Rivers & Coasts Case Studies

Landform features: Chalk & glacial till cliff; wave cut platform; caves, arches & stacks; bays and healands. The Cliffs in Selwicks Bay: The rocks of the chalk cliff are erodes by the waves at sea level. Erosion will be abrasion and hydraulic action. The waves cut a wave cut notch in the bottom of the cliff, gets bigger and cliff develops an overhang, eventually cliff above collapses. Collapsed rocks collect at base of cliff. These rocks get broken up and rounded by attrition. Cliff recession; the cliff moves backwards over hundreds of years and leaves a platform at wave level called a wave cut platform, can be seen at low tide. Glacial till above chalk is very soft and forms a more gentle cliff. Sometimes till gets saturated and huge sections move downslope and fall over the chalk cliff to the wave cut platform below. Selwicks Bay and Headlands: Selwicks bay formed because the rocks of the Bay area eroded faster than the rocks making the headlands either side. There is a big fault line that runs right down the middle of Selwicks Bay, makes the rock weaker here. The sea was more easily able to erode along this fault line weakness that the rock areas either side. This formed a bay and left the rock either side as headlands. Caves, Arches & Stacks in Selwicks Bay: Fault lines in the chalk cliff are eroded more easily than the surrounding rock. Erosion from abrasion has widened the faults into caves. If the waves erode the cave through to the other side of a cliff the an arch is formed. When the arch collapses it will leave a stack.

The Landform Features: Upper Course; High Force Waterfall; V-shaped valley Middle Course; Meanders. How did High Force Waterfall form? Hard rock lay on top of softer rock. As the river passes over the more resistant hard rock it erodes slowly(abrasion & hydraulic action). The softer rock below is eroded more quickly, this creates an overhang as the erosion gradually undercuts the hard rock. A plunge pool forms at the base of the waterfall-due to erosion as the force of the water hits the soft rock below it churns round the rocks broken off from above and rubs them against the river bed. Eventually the undercut becomes so large the hard rock collapses into the plunge pool, deepening it, and the waterfall retreats upstream to form a recession gorge. The Formation of the Upper Teesdale V-shaped Valley: Erosion is main force in upland areas- more energy. Vertical or downwards erosion deepens river valley; lateral or sideways erosion widens valley. Weathering breaks up rock on slops and slope processes take weathered material to river. Helps lower valley sides making them gentler. In upland areas the downwards erosion of the river is faster than sideways erosion or weathering & slope processes on the side. Cannot keep up with fast downwards erosion; this means a steep, v-shaped valley is formed. The interlocking spurs are formed as the river winds round and cuts into the valley sides. Formation of River Tees Meanders: Erodes laterally or sideways, widens the river makes a flat valley floor(flood plain). The fastest more powerful current goes to the outside of the meander bend, erodes the outside of the meander bend forming a steep river cliff. Inside current is slower, river loses energy and drops material it is carrying- slip off slope.

Physical Causes of Flooded: Impermeable rock of Bodmin Moor, Soils already soaked, Very intense rainfall, steep slopes. Human Causes of Flooding: Location, Vegetation removal, Altered channel, Low bridges, Tree planting. Impacts of the flood on People & Environment: Main street turned into a river . 116 cars were picked up by the river and taken out to sea. Road bridge got blocked with debris and eventually collapsed. 4 footbridges collapsed. 50 buildings were flooded, 4 of which were demolished. Contents of shops and houses were washed away. 25 business properties destroyed. Visitor centre destroyed. Insurance companies paid out an estimated £20 million to repair damaged property. When floodwaters went down thousands of tonnes of mud and debris were left thoughout the lower part of village. Tourism (90% of income) badly affected. Local businesses lost money. Measures to deal with Impact: Short Term; People had to be airlifted to safety by RAF. People were taken to temporary shelter and emergency food and water was supplied. Bulidings had to be dried out using large heaters and fans. Long Term; Lots of rebuilding took place. £1 million has been spent on a new flood defence system. The culvert has been widened and can carry twice the amount of water. River bed has been lowered to make river channel large. Wider span bridge has been built so it doesn't become blocked with debris. Flood defence walls have been constructed, making the capacity of the river greater. Car park raised. More trees have been planted in the catchment area- more infiltration, less overland flow.

Physical Causes: 80% of Bangladesh is a huge flood plain. Flat & low-lying. Has a monsoon climate, over 80% of total annual rainfall happens in 4 months. Rivers flood naturally, this is beneficial as it provides water for rice crops. Coincides with high temperatures- melts snow and glaciers in th Himalayas. Human Causes: Deforestation, River diversion, International Loans, Inadequate Aid. Impacts of 1998 floods on People & Environment: 70% of country flooded for over 70 days. Water in Dhaka was 2 metres deep & covered 3/4 of city. Electricity supply cut off. Wells were flooded, water in them polluted. 7 million homes were destroyed. Over 25 million made homeless. Death toll was over 1300. Most deaths due to drowning but others suffered from diseases. 2 million tonnes of rice was destroyed. Most of the jute, sagar cane ans veg crops were lost. Half a million cattle and poultry died. Thousands of kilometers of roads, a third of the railways and Dhaka's ariport were flooded. Impossible to deliver food and medical help to those in need. 400 factories closed leaving 166,000 works jobless. Over 4000 schools destroyed. Measures: Short Term; WHO supplied medicine and water purification tablets. International aid allowed government buy 350,000 tonnes cereal crops from Asian countries for food. Long Term; Impossible to prevent flooding in Bangladesh. In 1989, the government began working on a Flood Action Plan to minimise flood damage and maximise flood benefits. This included; 5000 flood shelters in areas most at risk. Improve the forecasting system. Build dams to control river flow and hold back the monsoon rainwater in resevoirs. Drain the area before the monsoon rains.