Win 2016: The Hydrological Cycle Flashcards
How can you modify this diagram (water cycle diagram) to slow down the movement of water to the ocean?
Grow more trees. This will reduce the speed of surface water run off and the roots will trap more water. It may also help to change from coniferous to deciduous trees as when they are in leaf they intercept the rain more effectively. Dig ditches in the land to slow the water down.
How will a warmer climate alter the hydrological cycle?
If the air temperature is warmer, the sea will warm too. This will cause more evaporation to occur and this will lead to more precipitation on land. A warmer climate will also lead to melting of snow and glaciers. As a result rivers and streams will flood more easily and the sea level will rise.
Explain how a flood (river or coastal) you have studied was caused.
16 August 2004 flash flood occurred at the confluence of the River Jordan and Valency near Boscastle in Cornwall. Boscastle is situated at the end of a narrow valley with interlocking spurs. the steep valley encouraged rapid surface run off. Soil in the valley is made up of impermeable clay. 185 mm of rain had fallen in 5 hours. The soil was saturated and the impermeability of the soil meant it could not infiltrate easily. The rain was caused by the meeting of 2 air masses. One coming from the south. The other from the south west. This lead to towering cumulonimbus clouds up to 10 km high. The natural channel of the river had been walled to made a pedestrian area which prevented it from adjusting its channel. The village was built on the flat flood plain. Cars trees and boulder became stuck under a bridge causing a build up of water behind it. The force of the water eventually washed away the bridge and roads were submerged under 2.75 m of water. 4 buildings are demolished and 58 flooded. The Museum of Witchcraft lost 50% of its artifacts. 90% of the income in Boscastle is based on tourism and there were still 3 weeks of holiday left. Luckily no one died. Emergency worker rescued residents and holiday makers from a 32km stretch of the north Cornwall coast. It was a well co-ordinated and well resourced rescue plan. Seven helicopters from the Coastguard, Royal Navy and RAF were used. The Environment Agency carried out an investigation after the flood. A grant of £2m was given to help prevent more floods. No schools or old people’s homes can now be built in the valley. The Boscastle flood was caused by physical, climatic and human factors acting in combination. The valley shape, usually heavy rains and the dam caused by the bridge all contributed to this very serious flood.
