DEEP: Hydromodification Management Measures

Connecticut's Coastal Nonpoint Source Pollution Control Program


This category of NPS pollution includes channelization (straightening, widening, deepening or relocating rivers or streams to improve flood control, navigation, or drainage), dam construction and maintenance, and streambank and shoreline erosion.  Channelization can adversely impact in-stream and streamside fish and wildlife habitat, and alter water temperature and sediment transport patterns.  Structural hardening of channels can displace habitat, increase stream flow, and carry NPS pollutants from the upper reaches of watersheds into coastal waters.  Dam construction and maintenance can alter river hydraulics and degrade in-stream habitat and water quality.  Erosion of streambanks and shorelines is a natural occurrence, but excessive sediment levels can smother submerged aquatic vegetation, cover shellfish beds and tidal flats, fill in tidal pools, and contribute to increased levels of turbidity and nutrients.   

Key Concepts

1. Channelization and Channel Modifications

Evaluate and reduce the potential effects of channels on the physical and chemical characteristics of surface waters and on in-stream and streamside habitat.

Operate and maintain existing channels to improve surface water characteristics and restore in-stream and streamside habitat.

2. Dams

Control erosion and sedimentation during construction and maintenance.

Evaluate impacts to surface water quality and in-stream and streamside habitat during dam operation and surface water withdrawal.

Properly store and dispose of chemicals and other substances used in dam construction or maintenance, including concrete additives, solid wastes, pesticides, and fertilizers.

3. Streambank and Shoreline Erosion

Where streambank or shoreline erosion is a nonpoint source problem, stabilize eroding streambanks and shorelines using vegetative methods wherever possible.

Protect streambank and shoreline features such as wetlands and streamside areas with the potential to reduce nonpoint source pollution.

Protect streambanks and shorelines from erosion due to uses of the shorelands or adjacent surface waters.

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