Planning new sites for dam construction involves research about the impacts on the ecosystem such as the interruption of fish migration, however sediment contamination is given less importance (Wildi, 2004). Sediment contamination in the reservoir area is extremely important because it involve several environmental risks.

The dam construction decelerate the river flow making the reservoir upstream a trap for suspended sediments. The fine grained particles settle down to form fine grained sedimentary deposits that are highly contaminated by organic pollutants and toxic heavy metals if there is  industrial urban areas or agricultural areas upstream the dam (Sedláček, 2013).                     

These deposits impose a serious environmental hazard due to risk of remobilization of heavy metals and the other contaminants back to the environment.

The are different processes of remobilization. Probably most dangerous is erosion of the contaminated deposits and resuspension of contaminants due to changes in the hydraulic regime. This could happen because of several reasons like dam failure, removal of old dams, changes of the reservoir storage, flooding in which resuspended contaminant could be transported beyond the the limits of the reservoir and infiltrate groundwater.

Further fine grained sediments deposits has high water content and are very unstable therefore can be affected by gravity processes such as landslides(Wildi, 2004).

Also the uptake of contaminants (principally the metals) from the sediments by aquatic organisms and plants is an important ecological issue because the contaminants pass to higher consumers through the food webs (Wildi, 2004).

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