Factors affecting the risk of flooding Flashcards
(16 cards)
What is bankfull capacity?
The maximum amount of water that a river channel can hold before it overflows its banks.
Influenced by the channel’s shape, size, and the surrounding landscape.
What effect does intense or prolonged rainfall have on flood risk?
Can saturate the ground, leading to increased surface runoff.
Heavy, short-duration rainfall creates a flashy hydrograph due to rapid runoff.
How does prolonged, steady rainfall affect hydrographs?
Leads to a subdued hydrograph as water infiltrates the soil before reaching the river.
What type of rocks prevent infiltration?
Impermeable rocks (e.g., clay, granite).
They lead to more surface runoff.
What is the impact of impermeable surfaces on hydrographs?
Creates a flashy hydrograph due to quick runoff.
Which type of rocks allow infiltration?
Permeable rocks (e.g., sandstone, chalk).
They lead to a subdued hydrograph.
How does soil type affect flood risk?
Soil permeability affects water absorption; sandy soils absorb more water than clay soils.
What is the effect of steep slopes on water flow?
Cause rapid runoff as it’s easier for water to run over the land than infiltrate the soil (flashy hydrograph).
How do gentle slopes influence water movement?
Water moves more slowly, leading to a subdued hydrograph.
How does drainage basin shape affect water flow?
Circular basins concentrate water flow quickly (flashy hydrograph), while elongated basins spread water flow over a longer period (subdued hydrograph).
What is the effect of urbanization on flood risk?
Increases surface runoff due to impermeable surfaces (e.g., concrete, tarmac).
Urban areas create a flashy hydrograph due to rapid runoff.
How does deforestation affect flood risk?
Reduces interception and increases surface runoff.
Deforested areas create a flashy hydrograph due to increased runoff.
What farming methods can affect flood risk?
Ploughing and crop rotation.
Poor agricultural practices create a flashy hydrograph due to increased runoff.
How do drainage systems influence flood risk?
Efficient drainage systems can quickly channel water away from urban areas but may increase flood risk downstream.
What is the result of well-maintained drainage systems?
Can create a flashy hydrograph due to rapid water movement.
What might poorly maintained drainage systems lead to?
May lead to a subdued hydrograph as water is retained longer.
