From the Blog

An aerial picture of Poole Harbor’s flooded ria.

As well as rivers having an important role around the world in terms of their interactions with man they have also produced a number of spectacular landforms. These have either been formed by the river eroded away land or rivers depositing its material to form new lands. The river generally erodes more when it is closer to its source and is flowing in upland areas. One of the most common features a river forms is a V shaped valley. Water always heads naturally downwards with gravity, so when it is the high as well as flowing forwards it is also scouring downwards into its bed. This results in a V shaped valley as natural weathering processes will erode back the sides of the valley. One of the best examples of a V shaped valley is in Reggio Calabria in Italy where the Amendolea River has meandered down the valley eroding out a perfect V shape with the land in between the meanders known as interlocking spurs. When V shaped valleys reach coasts they are sometimes drowned by rising sea levels. This results in large inlets being left behind, and they are often great locations for harbors. Poole harbor in the UK is the second largest natural port in the world, and was formed when the valleys of several local rivers were flooded at the end of the last ice age.

The Jollie River U shaped valley

Such perfect shapes in upland areas are relatively rare as many of these areas have also been subjected to glacial processes. Glaciers have followed the rivers and have scoured out the sides of the valleys to leave perfect U shaped valleys. The Jollie River in New Zealand’s Southern Alps flows down a valley that in time has been shaped by a previous glacier. This has left behind a pronounced U shaped valley that is occupied by the River Jollie. When U shaped valleys reach the coast rising sea levels will often leave behind huge deep flooded areas which are known as Fjords or Lochs. One of the famous lochs in the world is Loch Ness which is located in the Scottish Highlands just to the South-West of Inverness. The lake is 37km long and in places it is 230 meters deep. As rivers flow towards the sea they will often meander as they follow changes in the gradient of the land. Sometimes the meanders become so pronounced that in times of great flow the water will break across the meander leaving behind an ox bow lake.

In Sussex the Cuckmere River has a series of small ox bow lakes where the river enters the English Channel. This area is known as Cuckmere Haven and these floodplains are found between Eastbourne and Seaford. Floodplains themselves are major geographical landforms that are found in the lower reaches of a river. They are formed when a river regularly breaks it bas bank during times of high discharge flooding the surrounding land. The waters drop rich silt which is a rich agricultural product for the local populations. This can lead to government’s having a major quandary. On the one hand they want to protect their citizens from drowning but they also kno3w that by stopping the river from flooding will starve the soils of vital nutrients. Similar deposits are found at the ends of rivers as they enter lakes or seas and they are known as delta. At the end of its journey the river is transporting a lot of material but on hitting a wall of water the velocity drops and the silt is merely dropped to form deltas. The largest delta in the world is the Brahmaputra and Ganges delta. The fan shaped feature measures 354 km across and the whole of Bangladesh virtually all lies on the delta. With the delta people are in danger from both the rivers flooding plus storm surges sending rising sea levels up the Bay of Bengal to overcome sea defenses.

Rivers have produced many features tha are found in the world today.