Lesson 19-Urban Drainage Flashcards
Urban drainage
- Built up areas need to be drained to remove surface water run-off. Traditionally been acheived by using underground pipe systems to transfer the water away as quickly as possible
- not designed for attractiveness
- poor water quality issue
- modern approaches offer a more holistic approach
What factors casue rain water to stay on the surface in urban areas?
- Impermeable surfaces like roads, carparks and rooftops all prevent precipitaion from infiltrating the ground
Outline features of urban areas which are designed to shed water quickly
Sloping roofs,smooth and rounded guttering and cambered roads all contribute to the rapid movement of water away from the surface
What is a ‘flashy’ hydrograph
Short lag time between the rainfall amount and discharge. Increases the risk of the hazard as it occurs much faster
Why are many more people now at risk from flooding?
- Population and urban growth
- Predicted increase in occurance of servere weather as a result of climate change
How and why are people in Asia going to be at risk of more flooding?
- Sinking under their own weight and effects of groundwater extraction by their residents
- In parts of Kakarta, a city with 9.6 million people, the ground has shrank by 2.5 metres in less than a year
CASE STUDY SUSTAINABLE RIVERS- River Don, Sheffield
- Industrial waste thrown in river-resulting in acid rain
-heavy metals
-paints and dyes - Feacal matter from animals
Why were rivers historically polluted?
- Industry formed around rivers as they were the moterways of the era
- Rivers had mercury, lead and other metals from growing industry located near these rivers
What in the upper-course may impact flooding in Sheffield?
- Deforestation
- Agriculture-paralell ploughing to the river will prevent river flooding as it wont funnel the water to the river
- Intense grazing may mean water wont be abosrbed as the soil wont be fertile
- Decline of species like beavers who microengineer tributaries
URBAN DRAINAGE CASE STUDY- The Five Weirs Walk, Sheffield
- Spans from the city centre to Meadowhall
- Previously the most polluted river in the UK
- Deindustrialisation occured, deprivation, pollution,crime>vandalism and grafiti making the walk unpleasant
How was the Five Weirs Walk regenerated?
- Concrete and walled river reinforcements, river banks regenrated, cleared the river channel of debris and waste> lowered the river level
What were the impacts of the regerenation?
- Reduced risk of flooding as river capacity is higher
- River ecosystem is regenerating>trees and mammal species
How the regeneration was socially, economically and environmentally stable?
- Social-improves mental health due to air quality and sense of place
- Economic-reduces impact of flooding, attracts people to the area
- Environmental-improves air quality
Negatives of the Five Weirs Walk regeneration
- The use of flood defences like dredging, in Sheffield has been linked to increased flood risk further down the course of the River Don. 2019 floods near Doncaster were blamed on this
- Flood risk is still a huge concern for Sheffield
- Recent flood damage of Five Weirs Walk is yet to be fixed
CONTRASTING CASE STUDY OF SUSTAINABLE RIVERS-Cheonggyecheon, South Korea
- The overpass negatively affected the competitiveness of thousands of buisinesses
- Elavated the freeway and concrete deck covering the stream were dismanteled
- 22 bridges, 12 pedestrian pridgesa and 10 for cars were built to improve movement across north-south
