This page provides information on dredging and its effects on our watershed.
On this page we cover:
-What is dredging?
-Is dredging a good solution for flood mitigation?
-What are the effects of dredging on our river and stream systems?
Unintended Effects of Dredging
Dredging often comes with unintended consequences. This simplified demonstration shows how dredging a river channel can have catastrophic effects both upstream and downstream.
Key takeaways from video:
1. Dredging can cause increased water flow that the water system is not designed to handle
2. Dredging can cause erosion of banks due to increased flow
3. Dredging disrupts natural ecosystems and processes
Click the titles to view the full articles
"Dredging is not a universal solution to flooding. Numerous studies dating back to the 1980’s have shown that dredging can speed up flow and potentially increase the risk of flooding downstream and have devastating unintended consequences for wildlife and people’s homes and businesses."
(R.V. Anderson Associates LTD, 2016)
"Although dredging material from the main channel of Trout Creek will mitigate the increased local flood risk and flood level, the mitigation will be temporary as sediment naturally transported down Trout Creek from upstream areas will quickly fill in the dredged areas. The timing of infilling previously dredged areas with new sediment is unpredictable and is likely to occur during major flood event, eliminating the flood mitigation benefit when it is needed most.
Dredging as a flood mitigation measure requires continuous effort and cannot be relied upon to provide flood mitigation when needed."
(George Monbiot, 2014)
"The river channel is not large enough to contain extreme floods, even after dredging. Dredging of river channels does not prevent flooding during extreme river flows … The concept of dredging to prevent extreme flooding is equivalent to trying to squeeze the volume of water held by a floodplain within the volume of water held in the river channel. Since the floodplain volume is usually many times larger than the channel volume, the concept becomes a major engineering project and a major environmental change."