Mike Jastremski, CFM Watershed Conservation Director

Transcription

1 Planning for Flood Resilient and Fish Friendly Road-Stream Crossings in CT s Northwest Hills Mike Jastremski, CFM Watershed Conservation Director

2 Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Setting priorities Designing replacement projects Integrating with local planning

3 HVA covers the entire Housatonic watershed: MA 149 main-stem miles Roughly 4,200 tributary miles NY CT Riverside in Kent

4 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

5 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

6 Housatonic River Valley, Sharon/Cornwall

7 From Appalachian Trail in Falls Village, looking toward Berkshires Photo: Bill Wakely

8 Morning mist Kent, CT

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10 Presentation Outline Project area Climate threats Field assessment- identify barriers Model flood vulnerability \ Set priorities Design replacement projects Integrate with local planning

11 Climate Threats: More Rain

12 Climate Threats: More Rain July Sharon, CT County Times Source: Litchfield

13 Climate Threats: Water Quality Increase in polluted runoff o Problems with stormwater runoff we re used to

14 Climate Threats: Water Quality and pollution inputs from major floods that we re not as familiar with

15 Climate Threats: Water Quality Bigger floods = stream instability o Increased erosion

16 Climate Threats: Rising Temperatures

17 Climate Threats: Habitat Increasing water temperatures, contracting cold-water habitat

18 Importance of Movement Reproduction Daily and seasonal Movement is Key to Changes in habitat Genetic diversity Adaptation Colonization

19 Roads and Streams Fragmentation Prevents Adaptation Undersized Culverts = More Flood Damage

20 Dams

21 Sub-standard Culverts

22 Housatonic streams in CT

23 Dams not comprehensive!)

24 Roads and railroads

25 Road-stream crossings

26 Dams and crossings

27 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

28 Town-Scale Management Plans 7 towns Evaluate flood risk and conservation value

29 Town-Scale Management Plans Create town-specific Road-Stream Crossing Inventory docs Use Inventory to set priorities

30 Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Town prioritization workshops Designing replacement projects Integrating with local planning

31 Field Assessment

32 Field Assessment

33 Stream Shape: Cross-sectionsection

34 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

35 Stream Shape: Slope

36 Field Assessment Excessive Velocities

37 Inlet Drop

38 Scour Hole

39 Outlet Drop (Perching)

40 Tail Water Armoring

41 Insufficient Water Depth

42 Results Since crossings assessed in project area Barriers common and widespread Many barrier crossings managed by towns with limited resources

43 Stream Habitat Fragmentation Barrier Evaluation Number Percentage Severe barrier % Significant barrier 61 10% Moderate barrier % Minor Barrier % Insignificant Barrier 42 7% No barrier (full passage) 0 0% Of 604 assessed culverts, 356 are moderate to severe barriers 59%!

44 Dams and crossings Fragmentation Prevents Adaptation

45 Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Town prioritization workshops Designing replacement projects Integrating with local planning

46 Simulating Flood Risk How do we predict whether or not this culvert will flood the road? Culvert Inlet

47 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

48 Undersized Culverts = More Flood Damage

49 Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Town prioritization workshops Designing replacement projects Integrating with local planning

50 Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Town prioritization workshops Designing replacement projects Integrating with local planning

51 Design Phase Leverage limited funding Enormous scale of problem Build capacity at municipal level

52 Stream Simulation Design Road-stream crossing design that mimics the natural stream channel through a structure, as if the crossing didn t exist.

53 Stream Shape: Cross-sectionsection

54 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

55 Stream Shape: Slope

56 Stream Simulation Design Width of a Stream Simulation Design structure is spans the natural bed and banks.

57 Stream Simulation Design

58 Stream Simulation Design Minimizes stream skew

59 Stream Simulation Design Substrate designed to replicate natural streambed allowing for mobility and dynamic response to the need for additional capacity.

60 Flood Resiliency Provides sufficient hydraulic capacity and passage of debris

61 Flood Resiliency Reduces the likelihood of clogging, upstream ponding, and road overtopping.

62 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

63 Economic Benefits These cost saving factors will become more and more relevant as storms increase in both intensity and frequency due to climate change.

64 Economic Benefits Stream Sim = New Funding Opportunities

65 Stream Simulation Design Stream Simulation Design is good for everyone: Economic benefits for local communities Habitat improvement for native species Resilient infrastructure

66 Presentation Outline Project area Climate threats Field assessment Modelling flood vulnerability Town prioritization workshops Designing replacement projects Integrating with local planning

67 Town-Scale Management Plans Combine: Inventory Ranking Conceptual designs Supporting information Adopt as part of Hazard Mitigation Plan

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69 Partners, Funders and Advisors Housatonic River NRD Trustees Town of Cornwall, CT