NCD for Extreme Event Stream Restoration and Improved Resilience
Thomas A. Graupensperger
NCD Restoration Designer
Dewberry
Mechanicsburg, PA
This session will present project examples where vulnerable, extreme event impacted infrastructure was restored and resilience improved by using Natural Channel Design (NCD) Restoration and Stabilization techniques. Extreme weather events continued throughout the east coast states in 2018 and into early 2019, with record rainfall amounts in many locations throughout Central Pennsylvania, surrounding Mid-Atlantic and Southeast Regions. How can we design for these more numerous and more extreme events in the future, while mitigating increased storm/flood flows, volumes and meet water quality requirements?
We will look at opportunities where gray and green/nature-based infrastructure rehabilitation and replacement are paired effectively with stream restoration/stabilization activities for improved resilience. By effectively integrating resilient gray and green/natural-nature based infrastructure (NNBI) improvements; the creation, restoration, and reconnection of natural resources (floodplains/wetlands/riparian buffers/aquatic habitat) can also result in triple bottom line benefits including TMDL credits and continued opportunities for pollution reduction within the Chesapeake Bay and other watersheds.
Understanding the storm event, failure mechanisms, and associated existing/pre-existing conditions associated prior upstream alterations and previous extreme event required maintenance/management measures is critical to determining the appropriate restorative measures that will survive severe weather events. To predict and model proposed stream restoration treatments and develop resilient scour countermeasures, we need to understand and evaluate the contributing watershed hydrogeomorphic vulnerabilities, failure mechanisms and sediment sources/transport characteristics.
The presentation will revisit and provide an overview/review of several case studies, where extreme events resulted in major infrastructure impacts and outline site hazard mitigation, restoration approaches implemented. This presentation and specific case study will identify site hazard mitigation, restoration approaches, considerations and opportunities for:
Extreme event resiliency through redundant measures
Flood/Shear Vulnerability Assessment/Analyses
Proactive vs Reactive Channel Instability Restoration/Hazard Mitigation
Hydrologic Mitigation- (Reduce/Delay/Desynchronize Peak Flows) with Floodplain Reconnection/Wetlands/Forest Buffer/Reforestation
Local & Regional Sediment Management/Transport
Habitat restoration and enhancement
MS4-TMDL, Pollutant Reduction Credits
About Thomas A. Graupensperger
Tom has more thirty-nine (39) years of experience providing municipal, water resources and transportation environmental services including (soils, geologic hazards, groundwater, waste sites) inventories, assessments, mitigation and permitting (NPDES, 401, 404). Participated in numerous public hearings, meetings and advisory committees related to projects; managed, designed and permitted numerous projects which involved environmental mitigation and pollutant reductions. Performed ecological restoration of stream channels, wetlands, floodplains, riparian buffers, dam removals, urban and disturbed lands throughout the Mid-Atlantic Region and its many Physiographic Provinces. Rosgen certified in natural stream channel assessment and design, with an experience record including more than 250 acres of constructed floodplain-wetlands and reconnections, more than seven (7.5) miles of natural stream channel restorations and stabilizations as well as numerous structural and non-structural non-point source best management practices –stormwater control measures- green stormwater infrastructure and erosion and sediment pollution controls. Tom routinely performs construction oversight and consultation on majority of natural channel design restorations and experience includes Design-Build project restorations.