Economics of Green Infrastructure in Adapting to Extreme Precipitation

Transcription

1 Economics of Green Infrastructure in Adapting to Extreme Precipitation ERG: Arleen O Donnell, Tess Forsell, Lauren Scott Horsley Witten Group: Nate Kelly and Kathleen McAllister NOAA Coastal Services Center Association of State Floodplain Managers Army Corps of Engineers, Institute of Water Resources Communities of Toledo Ohio and Duluth, MN Minnesota Sea Grant American Rivers

2 Great Lake Pilot Projects: Duluth and Toledo Duluth, MN Toledo, OH Duluth - damages from rarer, high intensity events Toledo - damages from frequent, low intensity events

3 Trends in the Great Lakes Experiencing precipitation more as rain, less as snow Projecting more intense precipitation in short durations, with extended periods of drought 3

4 Sidewalk Superintendent Assessing Damages

5 After the Sun Comes Out $55 million in costs for approximately 700 repair jobs from one storm event in 2012

6 We can t afford to keep doing this

7 Communities interested in using green infrastructure to help reduce flooding, but need to know What are the options? What do they cost? What benefits do they provide? 7

8 Project Objectives Identify green infrastructure flood reduction options and the costs and benefits of these options Create an approach to inform decisions about future infrastructure investments 8

9 HOW MODELS WERE USED CREAT Historical climate data Projected climate data H&H Peak flow Runoff volume Base flood elevation HAZUS Flood damage costs

10 Scenarios: Estimate Flood Losses 1. How much rain? Historical Future 2. How much runoff? 3. Estimate flood 4. Losses damages = $ Damages to buildings, infrastructure, recreation, land Current land use Future land use

11 Scenarios: Estimate Flood Reduction 1. Rain 2. How much runoff with green infrastructure? 3. Estimate flood damages to buildings Historical Future 4. Estimate costs & benefits Costs = green infrastructure implementation and maintenance ($) Benefits = reduced damages ($) $

12 Benefit of this happening less?

13 Benefit of less homes damaged?

14 Benefit of being able to use the park?

15 enefit of not having to fix damaged land?

16 What Did the Modeling Show Us? The probability that Duluth will experience damage from 100 year storm events will nearly double based on future growth (increased runoff) and future precipitation in 20 years Next Question: How can green infrastructure help reduce damage?

17 Our Approach to Assessing GI GI Options What are the feasible GI options for the watershed? Overall Storage What is the amount of storage desired to reduce flooding? Change in Flooding GI Cost How does flooding change if the desired GI storage is implemented? What would it cost to get the storage we need using different types of GI?

18 Target: reduce peak discharge by DULUTH 20%

19 How much green infrastructure storage is needed to reach this target? 76 acre-feet (current conditions) 86 acre-feet (future conditions)

20 Green Infrastructure

21 GI Options Permeable/porous pavement Blue roof Retention pond Stormwater tree trench Bioretention Extended detention wetland Underground storage Green roof

22 What and how much of each?

23 GI Unit Costs Green Infrastructure Practice Capital Cost per Square Foot ($/SF) Capital Cost per Cubic Foot ($/CF) Annual O&M Cost per Square Foot ($/SF/year) Annual O&M Cost per Cubic Foot ($/CF/year) Bioretention Blue Roof N/A Permeable Pavement (sidewalk) Underground Storage Stormwater Tree Trench N/A N/A 41.3 N/A 1.3 7,500 per unit N/A N/A N/A Retention Pond Extended Detention Wetland N/A

24 GI Unit Costs Most Expensive $$$$ Least Expensive $ Capital Cost per Cubic Foot of Flood Storage Provided ($/CF) Underground Storage Bioretention Permeable Pavement Blue Roof Retention Pond Extended Detention Wetland

25 Hypothetical Cumulative Costs Green Infrastructure Practice Capital Cost per Cubic Foot ($/CF) Potential Storage Volume (CF) Estimated Cost (over 20 years) Bioretention ,000,000 $21,200,000 Blue Roof ,000 $900,000 Permeable Pavement (sidewalk) ,000 $840,000 Retention Pond 2.9 1,000,000 $2,900,000 Extended Detention Wetland TOTAL 1.3 1,100,000 $1,430,000 3,300,000 CF (75.8 acre-feet) $27,271,000

26 What are the Benefits?

27 Change in Flooding How does flooding change if the desired GI storage is implemented? Hazus estimated approximately: 38% fewer buildings damaged 27% monetary reduction in building damages

28 Benefits (Loss Reductions, over 20 years) Loss Type Benefits Structure Damage (Hazus) $1,011,887 Recreational Use $357,279 Land Restoration $290,208 Storm Sewer Infrastructure $136,640 Total $1,796,014

29 What We Did Not Estimate Co-Benefits of Green Infrastructure Increased property values Ecological benefits Improved water and air quality Comparison of Costs to Gray Infrastructure Reduced Damages to Public Infrastructure Roads, bridges, sidewalks, (recall $55 Million from one storm) Utilities (power, communications, water, wastewater)

30 Lessons Learned Develop site selection criteria in advance Adequate data sets, previous modeling, previous flooding damage costs) Need fuller assessment of benefits or GI will be shortchanged Examine economics over longer period of time Examine other methods (velocity reduction, stormwater runoff regulations) in combination with GI storage

31 Duluth Next Steps Longer timeframe to show benefits exceed costs Sequence GI to coincide with other capital projects for economies of scale/reduced marginal costs (using stormwater fees for implementation) Track local costs/benefits of GI implementation Assess changes to stormwater and land use policies to avoid future impacts Explore velocity-reduction options

32 Project Next Steps Develop user-friendly step-by-step process guide for others to use Try methodology in different geographies, with different climate issues and different climate impacts Try to quantify more benefits Adjust methodology accordingly

33 Questions?