AQA A-Level Geography 7037
Water and Carbon Cycles
Hot Desert Systems and LandscapesLandscape
Coastal Systems and LandscapesLandscape
Glacial Systems and LandscapesLandscape
HazardsHazards or ecosystems
Ecosystems Under StressHazards or ecosystems
Global Systems and Global Governance
Changing Places
Contemporary Urban EnvironmentsHuman option
Population and the EnvironmentHuman option
Resource SecurityHuman option
Contemporary Urban Environments
Urban Hydrographs
- 3 things to know
- Component 2
Overview
Recall questions on shorter lag times, higher peak discharge, steeper rising limbs and the flashy response of an urban catchment.
What you need to know
Answer each one before you reveal it.
What causes urban hydrographs to show flashier responses with quicker return to base flow?
What is combined sewer overflow pollution?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Why do urban hydrographs typically show shorter lag times than rural catchments?
Model answer
Water is transferred rapidly across impermeable surfaces to efficient drainage systems, reducing the time between peak rainfall and peak discharge.
- 2
Explain why urban hydrographs display higher peak discharge than rural equivalents.
Model answer
Reduced infiltration and storage means a greater proportion of rainfall becomes surface runoff, and this water reaches channels quickly, concentrating flow into a higher peak.
- 3
Why do urban hydrographs have steeper rising limbs?
Model answer
Efficient artificial drainage networks channel runoff rapidly to rivers, causing discharge to increase quickly after rainfall begins.
- 4
What causes urban hydrographs to show flashier responses with quicker return to base flow?
Model answer
Limited groundwater recharge means there is less sustained throughflow contribution to maintain river levels, so discharge falls rapidly after the storm peak.
- 5
How does urbanisation increase flood risk?
Model answer
Rapid runoff from impermeable surfaces, reduced storage and efficient drainage concentrate water quickly, increasing peak flows that can exceed channel capacity.
- 6
What is combined sewer overflow pollution?
Model answer
During heavy rainfall, combined sewers carrying both stormwater and sewage can overflow, discharging untreated sewage and pollutants directly into rivers.
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