Fen Management Handbook - Scottish Natural Heritage

9.7.2 Topography
The topography of a site and its height relative to surrounding land will largely
dictate the way in which water reaches the site and the type of fen that can be
created. Section 3: Understanding Fen Hydrology explains the different types
of fen, including those dependent on topography where the water movement is
predominantly vertical (topogenous fens) or those fed with the lateral movement
of groundwater (soligenous fens) or the often drier fen meadow. A fen may have a
combination of soligenous and topogenous characteristics.
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Topographical data gathering
Topographical information may be obtained from a number of sources.
– Lidar surveys provide course level data on land levels and
topography, which may help in the initial planning phases and
scoping of a wetland creation project. Statutory agencies such
as EA may charge for supply of data they hold, or this can be
purchased or commissioned commercially.
– Professional topographical surveys can be commissioned for a site
to provide more detailed data (e.g. up to 5 cm contour resolution).
Data will normally be supplied in electronic form for utilisation
in computer mapping and design packages and linked to GPS
co-ordinates. Costs will vary depending on terrain, survey spec,
accessibility etc. Example site, on ATV accessible, dry terrain, in
southern England cost approximately £40/ha, using a 20 m grid
producing 20, 10 and 5 cm resolution data.
– Simple spot height checks of relative high and low points, heights of
sluices/bunds etc. or basic surveys can be undertaken by site staff
with rented survey equipment such as auto planes or laser planes
at low cost. (e.g. £30-70/week). Some very basic understanding/
experience will be required.
– Winter puddle maps, vegetation maps, fixed point photography and
site visits can be the simplest method of obtaining basic information
regarding relative land heights, low spots prone to flooding etc.
Undertaking a
topographical survey
(N. Droy)