Urban Drainage Flashcards
Infiltration and run off in urban areas
Urban areas are covered in impermeable surfaces so infiltration is low and groundwater stores are low making river discharge also low. Precipiation is higher in urban areas so run off is high. This gives a short lag time and high peak dischsarge
Catchment management
Catchment management is a way of managing rivers and improving drainage systtems by looking at thw whole river catchment. It aims to minimise flooding drought water pollution and erosion in sensitive areas to improve river ecosystems
Hard engineering
involves man made structures such as dams floodwalls and reservoirs which are used to prevent flooding and ensure a constant water supply. However can be expensive and can disrupt natural systems
Soft engineering
Uses knowledge of the river basin and its processes to try to work with nature. eg planting trees to decrease flood risk and preventing building on the floodplain. it can involve river restoration. It is generally cheaper and can improve the local environment
SUDS make urban drainage more sustainable - what are they?
SUDS represent realistic and environmentally friendly replicas of natural drainage systems. They hold back and slow surface run off and allow natural processes to break down pollutants
Benefits of SUDS
creating green space
prevents water pollution
provides habitats
increased biodiversity
reduced flood risk
improved air quality
Green roofs
Multi layered system that covers the roof of a building with vegetation cover to intercept and retain precipitation to reduce run off and peak flows.
+ improves air quality
+ manages urban heat island
- costly
Swales
Vegetated trenches in the ground to increase interception of rainfall and store it which lowers flood risk
+ increase biodiversity
+ improves air quality
Pervious surfaces
Can be permeable or porous and water can be temporarily stored before infiltration.
+ reduced peak flows
+reduced effect of pollution
- risk of long term flooding
Rain gardens
Small depressions in the ground that can act as infiltration points for roof and surface water
+ easy to maintain
+ small so minimal land take
- can be clogged
Wetlands
Comprise of shallow ponds and marshy areas covered almost entirely in aquatic vegetation. They detain flows for extended periods.
+ aesthetic and amenity benefits
+ good community acceptability
- high land take
CASE STUDY - Lamb Drove, Cambourne
Located west of Cambridge where Cambridgeshire is a relatively low lying county where flooding is a major concern. Original aim here was to showcase practical and innovative sustainable water management.
SUDS used - water butts to collect roof water, permeable paving, green roofs, swales, detention and retention ponds and wetlands
Proven successful having been monitored and appraised since completion in 2006. It is cost effective and there has been substantial improvement in biodiversity, ecology and quality of life
