Urban Drainage (Unit 1, Topic 5) Flashcards
Urban Drainage in Urban and Rural Areas/ Fail to and Safe to Drainage Systems/ River Restoration in LA/ SUDS and their aims/ Types of SUDS and their Benefits.
What does the Urban Area do to Urban Drainage?
Shorter basin lag time- Impermeable surfaces lead to rapid overland flow resulting in a quicker transfer to the river
Steeper Rising Limb- Water Management Systems such as gutters and drains allow water to flow into the river quicker leading to high peak discharge
Steeper Falling Limb- There is less underground storage of the water will have entered the river and the base level will return quicker
What does the Rural Area do to Urban Drainage?
Longer basin lag time- Precipitation falls onto leaves and then drops to the ground. Some will infiltrate and therefore take longer to return to the river
Gentler Rising Limb- Moisture can also be absorbed and transpired by trees so less water reaches the river
Gentler Falling Limb- Water will return to the river after many hours as it flows through soil and rocks as groundwater flow. Taking it longer to return to the river at base level
What is a Fail Safe Drainage System?
Reducing problems that have occurred in the past
What is a Safe to Fail Drainage System?
Sustainable urban drainage systems and river restoration schemes that aim to last for long periods of time and prevent a problem from occurring in the first place
How has River Restoration impacted Los Angles?
In 1930 they channelized the river, removing habitats and wildlife but became extremely effective at preventing flooding.
The restoration project aimed yo restore 11 miles of the LA river, from Griffith Park to downtown LA. Much of the 51 mile long river functions as a storm drain channel. the plan would be to accommodate recreational and natural uses of the river while maintaining the city’s existing flood risk management levels
What are SUDS?
Sustainable Urban Drainage Systems are a relatively new approach to managing rainfall by using natural processes in the landscape to reduce flooding, control flooding and provide an amenity for the local community
What are the Main Aims of SUDS?
They aim to improve water quality, increase city greenspaces, more evapotranspiration and improving city biodiversity
How do Storm Plots improve Drainage?
They are used to determine the best surface for infiltration and reduces the pressure on drainage networks
How do Wetlands improve Drainage?
They are large open areas of grassland that have been implemented to allow for large scale infiltration and water pooling that doesn’t affect the surrounding urban area
How do Swales improve Drainage?
They channel water into a specific area such as wetlands or drainage systems to prevent flooding in certain areas
How do Green Roofs improve Drainage?
They allow for infiltration on top of previously impermeable rooftops and prevents leakages and damage to the roofs of apartment blocks and offices
How do Tree Pits improve Drainage?
They are areas that have been reformed to include infiltration on pavements or separating two sides of a road, it allows for more infiltration in these areas where drainage systems would normally feel stress under heavy rain
How do Permeable Pavements improve Drainage?
These new pavements are designed to store and infiltrate water through semi permeable rocks that can still be used as a pavement. They contain storage containers underneath that releases water at safe discharges into drainage systems
