CLM20-2 full issue-1 - Flipbook - Page 7
Saltmarsh restoration through flash re-creation
precipitation, and being drained
by evaporation and percolation
into the soil. In some areas of
marsh the groundwater table
also supplies fresh water and
allows the development of more
organic soils than the typical siltdominated sediments. Flashes
are functionally important to
the marsh, not just because they
support still-water communities
but also because they have a
different ecosystem – typified by
low vegetation cover and high
invertebrate biomass. Owing
to the gradual loss of water
from the pools, their marginal
areas are often characterised by
sparsely vegetated drawdown
A digger working on flash re-creation. Bart Donato
zones (areas of ground exposed
as the water level drops) favoured by open-ground United States, it is rarely carried out in the UK,
except on a small scale to facilitate wildfowling.
invertebrates and wading birds.
Similar measures have been adopted on the
Historically, at least on the saltmarshes of
Continent as part of recovery plans for coastal
north-west England, many of these depressions
marshes where restoration of wader communities
have been drained by the installation of a footis the aim. On the Solway, the restoration of
drain network – hand-dug ditches that allow
water gathered in the lowest points of the flashes a the water-holding ability of the flashes has been
reinforced by other methods aimed at enhancing
direct pathway to escape to the creeks through an
wader productivity, including the development
incision in the raised bank. This was done because
of tailored grazing regimes to improve sward
the removal of temporary brackish pools, with
structure and the deterrence of terrestrial
their bare drawdown zones, allows vegetation
predators via physical barriers.
cover to increase, thereby providing a larger
area for grazing or turf-cutting. Drainage does,
however, have a significant impact on the function
Flash restoration
of the marsh surface. Instead of pools that are
In its simplest terms, flash restoration can be
filled by large tides and rainfall, a system becomes
thought of as plugging a leak and preventing
established in which tides are able to reach the
water – derived from tide or rainfall – from
marsh more often (via the incisions in the levees),
escaping the surface of the marsh. In our work
but the estuarine water and rainfall are lost as
we have employed two techniques, depending
the tide recedes. As a consequence, rather than a
on situation and constraints: the restoration
pattern of infrequent saturation with long periods
of former flashes and the creation of artificial
of water retention, the marsh is inundated more
ones that function as natural flashes would.
frequently but the water is then rapidly lost, often
In both cases, areas of past modification and
within hours after a high tide.
optimal areas for restoration have initially
Over the past decade we have undertaken works been identified by analysis of LiDAR data and
to restore a number of saltmarsh flashes on the
aerial photography (particularly Google Earth).
English Solway, particularly on Rockcliffe Marsh,
In many instances, the variation in surface
through remediation or adaptation of drainage
levels between the creek-edge levees and their
channels. Although this type of restoration is
associated flashes is minimal (between 10cm
regularly implemented on saltmarshes in the
and 20cm) and can be difficult to determine by
Conservation Land Management Summer 2022 | Vol. 20 No. 2 5
