Rivers

Rivers

1. Erosion

   • Erosion is the wearing away of land surface by natural agents; water, ice and wind.The transporation of rock debris and features produced and deposited.
   • Rivers are flowing bodies of water. There are rivers on every continent(ecept antartica).Rivers are an importantpart of Earth's water cycleand the sculpting of the Earth's topography as they carry huge quantities of water deom the land to the sea.

2. The Lower Course Of A River

   • The Sea
   • The lower course has the gentelest slopes - both long in profile and across the valley floor. In the lower course the river has a high volume and a large discharge. However, as a river reaches the end of it's journey, energy levels are low and deposition takes place.
   • The river now has awide flat land known as floodplain. A floodplain is the area around a river that is covered in times of alluvium on the banksof a rivercan create levees, which raise the river bank. The river may have large meanders and oox-bow lakes. The mouth of a river is when it reachesopen water - either a lake or the sea. Under certain conditions a delta ican ne found here.
   • In the lower course the meanders become even larger. Erosion on the outside of bends and deposition on the slip off slopes continue to take place. The erosion causes the meander neck to narrow until eventually it breaks through. This often takes plce when the river has more energy as in time of flood.
   • Deltas
     • Some rivers reach the sea in deltas, which from where river mouths become chocked with sediment, causing the main river channel to split into hundreds of smaller channels of distributies.

3. The Midle Course Of A River

   • In the middle course the angle that the river flows down is less steep, the river begins to meander and the vally sides are also less steep. In the middle cours the river has more energy and a high volume of water. The river channel has also deepened. A larger river channel means there is less friction, so the water flows faster.
   • As the river erodes laterally, to the right side then the left side, it forms largerbends, and then horseshoe-like loops called meanders. The formationof meanders is due to both depostion and erosion and meanders gradually migratedownstream.

4. The Upper Course Of A River

   • As the river moves through the upper course it cuts downwards. The gradient here is steep and the river channel is narrow. Vertical erosion in this highland part of the river helps to create steep sided V-shaped valleys, inter clocking spurs, rapids, waterfalls and gorges.
   • The upper course is the highest section which is found in the moutains or hills. Herethe river erods a V-shaded valley, the path is straight and it flows downhill steeply. The landforms that are common in this course of the river are waterfalls and gorges.
   • The Formation Of A Waterfall
     • Water passes over hard rock and erodes the softer rock below. A plunge pool is formed and the river erodes backward as the water and rock swirl around. Eventually the hard cap rock overhangs and collapses under gravity. This process continues over time and the waterfall moves backwards or reaches to form a gorge.

5. River Flooding

   • Floodingis a completly natural process - it can only cause problems to people when people have built on river flood plains.
   • Causes Of Flooding
     • Deforsestation
     • Snow melts
     • Precipitation
     • Flash flood
     • Urbanistation

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