Stream Restoration Load Reduction Estimates (Protocols 1 - 5)

The stream reach must be greater than 100 feet in length and be still actively enlarging or degrading in response to upstream development or adjustment to previous disturbances in the watershed (e.g., a road crossing and failing dams). Most projects will be located on first- to third-order streams, but if larger fourth and fifth order streams are found to contribute significant and uncontrolled amounts of sediment and nutrients to downstream waters, consideration for this BMP would be appropriate, recognizing that multiple and/or larger scale projects may be needed or warranted to achieve desired watershed treatment goals.

The project must utilize a comprehensive approach to stream restoration design, addressing long-term stability of the channel, banks, and floodplain.

Special consideration is given to projects that are explicitly designed to reconnect the stream with its floodplain or create wetlands and instream habitat features known to promote nutrient uptake or denitrification.

Each project must comply with all state and federal permitting requirements, including 404 and 401 permits, which may contain conditions for pre-project assessment and data collection, as well as post-construction monitoring.

Stream restoration is a carefully designed intervention to improve the hydrologic, hydraulic, geomorphic, water quality, and biological condition of degraded urban streams, and must not be implemented for the sole purpose of nutrient or sediment reduction.

There may be instances where limited bank stabilization is needed to protect critical public infrastructure, which may need to be mitigated and does not qualify for any sediment or reduction credits.

A qualifying project must meet certain presumptive criteria to ensure that high functioning portions of the urban stream corridor are not used for in-stream stormwater treatment (i.e., where existing stream quality is still good). These may include one or more of the following:

• - Geomorphic evidence of active stream degradation (i.e., BEHI score)

• - An IBI of fair or worse

• - Hydrologic evidence of floodplain disconnection

• - Evidence of significant depth of legacy sediment in the project reach

Project must meet applicable floodplain management requirements in the stream corridor. Any individual stream restoration project should be assessed with hydrologic and hydraulic models to demonstrate whether it increases water surface elevations or has adverse downstream flooding impacts. In general, these analyses are based on design storm events and flood risk conditions established by the appropriate local or state floodplain management agency (e. g., the 100-year storm event).

Project must evaluate the duration of floodplain ponding in the context of the restoration goals. Micro pools and long-duration ponding of water on the floodplain is essential for amphibian habitat, but large open water features may adversely impact the desired riparian vegetative community. In evaluating a potential restoration site and design, consider the potential adverse effects of extended open water ponding based on the soil characteristics, plant community, amphibian and other aquatic habitat goals.

Project must demonstrate consideration of potential unintended consequences of the restoration. The project should document that a site impairment exists and that the interventions or restoration work proposed are appropriate to address the impairment. The proposed design should demonstrate that a positive ecological functional uplift (or change) for the stream and associated riparian system will result.

Project must demonstrate that it either provides, or is tied into existing upstream and downstream grade controls to ensure the project reach can maintain the intended stream access to the floodplain.

Project must clearly define the boundary of the effective hyporheic zone. For Floodplain Restoration and Raising the Streambed projects the effective hyporheic zone is a maximum of 18 inches deep in the floodplain soil profile, and extends only to those areas that are regularly inundated after the streambed is raised. The actual dimensions must be confirmed by site investigations that define stream flow conditions, root zones, aquifer conditions and the pre-project water table conditions.

Project must demonstrate that baseflow conditions are not reduced as a result of the restoration (ex. change from perennial to seasonal intermittent flow).

Presence of legacy sediment deposits or other floodplain impairment. Legacy sediments must be present in the project reach to a depth that has impaired aquatic ecosystem function. Legacy sediment includes any deposits that have occurred since European settlement, including very recent sediment deposits, often created by features such as mill dams, road embankments, floodplain fill and other kinds of stream corridor impairment.

Floodplain connection to valley bottom aquifer. The design objective is to restore a plant/groundwater connection within the floodplain, so that most of the root mass of the floodplain vegetation is in direct contact with the underlying hyporheic aquifer. In cases where the historic hyporheic aquifer cannot be accessed due to modern controls (i.e., culverts or utility crossings), the objective is to plug the flow of the underlying aquifer so as to create a new hyporheic zone using cobbles, gravel and/or sandy materials.

Defined boundaries for the channel(s), floodplain and valley bottom. The restored channel and floodplain dimensions are based on field testing that define the key vertical and lateral sediment boundaries of the existing floodplain and the hyporheic aquifer beneath it.

Raising the stream bed and removal of legacy sediments are the primary means to restore floodplain reconnection at most sites.

Meet applicable floodplain management requirements in the stream corridor. Any individual stream restoration project should be assessed with hydrologic and hydraulic models to demonstrate whether it increases water surface elevations or adverse downstream flooding impacts. In general, these analyses are based on design storm events and flood risk conditions established by the appropriate local or state floodplain management agency (e.g., the 100-year storm event).

Project extended hyporheic zone and floodplain treatment zone boundaries must be assessed with hydrologic and hydraulic models to demonstrate whether it increases water surface elevations or has adverse downstream flooding impacts.

Project must avoid extended ponding / inundation of the floodplain to assess the potential adverse effects of extended open water ponding based on the soil characteristics, plant community, amphibian and other aquatic habitat goals.

Project must demonstrate consideration of potential unintended consequences of the restoration, such as aquatic passage and potential water quality loss. A site impairment exists and that the interventions or restoration work proposed are appropriate to address the impairment. The proposed design should demonstrate that a positive ecological functional uplift (or change) for the stream and associated riparian system will result.

Any wetlands that fall within the boundaries of the floodplain treatment zone and are reported for credit under Protocol 3 should not also be reported using the Non-Tidal Wetlands Expert Panel.

Project meets all of the qualifying conditions listed in the original Stream Restoration Protocol Expert Panel report outlined in Appendix B.

Project must demonstrate that it either provides, or is tied into existing upstream and downstream grade controls to ensure the project reach can maintain the intended stream access to the floodplain.

Project must clearly define the boundary of the effective hyporheic zone. For floodplain restoration and raising the stream bed projects, the EHZ is a maximum of 18 inches deep in the floodplain soil profile, and extends only to those areas that are regularly inundated after the streambed is raised. The actual dimensions must be confirmed by site investigations that define stream flow conditions, root zones, aquifer conditions and the pre-project water table conditions.

Project must demonstrate that baseflow conditions are not reduced as a result of the restoration. For example, change from perennial to seasonal intermittent flow.

Confirm the presence of legacy sediment deposits.

Demonstrate that the design approach restores channel and floodplain connection with the hyporheic aquifer and restores processes within a hyporheic exchange zone. The EHZ is a maximum of 18 inches deep in the floodplain soil profile. When modern site constraints prevent directly connecting the restored channel and floodplain to the hyporheic aquifer, the design should include measures to interrupt flow within the hyporheic aquifer and elevate the hyporheic exchange zone into the restored floodplain.

Project has defined EHZ boundaries across channels/floodplain.

Legacy sediment removal is the primary floodplain restoration technique.

Eligible runoff reduction practices are: landscape restoration/reforestation; rooftop disconnection; sheetflow to filter/open space; all ESD practices in MD 2007; dry swale; expanded tree pits; grass channels; green roof; green streets; infiltration; rainwater harvesting; landscape restoration/reforestation.

Eligible stormwater treatment practices are: constructed wetlands; filtering practices; proprietary practices; wet ponds and wet swales.

The channel or gully slope below the source must exhibit predictive indicators for severe erosion or hill-slope failure and must be observed to be actively enlarging or degrading.

The project should utilize a comprehensive approach to stream channel design, addressing longterm stability and resiliency of the channel, banks, and floodplain.

Each project must comply with all state and federal permitting requirements, including 404 and 401 permits, which usually contain conditions for pre-and post-project assessment and post construction monitoring.

Projects need to meet post-construction stability criteria and successfully establish needed vegetation. Projects should maintain or improve existing native riparian vegetation in the headwater stream corridor to the extent possible. Projects should follow regulatory agency guidance regarding compensation for any losses of forest, wetlands and sensitive habitats within project work areas.

Projects should avoid the use of pipe extensions or drop structures unless it can be demonstrated that they are needed to sustain channel stability and they do not introduce new aquatic organism passage issues.

The project should provide functional lift within the project reach, typically as indicated by improvements of Levels 2 (Hydraulics) and when possible 3 (Geomorphology) of the stream functions pyramid (Harman et al , 2011).

The project directly addresses a headcut, with severe vertical incision (progressive bedlowering).

The project MUST NOT introduce barriers or challenges to aquatic organism passage or degrade instream habitat. Projects should always seek to improve passage of aquatic organisms and aquatic habitat where possible.

Drop structures, extension of an existing storm drain pipes, stormwater collection features, and scour protection or other hard armoring techniques used in OGSPs are not eligible for credit in perennial or intermittent channels.