Deltas and Distributaries
A delta is a low lying landform that occurs near the mouth of a sediment carrying river, near the ocean/ a lake or another river that is unable to remove the sediment as fast as it is deposited. They are commonly home to very fertile soil, large amounts of vegetation and attract lots of birds, wildlife and fish (About.com, 2014). Deltas form over a long period of time, transporting particles of sand, silt, mud, and gravel down their course to be deposited at the mouth. As sediment continues to be deposited the water level grows more shallow and eventually the delta rises above the water level (Stone, 1974). As the remaining water still needs to get out to the ocean; the most powerful flowing water may occasionally cut across the land and form distributaries giving the typical fan shape that deltas are known for (About.com, 2014).
The formation of deltas has been illustrated by C, R, Stone in his book: Australian Landforms. each image is spaced several hundred years apart and shows the development of deltas, distributaries, and lagoons.
The formation of deltas has been illustrated by C, R, Stone in his book: Australian Landforms. each image is spaced several hundred years apart and shows the development of deltas, distributaries, and lagoons.
There are 3 main types of delta, each classified based on what causes the river to deposit its sediment:
Wave-Dominated deltas is where wave erosion control how much sediment remains after the river dumps it. Areas with large wave activity will not often form deltas as all the sediment is washed out to sea.
A tide-dominated delta may form based on the height and strength of the tide during times of high water. As the tide recedes it takes some sediment with it, if the tidal forces are stronger with a high tidal variation (very high and very low tides) it will remove more sediment and instead of a delta, a estuarie will form.
Inland Deltas are steeper than traditional deltas and deposit coarser material. They generally form in dried lake beds, fanning out and inter-cut with distributaries then rejoining further downstream (About.com, 2014).
Wave-Dominated deltas is where wave erosion control how much sediment remains after the river dumps it. Areas with large wave activity will not often form deltas as all the sediment is washed out to sea.
A tide-dominated delta may form based on the height and strength of the tide during times of high water. As the tide recedes it takes some sediment with it, if the tidal forces are stronger with a high tidal variation (very high and very low tides) it will remove more sediment and instead of a delta, a estuarie will form.
Inland Deltas are steeper than traditional deltas and deposit coarser material. They generally form in dried lake beds, fanning out and inter-cut with distributaries then rejoining further downstream (About.com, 2014).