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Impacts of sediment retention by dams on delta shoreline recession: evidences from the Krishna and Godavari deltas, India
Author(s) -
Rao K. Nageswara,
Subraelu P.,
Kumar K.Ch.V. Naga,
Demudu G.,
Malini B. Hema,
Rajawat A.S.
Publication year - 2010
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.1977
Subject(s) - delta , river delta , sediment , geology , hydrology (agriculture) , shore , erosion , structural basin , oceanography , dominance (genetics) , progradation , physical geography , geography , geomorphology , sedimentary depositional environment , biochemistry , chemistry , geotechnical engineering , aerospace engineering , engineering , gene
River deltas are the major repositories of terrestrial sediment flux into the world's oceans. Reduction in riverine inputs into the deltas due to upstream damming might lead to a relative dominance of waves, tides and currents that are especially exacerbated by coastal subsidence and sea‐level rise ultimately affecting the delta environment. Analysis of multi‐date satellite imagery and maps covering the Krishna and Godavari deltas along the east coast of India revealed a net erosion of 76 km 2 area along the entire 336‐km‐long twin delta coast during the past 43 years (1965–2008) with a progressively increasing rate from 1·39 km 2 yr −1 between 1965 and 1990, to 2·32 km 2 yr −1 during 1990–2000 and more or less sustained at 2·25 km 2 yr −1 during 2000–2008. At present the Krishna has almost become a closed basin with decreased water discharges into the delta from 61·88 km 3 during 1951–1959 to 11·82 km 3 by 2000–2008; and the suspended sediment loads from 9 million tons during 1966–1969 to as low as 0·4 million tons by 2000–2005. In the case of the Godavari delta, although the water discharge data do not show any major change, there was almost a three‐fold reduction in its suspended sediment loads from 150·2 million tons during 1970–1979 to 57·2 million tons by 2000–2006. A comparison of data on annual sediment loads recorded along the Krishna and Godavari Rivers showed consistently lower sediment quantities at the locations downstream of dams than at their upstream counterparts. Reports based on bathymetric surveys revealed considerable reduction in the storage capacities of reservoirs behind such dams. Apparently sediment retention at the dams is the main reason for the pronounced coastal erosion along the Krishna and Godavari deltas during the past four decades, which is coeval to the hectic dam construction activity in these river basins. Copyright © 2010 John Wiley and Sons, Ltd.