CLM20-2 full issue-1 - Flipbook - Page 8
Saltmarsh restoration through flash re-creation
A newly created bund (background) constructed from sediment
obtained from the marsh, with pools filled by rainfall. Bart Donato
and can be tricky to see on
the ground when not holding
water; however, differences in
land level can be emphasised by
playing with the visualisation
of LiDAR data. While the
effect of blocking artificial cuts
through creek-edge levees is
similar to grip blocking in the
uplands, a key difference is that
the dams here must allow tidal
overtopping in order to fill the
flashes in the first place. Some
drains can be very small – little
more than hand-dug channels
– and thus can be remediated
by hand, but most are more
substantial and require a digger
to ensure that the blocks are
wide enough to hold back
water and that substrate has
been sufficiently compacted
to retain its structure. Where
larger areas of flash have been
drained it is important to
identify all the drains involved,
as some areas have multiple
drainage paths.
Creation of artificial
flashes
In some areas drains serve a
dual function: they enable flash
drainage and also allow water
A well bedded-in dam, four years after restoration works, remains
passage from inland areas to
visible owing to heavy poaching by livestock (dams are softer than
the sea. In these circumstances,
the adjacent marsh). Bart Donato
the blockage of drains is often
eye, although this can be more obvious where
not appropriate because of the impact on areas
differences in elevation are shown by changes in
upstream, so we have employed a different
vegetation communities.
approach that seeks to create naturalistic flash
structures alongside artificial channels. After
employing LiDAR to identify low-lying areas that
Flash restoration by remediation of
have been modified, we scraped the marsh surface
artificial drains
This is the most straightforward approach to flash adjacent to the ditch so as to define the footprint
of the flash. Any spoil generated was deposited
restoration, akin to the more common practice
between the flash and the artificial channel to
of grip blocking on moorland where small dams
form a low berm (c. 10cm high once settled)
help to retain water and rewet the soil. Using
along the drain edge, which functions as a natural
LiDAR to initially identify areas of interest
creek-side levee, ensuring that water in the flash is
allows subtle changes in land level to be detected.
prevented from escaping into the adjacent drain.
Many flashes are naturally less than 10cm deep
6 Conservation Land Management Summer 2022 | Vol. 20 No. 2
