Pocosham Creek Stream Restoration Post-Construction Monitoring
The City of Richmond Department of Public Works engaged Hazen to provide post-construction monitoring services for the Pocosham Creek Stream Restoration. Approximately 8 square miles of 20% impervious watershed drains to the Pocosham Creek project site totaling 5,300 linear feet. The project reconnected the stream with its floodplain; it now provides 60 acre-feet of temporary floodplain storage during storm events.
Monitoring is required by the US Army Corps of Engineers and the Virginia Department of Environmental Quality for five years, with an interim report released each year comparing each year’s results to the initial baseline.
Monitoring work completed by Hazen included:
- Stream Profile Survey: Profiling stream thalweg (deepest portion of stream) to document bed features, water depths and low bank elevations for 5,300 LF of restored stream. Profiling included the locations, depths and slopes of riffles, pools, glides and runs.
- Cross-Section Survey: Stream cross-section measurements at five locations.
- BANCS Analysis: Bank Assessment for Non-point Source Consequences of Sediment assessments utilizing the Bank Erosion Hazard Index and Near Bank Stress ratings to estimate bank erosion rates.
- Particle Counts: Seven particle counts taken at riffles and pool to evaluate bed conditions.
- Structure Evaluation: Stone structure visual inspection based on the presence of aggradation (filling), degradation (erosion) or flanking.
- Rapid Bioassessment Protocol: Completing the EPA’s Rapid Bioassessment Protocol for Use in Streams and Wadable Rivers evaluations.
- Vegetation Ploy Surveys: Establishing five 400 ft2 tree plots and 9 ft2 grass plots to track plant growth.
- Bank Pin Surveys: Installing bank pins at eight stream meanders to quantify bank erosion and monitor stream pattern.
All streams are in flux, balancing water and sediment movement using the least amount of energy. Instability, defined as change (happening slowly or suddenly) which exceeds certain thresholds, creating imbalance requires a stream to change its form to re-achieve stability. Hazen is on the watch for instability and will design corrections if needed. The constructed site is stable and meeting project goals. Continued annual monitoring of the Pocosham Creek stream restoration project will be a critical aspect of verifying the project’s success.
Continuing, Comprehensive Support
Our staff conducts regular monitoring to ensure continued project stability.
Project Outcomes and Benefits
- Constructed site is stable and meeting project goals.
- Provides 60 acre-feet of temporary floodplain storage during storm events.
- Several stone structures (e.g. constructed riffles, J-hooks, rock vanes) provide grade control against incision (vertical erosion) and lateral migration (horizontal erosion).
- Hazen will conduct continued annual monitoring of the project and will design corrections if needed.