Planning for Flood Resilient and Fish Friendly Road-Stream Crossings in CT s Northwest Hills Mike Jastremski, CFM Watershed Conservation Director
Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Setting priorities Designing replacement projects Integrating with local planning
HVA covers the entire Housatonic watershed: MA 149 main-stem miles Roughly 4,200 tributary miles NY CT Riverside in Kent
HVA covers the entire Housatonic watershed: MA The Housatonic River: 149 miles long Vertical drop of 1,430 feet 83 towns in 3 states NY CT and emptying into Long Island Sound at Stratford and Milford Point, CT
HVA covers the entire Housatonic watershed: MA The Housatonic River: 149 miles long Vertical drop of 1,430 feet 3 states and 83 towns 1,948 square miles (1.2 million acres) NY CT
Housatonic River Valley, Sharon/Cornwall
From Appalachian Trail in Falls Village, looking toward Berkshires Photo: Bill Wakely
Morning mist Kent, CT
Presentation Outline Project area Climate threats Field assessment- identify barriers Model flood vulnerability \ Set priorities Design replacement projects Integrate with local planning
Climate Threats: More Rain
Climate Threats: More Rain July 2013 - Sharon, CT County Times Source: Litchfield
Climate Threats: Water Quality Increase in polluted runoff o Problems with stormwater runoff we re used to
Climate Threats: Water Quality and pollution inputs from major floods that we re not as familiar with
Climate Threats: Water Quality Bigger floods = stream instability o Increased erosion
Climate Threats: Rising Temperatures
Climate Threats: Habitat Increasing water temperatures, contracting cold-water habitat
Importance of Movement Reproduction Daily and seasonal Movement is Key to Changes in habitat Genetic diversity Adaptation Colonization
Roads and Streams Fragmentation Prevents Adaptation Undersized Culverts = More Flood Damage
Dams
Sub-standard Culverts
Housatonic streams in CT
Dams not comprehensive!)
Roads and railroads
Road-stream crossings
Dams and crossings
Project Goals Respond to climate threats and scale of barrier problem: Identify replacement projects that both reduce flood risk and reconnect important habitat Build local capacity to take advantage of every opportunity to replace problem culverts
Town-Scale Management Plans 7 towns Evaluate flood risk and conservation value
Town-Scale Management Plans Create town-specific Road-Stream Crossing Inventory docs Use Inventory to set priorities
Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Town prioritization workshops Designing replacement projects Integrating with local planning
Field Assessment
Field Assessment
Stream Shape: Cross-sectionsection
Stream Shape: Pattern Pattern is a stream s shape from above Placement of features like meander bends, pools and riffles Adapted from North Carolina Cooperative Extension Service, 1999
Stream Shape: Slope
Field Assessment Excessive Velocities
Inlet Drop
Scour Hole
Outlet Drop (Perching)
Tail Water Armoring
Insufficient Water Depth
Results Since 2013 900 + crossings assessed in project area Barriers common and widespread Many barrier crossings managed by towns with limited resources
Stream Habitat Fragmentation Barrier Evaluation Number Percentage Severe barrier 151 25% Significant barrier 61 10% Moderate barrier 144 24% Minor Barrier 206 34% Insignificant Barrier 42 7% No barrier (full passage) 0 0% Of 604 assessed culverts, 356 are moderate to severe barriers 59%!
Dams and crossings Fragmentation Prevents Adaptation
Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Town prioritization workshops Designing replacement projects Integrating with local planning
Simulating Flood Risk How do we predict whether or not this culvert will flood the road? Culvert Inlet
Force CREST Model HVA is partnering with UCONN CREST Model Combining the model with field data, UCONN can simulate which crossings will flood the road Distributed Variables Land Cover Soil Properties Vegetation Library Impervious Area GIS-Terrain elevation flow direction Stream network Remotely Sensed Products Leaf Area Index Water Balance Interception Evaportranspiration Snow Process Infiltration ET Runoff Fully Distributed Routing Routing parameters T W Hourly MeteorologIc Variables climatology Precipitation Energy Balance Atmospheric Layer Canopy Layer Snow Pack Layer Surface Soil Layer Deep Soil Layer River discharge (Q) USGS (Q) Calibration
Undersized Culverts = More Flood Damage
Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Town prioritization workshops Designing replacement projects Integrating with local planning
Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Town prioritization workshops Designing replacement projects Integrating with local planning
Design Phase Leverage limited funding Enormous scale of problem Build capacity at municipal level
Stream Simulation Design Road-stream crossing design that mimics the natural stream channel through a structure, as if the crossing didn t exist.
Stream Shape: Cross-sectionsection
Stream Shape: Pattern Pattern is a stream s shape from above Placement of features like meander bends, pools and riffles Adapted from North Carolina Cooperative Extension Service, 1999
Stream Shape: Slope
Stream Simulation Design Width of a Stream Simulation Design structure is spans the natural bed and banks.
Stream Simulation Design
Stream Simulation Design Minimizes stream skew
Stream Simulation Design Substrate designed to replicate natural streambed allowing for mobility and dynamic response to the need for additional capacity.
Flood Resiliency Provides sufficient hydraulic capacity and passage of debris
Flood Resiliency Reduces the likelihood of clogging, upstream ponding, and road overtopping.
Economic Benefits Lower long-term cost over the lifespan of the structure as compared to an in kind replacement: Less maintenance Less repair Reduced flood damage
Economic Benefits These cost saving factors will become more and more relevant as storms increase in both intensity and frequency due to climate change.
Economic Benefits Stream Sim = New Funding Opportunities
Stream Simulation Design Stream Simulation Design is good for everyone: Economic benefits for local communities Habitat improvement for native species Resilient infrastructure
Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Town prioritization workshops Designing replacement projects Integrating with local planning
Town-Scale Management Plans Combine: Inventory Ranking Conceptual designs Supporting information Adopt as part of Hazard Mitigation Plan
Partners, Funders and Advisors Housatonic River NRD Trustees Town of Cornwall, CT