Channel bed stabilization is used to stabilize the bed or bottom of a channel. Channel bed stabilization can support one or more of the following goals: maintaining or altering channel bed elevation or gradient; modifying sediment transport or deposition; and/or managing surface water and groundwater levels in ﬂoodplains, riparian areas, and wetlands. Channel bed stabilization is an in-channel practice.
Figure 15. Channel bed stabilization. Credit: FABE, The Ohio State University.
Channel bed stabilization applies to the beds of existing or newly constructed alluvial or threshold channels undergoing damaging aggradation (deposition of material by a river, stream, or current) or degradation that cannot be feasibly controlled by clearing or snagging, establishment of vegetative protection, installation of bank protection, or installation of upstream water control measures. Channel bed stabilization also applies to channels where the removal of barriers to aquatic organism passage would result in destabilization of the channel bed.
The primary purpose of channel bed stabilization measures is to prevent or reduce soil erosion associated with bed and mass bank failures.
The effectiveness and water quality beneﬁts of channel bed stabilization measures are very site-speciﬁc. Channel bed stabilization practices should be incorporated in order to:
- prevent bed instability. Bed instability can result in channel bank failures and the movement of large amounts of sediment downstream.
- aid in maintaining the ﬂow or storage capacity of the channel or impoundment.
- reduce the downstream effects of sediment resulting from bed erosion.
- maintain or restore channel meanders that would enhance the channel conditions.
- improve or enhance the stream corridor for ﬁsh and wildlife habitat, aesthetics, and recreation.
- Measures must not:
- impair the ﬂoodway or ﬂoodplain functions.
- cause detrimental changes in water surface elevations when water surface elevations are a concern.
- impede the upstream or downstream passage of aquatic organisms, unless the objective is to restrict the access of invasive species.
- Clear the channel to remove stumps, fallen trees, debris, and sediment bars only when they are causing, or could cause, detrimental bank erosion, structural failure, or reduction of channel capacity that results in above-average overﬂows on adjacent ﬂoodplains. Retain or replace habitat-forming elements that provide cover, food, pools, and water turbulence to the extent possible. Note that removal of any material on the bed of a channel will, in many cases, require regulatory permission. Check with your local SWCD or NRCS to see if permission is needed for your situation.
- Prepare plans and speciﬁcations for speciﬁc channel reaches and ﬁeld sites. Plans should describe the requirements for applying the practice to achieve its intended purpose(s). At the minimum, plans should include:
- a topographic map.
- the size of the drainage area.
- estimates of the design velocities.
- safety considerations.
- Dispose of spoil material from clearing, grubbing, and channel excavation in a manner that will not interfere with the function of the channel. Protect from erosion all disturbed areas around the bed stabilization measures. Select vegetation or other measures that are best suited for the anticipated site conditions.
- NRCS Conservation Practice Standard 584 contains other provisions that should be considered. It is recommended that you read that if you decide bed stabilization is needed.
- It is important that stabilization methods be designed and installed according to a site-speciﬁc plan in accordance with all local, state, tribal, and federal laws and regulations. Also, only apply measures that are compatible with improvements planned or being carried out by others. In Ohio, regulations relating to agricultural ditches, modiﬁed streams, and natural streams and rivers are complex. It is recommended that before doing any work on one of these systems, you check with your local SWCD or NRCS to determine what, if any, permits and/or permissions are needed. Aspects of NRCS Conservation Practice Standard 584 might pertain to your situation.
- Sufficient effort needs to be taken to identify the causes contributing to the instability of the channel. Watershed alterations resulting in signiﬁcant changes in discharge or sediment production need to be understood. Due to the complexity of such an assessment, consider using an interdisciplinary team and watershed modeling.
- Evaluate the effects of channel work on existing structures such as culverts, bridges, buried cables, pipelines, and irrigation ﬂumes to determine the impact on their intended functions. Analyze the quantity and character of sediments entering the channel reach being evaluated on the basis of both present and projected conditions caused by changes in land use, land treatment, and upstream improvements or structural measures. Select measures that are compatible with the bank or shoreline materials, water chemistry, channel hydraulics, and slope characteristics, both above and below the waterline.
Costs are site-speciﬁc and will depend on the size and type of streambank stabilization measures needed at a location. In some cases, cost-sharing funds might be available, depending on the size of the needed bed stabilization and the type of measures used.
Channel bed stabilization practices help maintain self-sustaining ﬂow conditions that do not cause down-cutting of the channel. Obstructions that cause turbulence and local scour problems might be removed in some cases. Rock and wood structures might be included in a bed stabilization plan to create a more natural pool-and-riﬄe sequence or to deﬂect ﬂow away from the banks.
Extensive design details are provided in NRCS Standard 584: Channel Bed Stabilization