Regenerative design: A blend of ecological engineering and restoration design as an approach to restoration of ecosystem services

Background/Question/Methods Many stream channels have been degraded by urban runoff.  In addition to the sediment and nutrient loading, their degradation has resulted in the reduction of important habitat as well as ecosystem services.  The use of stream and wetland restoration techniques, together with performance enhancing modifications (i.e., carbon and iron supplementation) applied with a focus towards enhancing/restoring ecosystem function and delivery of services, suggests we can make significant positive contributions to the quality and quantity of our watershed resources and improve the quality of life in our local communities.  In ephemeral or intermittent drainage channels, a carbon-rich granular substrate (e.g., sand to gravel with 20% V:V shredded wood) to fill the eroded channel, a series of constructed pools and riffle structures to provide non-erosive conveyance, and on-grade seepage wetlands to capture and treat the pulsed storm water runoff, all work together to provide a ‘natural’ system with enhanced properties that delivers a suite of services important to meeting water quality goals while supporting native flora and fauna, including local human communities.  In perennial streams, the incised stream channel is raised (where feasible), to reconnect peaky urban discharges to the adjacent riparian/floodplain corridor through the placement of boulder and riffle grade controls.  In addition, riparian/floodplain storage is increased through the construction of on-grade seepage wetlands.

Results/Conclusions To date, monitoring and research have documented the positive effects on urban hydrology (i.e., reduced peak discharge, increased flow concentration time), water quality (i.e., sediment and nutrient discharge load reductions), habitat (e.g., species diversity and density), quality of life (e.g., increased useage), as well as other metrics of ecosystem services (e.g., groundwater supply).  Monitoring work conducted by the University of Maryland demonstrates storm water quantity benefits (e.g., reduction in peak discharge and increased Time of Concentration), as well as water quality benefits (e.g., reduction of Total Suspended Sediments and Total Nitrogen).  Generally, this approach costs a fraction of the standard engineering approach (i.e., drop structures, pipe, concrete outfalls), requires a smaller disturbance area, and is highly valued for aesthetics by the adjacent property owners. This approach has been adopted by the State of Maryland in a July 2011 Draft document titled “Accounting for Stormwater Wasteload Allocations and Impervious Acres Treated: Guidance for NPDES Stormwater Permits” where this approach was adopted as a best management practice with TSS, TP, and TN removal efficiencies of 90%, 60%, and 50%, respectively.