1800775
Description
Flashcards by ellierosedyson, updated more than 1 year ago
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Created by ellierosedyson
over 9 years ago
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| Question | Answer |
| Name three characteristics of a river channel/valley? | 1) oxbow lake 2) meander 3) floodplain |
| explain how oxbow lakes are formed? | 1) River meanders along the valley eroding laterally. 2) Erosion occurs on the outside of the bend and deposition occurs on the inside of the bend. 3) Meander neck is narrowed by erosion + river leaves the meander continuing through the new bed. 4) New deposition seals off its ends and the cut off becomes an oxbow lake. |
| Why does deforestation link to flooding? | Removing trees reduces the amount of water intercepted and increases run-off |
| EXPLAIN a reason for flooding | if two rivers reach peak discharge at the exact same time this can cause river flooding. |
| EXPLAIN how impermeable surfaces can cause flooding? | In urban areas there are more impermeable surfaces (e.g.: concrete) these surfaces increase run off which can cause river flooding. |
| why soft engineering is better than hard engineering? | -less expensive -Sustainable -long term -environmentally friendly |
| Describe three strategies used in soft engineering? | Afforestation: Planting trees near a river so there is greater interception of rainwater and lower river discharge Ecological flooding: River allowed to flood naturally in places to prevent flooding in other areas. planning: local authorities introduce policies which control urban development on a floodplain or near it. |
| Why is hard engineering not as good as soft engineering? | Hard engineering is more expensive and has a greater impact on the river and surrounding landscape. |
| What is a levee? | A levee is an embankment built to prevent the overflow of a river. |
| How does the shape of a river valley change downstream? | Size and shape the valley changes down stream. goes from steep v-shaped valley to a broad almost flat v-shaped valley. |
| Explain formation of a levee? | 1. River carrying sediment overflows its banks and course material is dropped. 2.this material forms a natural embankment along the edge of the river channel. 3)frequent flooding can cause the levee's to become naturally higher |
| What is river flooding? | River flooding is when a river bursts its banks and water spills onto the floodplain. Tending to be caused by heavy rainfall. |
| Describe one physical cause of flooding? | if a channel is steep sided it is surrounded by steep slopes which causes fast surface run off. |
| Define lag time? | Lag time is the time taken between peak rainfall in a basin and peak discharge in the river. It is how long it takes for rain to get into a river. |
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