E
cosystem
servicesdelivered
Provisioning
Regulation & maintenance
Cultural
Abiotic
C
ontribution
topolicyobjectives
Water Framework Directive
Floods Directive
Birds & Habitats Directive
2020 Biodiversity Strategy
P
otential
biophysicaleffects
Runoff
Reducing pollution
Soil conservation
Habitat
Climate Change
High
Low
Medium
None
One of the primary purposes of overland flow areas is to
store runoff
. Storing runoff on land allows
sediments
to be deposited, which can help to prevent sediment pollution
of downstream receiving waters. Slower water flowing over rougher environments (terrestrial vs. ditch) will also facilitate the deposition of suspended material. Sediment-related
pollutants
including phosphorus and heavy metals will be filtered out and deposited onto land. Preventing sediment inputs to receiving lakes and streams may help to preserve
spawning or pearl mussel
habitat
. This would help to maintain fish stocks. Thereby, overland flow areas can help to prevent deterioration of surface water bodyWFD status and
make forestry more
sustainable
as they can limit some negative impacts associated with sediment pollution.
There is a potential for overland flow areas to increase soil water retention and infiltration as they retain water on the landscape instead of routing it directly to ditches or
streams. However, the effects are likely to be moderate as overland flows typically occur when soils are at their wettest. Peak flow control structures can have a moderate effect
on water storage. Typically, the effect is quite local and short lived but it may be sufficient to mitigate some flood peaks during spring runoff. As such, overland flow areas can
make a
limited contribution
to reducing flood risk.
