Connecticut's Coastal Nonpoint Source
Pollution Control Program
Hydromodifications

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 stream bank and shoreline erosion. Channelization can adversely impact in-stream and stream-side 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 stream banks 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 stream-side habitat.
• Operate and maintain existing channels to improve surface water characteristics and restore in-stream and stream-side habitat.

2. Dams

• Control erosion and sedimentation during construction and maintenance.
• Evaluate impacts to surface water quality and in-stream and stream-side 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. Stream Bank and Shoreline Erosion

• Where stream bank or shoreline erosion is a nonpoint source problem, stabilize eroding stream banks and shorelines using vegetative methods wherever possible.
• Protect stream bank and shoreline features such as wetlands and stream-side areas with the potential to reduce nonpoint source pollution.
• Protect stream banks and shorelines from erosion due to uses of the shorelands or adjacent surface waters.

Related Links

Content Last Updated February 28, 2020