What are some causes of flooding?
- Steep slopes which increases surface runoff
- Building on floodplains (with impermeable materials)
- Impermeable rocks and soils
What are soft engineering strategies?
Strategies that work with natural processes to reduce flooding
What are hard engineering strategies?
Strategies that involve building artificial structures to reduce flooding
What are examples of soft engineering strategies?
- Flood warnings
- Floodplain zoning
What are examples of hard engineering strategies?
- Dams
- River straightening
- Embankments/flood walls
- Flood relief channels
How are floods managed in Boscastle?
- River widened/deepened so has a larger capacity
- Flood defence wall so more drainage
What are V-shaped valleys?
(Formed by erosion)
- Caused by vertical erosion
- Valleys are eroded by hydraulic action and abrasion
- Steep-sided valleys
What are interlocking spurs?
(Formed by erosion)
- Upper course (river doesn’t have enough energy for lateral erosion)
- River follows the path of least resistance
- Hills form on either side of the river and the river flows around the hills
How are waterfalls formed?
(Formed by erosion)
- Soft rock is easier to erode (abrasion + h.a)
- Hard rock is resistance so a ledge forms
- Water flows over ledge and erodes soft rock, forming a plunge pool
- Ledge collapses into plunge pool, debris speeds up erosion
- This repeats as waterfall retreats, forming a gorge
How are meanders formed?
- More erosion on outside bend (faster flow), forming river cliffs
- More deposition on inside bend (slower flow), forming slip-off-slope
What is thalweg?
The line of deepest water and fastest flow in a river channel
How are oxbow lakes formed?
- The neck of the meander eventually becomes closer together (river erodes more, bringing bends closer)
- Meander joins in the middle
- Water follows straightest path so meander closes and oxbow lake forms
How are floodplains formed?
(Formed by deposition)
- Flat land next to a river in middle/lower course
- This area floods when river’s water level rises
- Made from layers of sediment (silts, sands and clays) deposited by the river when it loses energy
How are levees formed?
(Formed by deposition)
- Formed by coarse material which builds up at river banks
- Not all rivers can form levees
What are estuaries?
A wide body of water where the river meets the sea
