Elia Desmot, OIEau
Flood control areas as an opportunity to restore estuarine habitat. Ecological Engineering 28(1), 55-63.
Tuning the tide: creating ecological conditions for tidal marsh development in a controlled inundation area. Hydrobiologia 588, 31-43.
NWRM(s) implemented in the case study
cool temperate moist
Actual Test Site
Light or indepth?
Monitoring impacts effects
Accretion or erosion on site; tidal levels and velocities; creek morphology; suspended solids; soil nutrients; water quality (incl. metals); light climate; bioturbation; invertebrates; vegetation; birds; fish;
Performance impact estimation method
Design & implementations
< 1 year
Design capacity description
Scheme implementation was slowed by financial aspects and public opinion - consequently the project took a long time to materialise.
The scheme was made possible by a desire for integrated water management.
Design contractual arrangement
Design consultation activity
|Activity stage||Key issues||Name||Comments|
Design land use change
|Land use change type|
Lessons, risks, implications...
The Controlled Reduced Tide (CRT) technique employed at Lippenbroek has potential applicability for habitat creation along other heavily developed estuaries. It furthermore represents a technique which can significantly reduce the tidal prism of a site, without compromising the development of a range of intertidal habitats, thus minimising potential negative effects on small estuary systems. The technique also enables the establishment of intertidal habitats at lower elevations in the tidal frame than those of intertidal systems fronting a defence, and would thus be of potential use in areas where land levels behind a defence are relatively low compared to fronting levels. However, longer flood duration and low-turbidity stages may lead to higher accretion rates than in adjacent natural systems(ABPmer, 2008).
|Success factor type||Success factor role||Comments|
Attitude of relevant stakeholders
|Barrier type||Barrier role||Comments|
Attitude of the public
Lacking financing sources
|Driver type||Driver role||Comments|
Past flooding events
Loss of goods and services (loss of intertidal habitats)
loss of ecosystem functions (and thus loss of safety)
|Financing share type||Share||Comments|
Policy, general governance and design targets
Demonstration site, improved flood defence, habitat creation
Part of wider plan
|Pressure directive||Relevant pressure|
|Policy area type||Policy area focus||Name||Comments|
|Impact directive||Relevant impact|
Policy wider plan
|Wider plan type||Wider plan focus||Name||Comments|
Policy requirement directive
Ecosystem improved biodiversity
Information on Ecosystem improved biodiversity
With regards to birds, despite the high degree of disruption by humans (including site visitors,cyclists and walkers on the dike), a clear change in the numbers and species of birds using the site could be observed when compared to baseline conditions. Of the 4,089 individuals observed during the first year of monitoring, 30% were benthic foragers (19 species), 54% wetland-generalists (11 species), 8% terrestrial generalists (18 species) and 8% woodland birds (13 species). Occasionally night herons Nycticorax nycticorax and spoonbills Platalea leucorodia were observed feeding (Maris et al., 2008). In order for a CRT to fulfil a role for fish, safe passage of the cluvers/sluices is required.
Ecosystem provisioning services
Information on Ecosystem provisioning services
Ecosystem impact climate regulation
No specific impact
Information on Ecosystem impact climate regulation
Information on retained water
average water exchange volume: neap tide: ~4,000m3 (none on the lower neap tides)
Information on increased water storage
spring tide : ~40,000m3
Water quality overall improvements
Information on Water quality overall improvements
With respect to water quality, the oxygen enriching impact, which is mostly due to the high inlet sluices acting as aerators, has been described as †˜striking†™. At the sluices, an immediate increase of up to 60% has been observed and a further 20% enrichment has been attributed to surface oxygenation.
Soil quality overall soil improvements
Information on Soil quality overall soil improvements
Information on Soil quality, overall soil physical properties
Sedimentation was strongly related to flooding frequency; i.e. the highest sedimentation rate was observed at sites inundated around 85% of the time. The average sedimentation rate is currently fairly high at approximately 4 cm/year. The lowest sites are accreting fastest, hence the polder is loosing slope. Outside the polder, in natural marshes, an increase in elevation would lead to a decrease in flooding frequency, and a consequent gradual decrease in sedimentation. Conversely in the CRT the flooding frequency is not directly coupled to elevation; the intake volume is stipulated by the sluice configuration.