Stream Restoration as a BMP

Transcription

1 Stream Restoration as a BMP Development of a National Performance Database and Crediting Guidance Marc Leisenring, P.E. Geosyntec Consultants ACWA Stormwater Summit May 9, 2018 Eugene, OR

2 WERF-U5R14: Stream Restoration BMP Database Module Develop a scientifically based set of stream restoration reporting protocols for water quality and develop a national database to store information on these projects. WERF-IT13 Stream Restoration as a BMP (Crediting) Develop a framework document and consistent approach for estimating pollutant reduction credits for stream restoration as a BMP.

3 Built Upon Science: The International Stormwater BMP Database Philosophy, vision and lessons learned starting point for a Stream Restoration BMP Database

4 What is the BMP Database? Coalition of Sponsors over 20 Years: A collection of BMP study data and summary reports Researchers, agencies, and others voluntarily submit data in standardized format Data is reviewed by project team and uploaded to master database Data and project findings are publically available through 4

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6 One-stop Shop for Science-based Performance Data Urban Stormwater BMPs (Source Controls, Structural, GI/LID) Agricultural BMPs Stream Restoration Construction BMPs Clean Water Act Goals Fishable & Swimmmable

7 Stream Restoration for Water Quality Management

8 Urbanized Streams Loss of Function Modified hydrology Eroding banks and headcuts Channelization Floodplains and wetlands disconnected Limited upstream sediment supply Lack of vegetated buffers Nutrient enrichment Functional pyramid adapted from Harman et al. 2012

9 WQ Improvement Goals of Restoration Projects Reduce bank and channel erosion Reduce downstream sediment loadings Reduce downstream nutrient loadings Reduce in-stream TSS and turbidity Reduce in-stream nutrient concentrations Reduce in-stream temperature Increase in-stream dissolved oxygen Wohl et al. (2015)

10 Stream Restoration Database Structure and Initial Contents

11 What is the Stream Restoration Database (SRDB)? Centralized repository stream restoration studies Performance data and metadata that document the variables and practices that reduce pollutant loading from stream restoration projects Developed and initially populated in 2016

12 SRDB Structure Stream Characteristics Restoration Practice Design Characteristics Study Design/ Monitoring Methods Site/Watershed Characteristics Data/ Performance Results Project/Study Information Stream Restoration Database Cost Data

13 Studies in the Database Initial 24 studies

14 Use of Database Information Improve understanding of governing processes in natural systems Develop estimates of TSS, N and P load changes Gather enough generalized metrics and indices to improve confidence for application of techniques elsewhere Assess data uncertainty and natural variation Assign pollutant reduction credits based on measured stream restoration benefits Evaluate functional assessment approaches

15 Credit Estimation Approaches Stream Restoration

16 Stream Restoration Strategies Included Bed and bank stabilization Riparian buffers Excluded Channel reconfiguration Watershed processes Floodplain reconnection In-stream enhancement prweb.com

17 Bank and Bed Stabilization Limit loading from a potentially large sediment and nutrient source Characterize bank and bed materials (bulk density and phosphorus concentrations) Estimate annual erosion rates Big Dry Creek, Westminster, CO Big Dry Creek, Westminster, CO NRCS, Schumm et al. (1984)

18 Riparian Buffers High plot-scale removal, but in-stream benefits less certain T. Shultz; Department of NREM, Iowa St. Univ.

19 Riparian Buffer Performance Nitrogen Influent loading and infiltration Time GW intersects root zone Denitrification rates: f(carbon) N Loading Carbon Sediment and Phosphorus Influent loading Trap efficiency: f(width, density, and slope)

20 Floodplain Reconnection Settling of particulate nutrients and biotic and abiotic removal Access wetlands and overbank Up to 10% of river loads retained The Nature Conservancy Willamette River Initiative

21 Floodplain Reconnection Performance Estimate volume and loads interacting with floodplain Stage-duration curve derived from flowduration and stream rating curve Requires instream water quality and longterm flow record (or model estimates) Removal rates uncertain; dependent on floodplain characteristics and flow path Wetland performance as initial estimate Average Daily Stage (ft) % 20% 40% 60% 80% 100% % of Days Equaling or Exceeding Stage

22 In-Stream Enhancement Structure installation increases hydraulic retention times and hyporheic exchange Subsurface organic carbon availability can increase denitrification Wolf Water Resources (2017)

23 In-Stream Enhancement Performance Hyporheic box assumed (Chesapeake Bay approach) or direct hyporheic flux quantification Measured or assumed denitrification rate Upstream/Downstream subsurface water quality measurements Schueler and Stack (2013)

24 Conclusions and Future Research

25 Conclusions Benefits of stream restoration clear, but site-specific and highly variable Additional research and data is required to support quantification of benefits More standardized monitoring and performance assessment is required to evaluate and refine crediting approaches Restoration planning should be holistic and watershed-scale

26 Future Research Need additional research to inform quantification approaches for all restoration practices More representative and standardized data from various regions/stream types (e.g. southwest, ephemeral streams) Improve functional assessment procedures that can be verified with performance studies Determine saturation point or upper limit of streams nutrient retention capabilities

27 Questions? WRF Program Director Harry Zang, P.E. Project Team Contacts Co-Principal Investigators: Jonathan Jones, P.E. Eric Strecker, P.E. Brian Bledsoe, P.E., Ph.D., Team Members: Jane Clary, Rod Lammers, Marc Leisenring, P.E. Scott Struck, Ph.D. Adam McGuire,