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Connecticut Department of Transportation
CLIMATE CHANGE & EXTREME WEATHER PILOT PROJECT
Off ice of Strategic P lanning and Projects
LITCHFIELD HILLS
Lake Waramaug, Warren/Kent/Washington
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
LITCHFIELD HILLS
Covered Bridge, Cornwall
LITCHFIELD HILLS
• 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
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
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
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
CRITICALITY MATRIX
Structure: 06712 Location: Watertown
Year Built: 1966 Criticality Ranking: 4
Very Low to Low Moderate Critical to Very Critical 1 2 3 4 5 6 7 8 9 10
Hydr
aulic
High adaptive capacity Moderate adaptive capacity Low adaptive capacity
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
Spat
ial
Outside FEMA flood zones Within 500 year FEMA flood zone Within 100 year FEMA flood zone
Low concentration of impervious surfaces
Moderate concentration of impermeable surfaces
High concentration of impermeable surfaces
Soci
al
Low ADT & V/C Moderate ADT & V/C High ADT & V/C
0-4 accidents 5 or more accidents Emergency route
Non-NHS, non-emergency route
NHS route Emergency services cluster
Example: Little to No Adaptive Capacity
Criticality Score: 7
02315
Example: Significant Adaptive Capacity
Criticality Score: 8
05417
Legend • Low Risk
• Moderate Risk
e High Risk
National Highway System
Study Region
0 5 20 - - -=====-- - - • Miles
10
Litchfield Hills Study Structures Criticality Rankings
• •
•
N
A
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
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
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
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.
THANK YOU
Project Contacts
Stephanie Molden [email protected]
Michael Hogan, P.E. [email protected]
David Elder, AICP, GISP
0
2
4
6
16 14 12 10
8
18
STRUCTURE NO. 02423 HEADWATER DEPTH VS. PEAK DISCHARGE
20
0 500 1000
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).
1500 2000 2500 3000
PEAK DISCHARGE (CFS)
3500
HEA
DW
AT
ER
DEP
TH (
FT.)
O V
ERTO
PPI
NG
BEG
INS
HW
/D =
1.5
FREE
BO
AR
D =
1 F
T.
100-
YEA
R D
ISC
HA
RG
E
INLE
T SU
BM
ERG
ED
500-
YEA
R D
ISC
HA
RG
E
100-year design headwaterdepth is below the depths at 1-ft freeboard and HW/D = 1.5, therefore structure satisfies headwater design criteria