wets
the soil after each rainstorm and drains into
the fractured bedrock (C). Soil is protected
from surface erosion on the downhill side of
the pocket with mulch or erosion fabric (D).
Rainfall Interception – How to Assess
Rainfall interception can be determined by the soil cover and vegetation that exist on the
site after construction. In most cases, there will be very little vegetation and ground cover.
It is therefore important to understand the effects of various types of ground cover used in
revegetation on the rainfall interception. The depth and water-holding capacity of the material
will determine the effect on water input.
Water-holding capacity of a surface cover can be measured through testing labs specializing in
composts. Alternatively, it can be measured by collecting the soil layer (duff, litter, mulch) and
drying it at 230° F in a drying oven (a crockpot can be used, adjusting the temperatures using a
meat thermometer). When the sample is dry, it is placed in a 5-inch-long by 3-inch-round PVC
pipe with a flat piece of cardboard secured to the bottom of the tube to prevent the material
from falling out. The PVC pipe is weighed and placed in a bucket that is filled with water to
the top of the pipe. The sample is removed and allowed to drain.
After several hours the pipe is reweighed. The material in the pipe is removed and the pipe
plus cardboard is weighed. The moisture holding capacity of the material (by percentage of
dry weight) is as follows:
(wet weight – container & cardboard) - (dry weight – container & cardboard))/(dry
weight – container & cardboard)*100
Figure 5-7 can be used to approximate how much rainfall is intercepted based on the moisture-holding
capacity of the soil cover.
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
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