Dams change river topography mainly by trapping sediment and causing silting, which alters both upstream and downstream landscapes��.Upstream EffectsWhen a dam is built, the river slows down as it enters the reservoir, causing sediments like silt, sand, and gravel to deposit and accumulate�. Over time, this reduces reservoir capacity and raises the riverbed profile upstream of the dam�.Downstream EffectsDownstream, sediments are trapped by the dam, so the river is starved of its natural load. This leads to:Riverbed erosion and channel incision, making the riverbed deeper and steeper��.Loss of fertile silt for floodplains, impacting agriculture and riparian habitats��.Coarsening of the riverbed, with less fine sediment and more gravel and cobbles��.Geographical ImpactLong-term silting behind dams reshapes floodplains, cuts off deltas from sediment supply, and changes habitats for plants and aquatic life along the river���. Coastal erosion also intensifies where rivers can no longer deliver sediment to maintain beaches and deltas��.In summary: Dams interrupt the natural sediment journey, which causes siltation upstream and erosion plus ecological change downstream
#topography #upstream #downstream
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