However, the barrage could have a compensating impact on the level of silt and sediment suspended in the water. The waters of most estuaries carry much silt in suspension, churned up by the tides, making the water impenetrable to sunlight. With the barrage in place the reduced flows would enable the silt to drop out, making the water clearer. Given this change in 'turbidity', sunlight would penetrate further down, increasing the biological productivity of the water and thus increasing the potential food supplies for fish and birds. The net impact for the ecological balance might therefore be positive.
Erosion is usually a major problem in the areas suitable for tidal power.
Also, the muddy areas of the estuaries generally do not provide suitable foundations for barrages. Foreign materials such as mullock and mine waste rock has to be added both to the estuary banks and the foundations of the barrage. Although this means a greater capital cost it does provide the benefit of flood and storm damage protection. Acid sulfate soils, if it resides at the site, presents a major concern. The disturbance of these soils has the potential to cause a major influx of acidity of the estuary in question which will largely impact on the ecological system of the estuary.