Sediment yield

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. 

Figure 4. Discharge of suspended sediment from world rivers in 10 tons ear. Sediment yield in tons/km ear for major drainage basins is shown by pattern (see key).

The sediment load of a channel and the sediment yield of its drainage basin are expressed in different ways. The sediment load is the total mass of material moved by the river in a... 

F g- 8-9 Generalized variation of sediment yield with precipitation. (Modified from Langbein and... 

Fig. 8-11 Annual sediment yield for various land uses in northern Mississippi vs. annual precipitation. (After Ursic and Dendy, 1965.)...

Church, M. and Slaymaker, O. (1989). Disequilibrium of Holocene sediment yield in glaciated British Columbia. Nature 337,452 54. 

Dunne, T. (1979). Sediment yield and land use in tropical catchments. /. Hydrol. 42, 281-300. 

Hallet, B., Hunter, L., and Bogen, J. (1996). Rates of erosion and sediment yield by glaciers A review of... 

Ursic, S. J. and Dendy, F. E. (1965). Sediment yields from small watersheds under various land uses and forest covers. Proceedings, Federal Inter-Agency Sedimentation Conference 1963. US Dept, of Agriculture Misc. Publ. 970,47-52. 

Earth (Li, 1976). The high denudation rate is a reflection of the poorly lithifled, highly tecton-ized nature of the sedimentary rocks that compose the island. Sediment-yield data compiled by Milliman and Meade (1983) and Milliman and Syvitski (1992) indicate that island arcs and mountain belts in the tropical and subtropical west Pacific may contribute as more than 22% of all solid material discharged by rivers into the ocean. Furthermore, the tropical mountainous areas in southeast Asia and India may contribute another 33%. 

Tarras-Wahlberg NH, Lane SN (2003) Suspended sediment yield and metal contamination in a river catchment affected by El Nino events and gold mining activities the Puyango river basin, southern Ecuador. Hydrol Process 17 3101... 

Wright SA, Schoellhamer DH (2004) Trends in the sediment yield of the Sacramento River, California, 1957-2001. San Francisco Estuary Watershed Sci 2(2) Article 2. http // repositories.cdlib.org/Jmie/sfews... 

Plater et al. (1988) developed a similar approach to estimate mean sediment yield... 

The Agricultural Runoff Management (ARM) Model, developed by Hydrocomp Inc. for the U.S.EPA (2 ). It simulates the hydrology, sediment yield, and nutrient and pesticide behavior of the land phase of the hydrological cycle. The same organizations also developed the Non-Point Source (NPS) Model (3) which handles the washoff of miscellaneous pollutants from land surfaces. 

Table I Summary of sediment yield estimations in the lower River Ebro (modified from [55])...

This chapter has summarised the main hydrological and sediment transport trends observed in the Ebro basin during the twentieth century. Most data concentrates in the lower reach of the catchment and in recent years and, therefore, this area has driven most of the attention of the work. The Ebro flow and sedimentary regimes are profoundly marked by the human action in the entire basin. Changes in land uses and especially dam construction have change the historical pattern of water and sediment yield, and the associated physical processes (i.e. riverchannel sedimentary structure and morphology). 

Batalla RJ, Vericat D (2010) An appraisal of the contemporary sediment yield in the Ebro basin. J Soils Sediments (in revision)... 

Walling DE (1984) Dissolved loads and their measurements. In Hadley RF, Walling DE (eds) Erosion and sediment yield some methods of measurements and modeling. Geo Books, London, 111-177... 

Walling DE, Webb BW (1983) Patterns of sediment yield. In Gregory KJ (ed) Background to Paleohydrology. Wiley, Chichester, pp 69-100... 

Walling DE, Webb BW (1996) Erosion and sediment yield a global overview. Proceedings of the IAHS symposium on erosion and sediment yield global and regional perspectives, vol 236. IAHS Red Book, Exeter, pp 3-19... 

McDowell, L.L., G.H. Willis, C.E. Murphree, L.M. Southwick, and S. Smith. 1981. Toxaphene and sediment yields in runoff from a Mississippi Delta watershed. Jour. Environ. Qual. 10 168-173. 

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