Office of Strategic Planning and Projects Connecticut Department of Transportation CLIMATE CHANGE & EXTREME WEATHER PILOT PROJECT

Transcription

1 Office of Strategic Planning and Projects Connecticut Department of Transportation CLIMATE CHANGE & EXTREME WEATHER PILOT PROJECT

2 LITCHFIELD HILLS Lake Waramaug, Warren/Kent/Washington

3 LITCHFIELD HILLS Northwest corner of Connecticut, historic, pastoral landscape at the foothills of the Berkshires (Appalachian range) Population: 185,000 Land area: 920 sq. mi. Density: 206 people/sq. mi. Manhattan: 66,940 people/ sq. mi. Economy: tourism, dairy farming, manufacturing Older transportation infrastructure

4 LITCHFIELD HILLS Covered Bridge, Cornwall

5 LITCHFIELD HILLS

6 Today s roads follow path of many Native American trails: Northwest Path is similar to Route 44 Berkshire Path is like Route 7 Old Connecticut Path is similar to Route 6

7 STUDY STRUCTURES More than 135 structures were identified in the study area that met the review criteria Average structure age: 81 years 52 Structures underwent hydraulic evaluations 34 study structures satisfy hydraulic design criteria *13 of those vulnerable to scour due to velocity 18 study structures do not satisfy hydraulic design criteria 19 structures are critical

8 ASSESSMENTS Hydraulic Evaluations Performance (Rating) curves for structures: Headwater depth vs. peak discharge Velocity vs. peak discharge Criticality/Vulnerability Assessments: Criticality Matrix Criticality ranking for structures

9 ANALYSIS RESULTS Following slides are examples of: Results of performance curve calculations and adaptive capacity analyses Results of Criticality/Vulnerability assessments Maps of study and structure areas Low, Moderate, and High Risk structures

10 CRITICALITY MATRIX Structure: Location: Watertown Year Built: 1966 Criticality Ranking: 4 Very Low to Low Moderate Critical to Very Critical High adaptive capacity Moderate adaptive capacity Low adaptive capacity Hydraulic No history of closure History of periodic closures Significant history of closure Scour critical Satisfies WSE criteria Adjacent to scour critical structures Does not satisfy WSE criteria Outside FEMA flood zones Within 500 year FEMA flood zone Within 100 year FEMA flood zone Spatial Low concentration of impervious surfaces Moderate concentration of impermeable surfaces High concentration of impermeable surfaces Low ADT & V/C Moderate ADT & V/C High ADT & V/C Social 0-4 accidents 5 or more accidents Emergency route Non-NHS, non-emergency route NHS route Emergency services cluster

11 Example: Little to No Adaptive Capacity

12 02315 Criticality Score: 7

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14 Example: Significant Adaptive Capacity

15 05417 Criticality Score: 8

16

17 Litchfield Hills Study Structures Criticality Rankings Legend Low Risk Moderate Risk e High Risk National Highway System Study Region ===== Miles N A

18 PROJECT FINDINGS Factors related to Resiliency: Velocity-erosion-scour impact vulnerability and adaptive capacity Many structures near end of their service life may be more vulnerable Hydraulic design methods of older structures are unknown Precipitation Estimates Precip.net vs. TP-40 NOAA Atlas 14 will be used when released Precip.net estimates higher for less frequent storm events (500, 100, 50 year) Example of bridge scour, New Milford

19 PROJECT FINDINGS Keep data/tools up to date (rainfall, stream gage, regression equations) Check frequency discharge should be carefully examined Reassess hydrologic methods and practices with or in anticipation of release of NOAA Atlas 14 NOAA Atlas 14 not available yet for Connecticut 19

20 NEEDS / FURTHER RESEARCH Precipitation projections from climate models Uncertainty in precipitation/discharge estimates vs. uncertainty in climate change projections Guidelines, examples and tools to conduct risk and cost benefit analyses Developing and integrating cost factors into criticality assessments

21 NEXT STEPS Outline a plan/process to better incorporate risk assessment/life cycle cost-benefit analysis into hydraulic design and asset management Discuss updating regression equation with USGS and seek funding to study Re-establish statewide hydrology committee Work with municipalities on context dependent adaptation strategies and other tools for at-risk structures Stay current with studies, best practices, guidance, and revisions to FHWA s Climate Change and Extreme Weather Vulnerability Assessment Framework.

22 THANK YOU Project Contacts Stephanie Molden Michael Hogan, P.E. David Elder, AICP, GISP

23 STRUCTURE NO HEADWATER DEPTH VS. PEAK DISCHARGE year design headwaterdepth is below the depths at 1-ft freeboard and HW/D = 1.5, therefore structure satisfies headwater design criteria HEADWATER DEPTH (FT.) YEAR DISCHARGE 500-YEAR DISCHARGE INLET SUBMERGED HW/D = 1.5 Continuing with the example presented in Figure 2, a 2-inch or an approximate 24% increase in the 100-year, 24-hour precipitation would increase the current 100-year peak discharge estimate of 881 cfs by 366 cfs to 1,247 cfs (horizontal scale), a 41.5% increase. As illustrated by the rating curve, a 2-inch increase in precipitation would move the 100-year peak discharge estimate to slightly above the current 500-year peak discharge estimate of 1,221 cfs. The resulting headwater depth would increase by approximately 1.9-ft, from 6.9-ft to 8.8-ft (vertical scale). FREEBO ARD = 1 FT. O VERTO PPING BEGINS PEAK DISCHARGE (CFS)