MnDOT Flash Flood Vulnerability and Adaptation Assessment Pilot Project

January 2015

Project Background

• Minnesota GO Vision & Statewide Multimodal Transportation Plan identified the risk of flash flooding as a result of changing precipitation patterns due to climate change.

• From 1958 to 2011, 45% increase in very heavy precipitation in the Midwest (NOAA)

MnDOT’s Pilot Project Objectives

• Better understand the trunk highway network’s risk from flash flooding

• Identify cost-effective options to improve the network’s resiliency

• Support MnDOT’s asset management planning

• Provide feedback to FHWA on the Draft Framework

4

Funded by FHWA Climate Change Resilience Program

• Program Goals:• Advance transportation climate resilience activities• Assist FHWA in building the Vulnerability Framework into an

Adaptation Framework

• Funded 5 pilot projects in 2010-2010 to test an assessment conceptual model

• Funded 19 pilot projects, including Minnesota, in 2013 as part of an effort to test the Framework

Project Roles and Responsibilities

Consultant:

Pilot Project Overview

• Phase 1: System-wide vulnerability assessment– High-level screen of trunk highway network in Districts 1

& 6

• Phase 2: Facility-level adaptation analysis– Two high risk facilities (one in each district)

Defining Vulnerability“Climate change vulnerability in the transportation context is a function of a transportation system’s exposure to climate effects, sensitivity to climate effects, and adaptive capacity.” (Vulnerability Framework)

• Exposure- whether the asset or system is locatedin an area experiencing direct impacts of climate change

• Sensitivity - how the asset or system fares when exposed to an impact • Adaptive capacity - the systems’ ability to adjust or cope with existing climate variability or future climate impacts

Systemwide Vulnerability Assessment Approach

Criteria WeightingExample: Culverts

% change in design flow for

overtopping60%Channel Condi-

tion Rating15%

Culvert Condi-tion Rating

25%

Stream Velocity20%

Previous Flood Issues35%

Belt Width to Span Length Ra-

tio10%

% Drainage Area Forest10%

% Drainage Area not Lakes/Wet-

lands10%

% Drainage Area Urban15%

AADT35%

HCADT25%

Detour Length35%

Flow Control Regime5%

Sensitivity

Exposure

AdaptiveCapacity

Number of Assets Scored

Bridges Large Culverts Pipes

Roads Paralleling

Streams(segments)

Total

District 1 140 160 543 18 861District 6 176 361 377 44 958Total 316 521 920 62 1,819

Highly vulnerable (Tier 1 and 2) assets are not necessarily in imminent danger of flooding, nor are lower vulnerability assets immune from flooding. Values are indicators of relative vulnerability compared with other assets in the same district.

Highly vulnerable (Tier 1 and 2) assets are not necessarily in imminent danger of flooding, nor are lower vulnerability assets immune from flooding. Values are indicators of relative vulnerability compared with other assets in the same district.

Vulnerability By Asset TypeDistrict 6

Roads Parallel-ing Streams

Bridges Large Culverts Pipes0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Perc

ent a

ge o

f Ass

ets

Roads Parallel-ing Streams

Bridges Large Culverts Pipes0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

District 1

Vulnerability By Asset Type

Tier 1 Tier 2 Tier 3 Tier 4 Tier 50

50

100

150

200

250

300

350

400

Pipes

Large Culverts

Bridges

Roads Paral-leling Streams

District 1

Tier 1 Tier 2 Tier 3 Tier 4 Tier 50

50

100

150

200

250

300

350

400

Num

ber o

f Ass

ets

District 6

Facility Level Adaptation Assessments

1. Describe the site context2. Describe the facility3. Identify climate stressors

- Heavy precipitation

4. Develop climate scenarios (Low, Medium, High)5. Assess performance of the facility6. Identify adaptation options

– Meet MnDOT 50-year clearance guidance – Meet FEMA 100-yr floodplain impact regulations

7. Assess performance of the adaptation options8. Conduct an economic analysis9. Evaluate additional considerations10. Select a course of action11. Plan and conduct ongoing activities

Adaptation Assessment General Approach

US 63 Spring Valley Culvert 5722

Adaptation Analysis Case Study Example

• Culvert 5722• Crosses Spring Valley

Creek south of Rochester• Drainage Area: 14 mi2

• AADT 5,700• Detour: 0.6 miles• Floods at current 10 year

storm

District 6 – Spring Valley Creek

24-Hr Storm Return Period

Atlas 14

Precip. Depth

(in)

Low Scenario Precipitation Depth (in)

Medium Scenario Precipitation Depth (in)

High Scenario Precipitation Depth (in)

2040 2070 2100 2040 2070 2100 2040 2070 2100

2-yr storm 2.79 2.80 2.81 2.81 2.94 3.04 3.15 3.01 3.21 3.46

5-yr storm 3.7 3.72 3.73 3.73 3.87 3.98 4.09 4.14 4.61 5.11

10-yr storm 4.49 4.52 4.53 4.54 4.68 4.81 4.95 5.30 6.16 7.07

25-yr storm 5.69 5.73 5.76 5.77 5.94 6.10 6.27 6.93 8.24 9.66

50-yr storm 6.7 6.76 6.79 6.81 7.00 7.20 7.41 8.22 9.83 11.61

100-yr storm 7.81 7.90 7.94 7.96 8.18 8.43 8.69 9.58 11.45 13.59

500-yr storm 10.8 10.97 11.05 11.10 11.40 11.80 12.23 12.96 15.33 18.25

Projected Climate Conditions

Adaptation Options: Culvert 5722

• Base: Replace in-kind– Construct cost: $460,000

• Option 1: Add 2 6’x10’ culvert cells to existing design– Construction cost: $690,000

• Option 2: same as option 1 + floodplain enhancement– Construction cost: $1,130,000

• Option 3: Replace Culvert three span 84-foot long bridge– Construction cost: $4,210,000

COAST Model

Option 1 Construction Cost

1267 1268 1269 1270 1271 1272 1273 1274 1275$0

$50,000$100,000$150,000$200,000$250,000$300,000$350,000$400,000$450,000$500,000

Option 1 Depth Damage Function

With Social Costs Without Social CostsDepth

0.1% 1.0% 10.0% 100.0%1266.001267.001268.001269.001270.001271.001272.001273.001274.001275.00

Option 1 Depth Probabilities (2025-2055)D

epth

0.1% 1.0% 10.0% 100.0%1266.001267.001268.001269.001270.001271.001272.001273.001274.001275.00

2056-2085

Dep

th

0.1% 1.0% 10.0% 100.0%1267.001268.001269.001270.001271.001272.001273.001274.001275.00

2086-2100

Low Scenario Medium Scenario High Scenario

Dep

th

Cost Effectiveness: Culvert 5722Without Social Costs With Social Costs

Base case Option 1 Option 2 Option 30

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

3,500,000

4,000,000

Low Med High

Cum

ulati

ve C

ost (

Pres

ent V

alue

)

Base case Option 1 Option 2 Option 3$0

$500,000

$1,000,000

$1,500,000

$2,000,000

$2,500,000

$3,000,000

$3,500,000

$4,000,000

Low Med High

Social costs include safety and detour costsDiscount Rate: 2.0%

Conceptual Adaptation Screening Framework

Lessons Learned

• Data availability/accuracy/consistency• System-level screen is possible• Build more time for variable weight discussion/

sensitivity analysis• Adaptive capacity needs more discussion• Adaptation doesn’t have to be scary – might be

more incremental

Next Steps

– Complete assessments in other districts and/or other types of “assets” (i.e. slopes)

– Explore partnerships with floodplain managers to develop real-time monitoring and warning systems for tier 1 and 2 assets

– Incorporate considerations of risk into ongoing culvert and bridge improvement programs

– Incorporate scores into asset management databases and the asset management plan

QUESTIONS?

www.mndot.gov/climate

Project Contact:Philip SchaffnerPolicy Planning DirectorMnDOT Office of Transportation System Managementphilip.schaffner@state.mn.us651-366-3743