Sediment river loading rates

Rivers transport suspended sediments derived from the disintegration of basin surface layers. With reduced velocity, sediment is deposited in the river channel. The finest material is carried to the sea. It has been estimated that the average mechanical denudation rate for continents is 0.056 mm year (35). This is based on a total suspended load of 13.5 x 10 metric tons year (S). Presently, about two-thirds of the world s total suspended sediment load derives from Southern Asia and large Pacific Islands. Berner has estimated the increase in sediment loss in the U.S. and world since prehuman times to be approximately 200% (35). Current estimated erosion rate from the major land forms is provided in Table I. The relatively recent construction of large sediment trapping dams that normally caused sediment to be deposited in river valleys or transported to the ocean has drastically reduced sediment yields in great rivers. 

River transport of clay minerals into the ocean is spatially and temporally variable. The global annual suspended load of river sediment into coastal waters currently averages 12.6 X 10 ton. This flux is approximately 10% less than was delivered before humans began damming rivers. (One notable exception is the Mississippi River, whose sediment load has increased due to very high rates of soil erosion. The riverine sediments deposited in the mouth of the Mississippi River form one of the world s largest deltas.)... 

River water runoff is responsible for many hydrological features of river mouths and their parts - deltas, semi-enclosed coastal water bodies and open nearshore zone. Water runoff influences water levels in deltas, delta inundation, water salinity at the mouths, etc. Water runoff depresses action of the storm surges on the deltas. River sediments load determines channel processes, sedimentation in a delta and nearshore, delta formation processes, the rate of delta progradation into the sea. 

Over the above-mentioned period, average value of the deposition of riverine sediments in the delta and liman was equal to 2.3 x 1061 year-1 or close to one-half of the river sediment load [12]. Thickness of layer of deposition during the same period comprised 0.55 m [12], and average rate of accumulation exceeded 0.3 mm year-1. 

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