Strand 5: urban drainage Flashcards
What is urban drainage
Built-up areas need to be drained to remove surface water runoff. Traditionally this has been achieved by using gullies and underground pipe systems designed to convey the water away as quickly as possible.
What are the issues of drainage in urban areas
-no infiltration
-little interception
-lack of permeable land
-lots of surface run off
-impermeable ground
-cities get 15% more rain then rural areas
What does a hydrograph look like in urban areas
-short lag time (water moves quickly form falling to rivers via drains)
-river levels increase incredibly quickly
-high peak discharge
What does a hydrograph look like in rural areas
-low peak discharge
-long lag time
What are SUDS
A sequence of water management practices and facilities designed to drain surface water in a manner that will provide a more sustainable approach then what has been the conventional practice of routing run off through pipe/drains to a watercourse
Types of SUDS: permeable pavements
Materials such as asphalt or crushed stone. The water infiltrates directly and can be stored in a underground resovoir. It removes the pollutants from the water
Types of SUDS: Swales/basin
-these are landscaped and can be ornamental and planted to maintain an aesthetic. S/B are often installed with pipes for overflows (similar to ditches). They drain slowly as there is a layer of rock underneath, this takes out the pollutant and goes into the pipe lines
Types of SUDS:green roofs
Green roofs reduce peak flow and improve water quality. It can be collected and used for flushing toilets. Can be done on existing buildings
Types of SUDS: ponds/wetlands
They are designed to be attractive and store large amounts of water
Types of SUDS: infiltration trench
They collect the water and are widely used due to the ability to remove pollutants due to gutters. Roads are built on a curve, the curbs have holes in them and the water filters through into the river
Case study: alcester care centre
-rain garden. Planted a swale and use hedgerow and trees
-permeable pavements all around the centre. 0.75 hectares
