Channel Treatments

What – Mini-dams built with straw, logs, or rocks; size depends on channel gradient.

Purpose – Temporary erosion control measure designed to trap and store sediment mobilized from hillslope.  Also intended to reduce downcutting and attenuate peak flows.

Effectiveness – All types of checkdams appear to work better when implemented in gentle gradients, high in the watershed, and placed in a series.  Problems with checkdams include complete structure failure from large storms.  In-channel treatments without adjacent hillslope treatments are ineffective.

Where

• Swales with gentle gradient that allow for sediment storage.
• High-burn severity areas with highly erodible soils.
• Areas with less than 20-percent ground cover.
• Areas with high values at risk.
• Watersheds with small drainage areas, generally less than 5 acres.

Cost – $150–600 each.  Additional factors include:

• Treatment location
• Construction material used (log, straw, or rock) and availability

How to Links - See USDA BAER Catalog page 84 (PDF page 92); and NRCS Rock Check Dam Fact Sheet.

What – Directionally felling trees in a staggered herringbone pattern with tops pointed upstream.

Purpose – Intended to trap floating debris and suspended sediment.  Over time, large woody material dissipates stream energy, provides cover and habitat for fish while providing long-term channel stability.

Effectiveness – Directional felling appears to work better when implemented in gentle gradients, high in the watershed, and placed in a series.  Problems include complete structure failure from large storms.  In-channel treatments without adjacent hillslope treatments are ineffective.

Where

• Areas of high-burn severity.
• Channels where energy dissipation is necessary.
• Channels with unstable bedload and high sediment-loading potential.

Cost – $3500–4000 per mile of treatment, based on approximately 100 trees felled per mile of channel.  Additional factors include:

• Location of treatment area
• Amount of material (trees) available

How to Link – See USDA BAER Catalog page 90 (PDF page 98).

What – Reinforcement of streambank with protective covering, such as rocks, vegetation or engineering materials (including boulders, riprap, and gabion baskets).

Purpose – Reduce bank cutting and erosion due to peak flows.

Effectiveness – No quantitative effectiveness monitoring data exists for this treatment.  Streambank armoring is likely to work better when implemented in gentle gradients, high in the watershed, and placed in a series.  Problems include complete structure failure from large storms.  In-channel treatments without adjacent hillslope treatments are ineffective.

Where

• Highly erodible streambanks.

Cost – moderate to high (no specific estimates are available).  Costs factors listed below:

• Location and access
• Size of material required (which then relates to mechanical equipment or hand labor requirements)

How to Link – See USDA BAER Catalog page 97 (PDF page 105); and National Engineering Handbook - Streambank Armor Protection.

What – Engineered structures such as j-hooks, rock barbs, and single- or double-wing deflectors.

Purpose – Designed to direct increased streamflows and velocities away from unstable banks or structures of value such as a road parallel to the channel.

Effectiveness – There is no documented effectiveness monitoring data for this treatment.  Channel deflectors are likely to work better when implemented in gentle gradients, high in the watershed, and placed in a series.  Problems include complete structure failure from large storms.  In-channel treatments without adjacent hillslope treatments are ineffective.

Where

• Locations where roads are parallel to stream channels.
• Locations where facilities are at risk from streambank erosion or flooding.

Cost – Treatment costs are variable depending on the structure installed.  Costs factors listed below:

• Structure type installed
• Availability of material (rock, jersey barriers, riprap, logs)
• Site location and access

How to Links – See USDA BAER Catalog page 99 (PDF page 107); and Flow Control Structures.

What – Specially engineered and constructed emergency basin for storing large amounts of sediment moving in an ephemeral stream channel.  Designed to trap at least ~ 50–70 percent of expected flows.

Purpose – Designed to store runoff and sediment; often the last recourse to prevent downstream flooding, sedimentation, or threats to human life and property.  Provide immediate protection from floodwater, floatable debris, sediment, boulders, and mudflows.

Effectiveness – No quantitative information is available on effectiveness.  Debris basins are considered to be a last resort because they are expensive to construct and require commitment to long-term repeated maintenance following runoff events.

Where

• Areas with moderate- to high-burn severity.
• Areas where high-value resources are imminently threatened.
• Sites with the capacity to trap the estimated debris flow volume.
• Sites with access available for construction and maintenance.

Cost – Expensive; costs depend on the following factors:

• Location and access
• Size of debris basin
• Availability of material
• Frequency of maintenance

How to Links – See USDA BAER Catalog page 102 (PDF page 110); NRCS Sediment Basin Fact Sheet; and Debris Dam Publication.