coordinated solutions for floodplain management and risk ...• watershed-wide, structure-level...
TRANSCRIPT
![Page 1: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/1.jpg)
KC Urban Stormwater Conference
February 4, 2019
Coordinated Solutions for
Floodplain Management
and Risk Reduction
![Page 2: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/2.jpg)
Agenda
1. Project Background
2. Project Approach
3. Assumptions
4. Methodology
5. Results
![Page 3: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/3.jpg)
Project Background
![Page 4: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/4.jpg)
Project BackgroundShort description or sentence can go here.
Sub title
•
•
•
More Tips
•
•
Walnut Creek Watershed
53,000-acre HUC 12 Watershed
![Page 5: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/5.jpg)
Project Background
Walnut Creek Watershed
53,000-acre HUC 12 Watershed
400+ acres developed annually
![Page 6: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/6.jpg)
Project Background
2,200 parcels impacted by floodplain
628 parcels in Clive impacted by floodplain
1% Steams banks are stable
57% Steams have moderate to severe erosion
![Page 7: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/7.jpg)
Project Background
• Goals:• Large Scale, Structure-Specific
Risk Assessment
• Evaluation of Current and Future
Flood Risk
• Mitigation Options
• Public engagement
Walnut Creek Mitigation Benefits
Estimator (MBE) Analysis
FEMA/STARR II
USACE
Walnut Creek WMA
![Page 8: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/8.jpg)
Mitigation Benefits Estimator
Mitigation Benefits Estimator (MBE)• Automate the FEMA Benefit-Cost Analysis
(BCA) Toolkit
• Analyze structure-specific risk (residential and
non-residential)
• Estimate benefits/costs for various mitigation
options
• Elevation
• Acquisition
• Basement In-Fill
![Page 9: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/9.jpg)
MBE Results
• Geodatabase
• Structure-specific results
• Flood risk
• Damages ($) – recurrence interval and
annualized
• Depth of flooding (ft)
• Mitigation Option Identification
• Cost and benefits
– Elevation
– Acquisition
– Basement fill-ins
![Page 10: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/10.jpg)
Project Approach
![Page 11: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/11.jpg)
Project Approach
• Phase I – Data Collection
• Stakeholder Group Formation
• Assumption Confirmation
• Phase II
• Flood Hazard Data Development
• Phase III
• MBE Assessment - Risk Assessment and
Mitigation Options Analysis
• Phase IV
• Reporting of Results
![Page 12: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/12.jpg)
Data Collection
Stantec USACE Local
Structure Data
Building Value n n
Building Footprints n
First Floor Elevation n n
Replacement Value n
Flood Data
Existing Conditions n
Future Conditions n
Depth Damage Functions
Residential n
Non-Residential n
Mitigation Option Information
Elevation n n
Acquisition n n
Basement In-Fill n
![Page 13: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/13.jpg)
Assumptions
![Page 14: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/14.jpg)
Building & Damage Assumptions
FFE
• Building replacement value
• Cost per square foot: Craftsman 2018 Nation
Building Cost Manual
• Building Content value
• 1.0 (100% of building replacement value) per
USACE residential and non-residential contend
depth damage functions
• First floor elevation (FFE)
• Where the FFE was unknown a highest adjacent
grade plus one foot was used.
• Depth damage functions
• USACE Economic Guidance Memorandum 04-017
![Page 15: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/15.jpg)
Flood Hazard Data Development
Walnut Creek at NW 100th Street
%Chance Exceedance Return Year
Existing Conditions Model (CFS)
FEMA Flood Insurance Study Discharges (CFS)
2018 USACE Future –Atlas 14 (cfs)
0.1 1000 35,660 41,400
0.2 500 23,280 23,245 35,300
0.5 200 18,410 28,000
1 100 16,600 16,570 23,000
2 50 13,410 13,340 18,400
4 25 10,450 14,400
10 10 7,110 7,105 9,900
20 5 4,990 7,000
![Page 16: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/16.jpg)
Mitigation Project
Assumptions
• Elevation
• Acquisition
• Basement Infill
![Page 17: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/17.jpg)
MBE Methodology & Analysis
![Page 18: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/18.jpg)
Methodology
Water Surface
ElevationsFlood Depth
Percent Damage
Losses ($)
Annualized Loss
($)
Project Benefits
&
Costs
($)
Mitigation Benefit Ratio
![Page 19: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/19.jpg)
Risk Assessment Methodology
• Methodology: based on FEMA’s BCA Toolkit (probabilistic)
• Probabilistic Damages – damages calculated at designated recurrence
intervals
![Page 20: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/20.jpg)
Analysis
![Page 21: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/21.jpg)
MBE Results
![Page 22: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/22.jpg)
Walnut Creek Watershed MBE Results
• 13,079 Total Properties Analyzed
• 787 Properties With Risk > $0
• $4.5m Annualized Risk Existing
Condition
• $11.6m Annualized Risk Future
Condition
• 75% Residential Properties
City NameStructures Analyzed
At Risk Structures
Clive 3,044 396
Dallas Center 21 --
Des Moines 1,442 60
Grimes 334 4
Johnston 47 --
Urbandale 5,224 120
Waukee 184 --
West Des Moines 1,881 16
Windsor Heights 868 179
Other 34 12
![Page 23: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/23.jpg)
City of Clive
100 Yr Approx
100 Yr Detailed
Floodway
500 Yr
![Page 24: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/24.jpg)
City of Clive Annualized Risk Assessment Values
100 Yr Approx
100 Yr Detailed
Floodway
500 Yr
$14k
$23,440k
![Page 25: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/25.jpg)
City of Clive Annualized Risk Assessment Values
100 Yr Approx
100 Yr Detailed
Floodway
500 Yr
$14k
$23,440k
![Page 26: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/26.jpg)
Acquisition – Mitigation Benefit Ratio
> 1.00 (Max 5.1)
0.75 – 1.00
0.50 – 0.75
0.25 – 0.50
< 0.25
MBR Values
Properties Costs Benefits MBR
26 $24m $35m > 0.75
17 $19m $31m > 1.00
![Page 27: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/27.jpg)
Elevation – Mitigation Benefit Ratio
MBR Values
> 1.00 (Max 8.7)
0.75 – 1.00
0.50 – 0.75
0.25 – 0.50
< 0.25
Properties Costs Benefits MBR
75 $15m $39m > 0.75
63 $8m $34m > 1.00
![Page 28: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/28.jpg)
Basement Fill – Mitigation Benefit Ratio
MBR Values
> 1.00 (Max 2.1)
0.75 – 1.00
0.50 – 0.75
0.25 – 0.50
< 0.25
Properties Costs Benefits MBR
7 $201k $231k > 0.75
4 $113k $154k > 1.00
![Page 29: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/29.jpg)
Specific Structure Example – NW 78th St, Clive
100 Yr Approx
100 Yr Detailed
Floodway
500 Yr
![Page 30: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/30.jpg)
Specific Structure Example – Building Information
Structure Information
First Floor Elevation 830.8 ft
Building Type/Use Residential
Building Replacement Value $88,783
Content Value $44,392
![Page 31: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/31.jpg)
Flood Damages ($) & Flood Depth – Pre Mitigation
Structure Damage Content Damages
Total Damages (structure +
Content) Flood Depth (ft)
5-year -- -- --
10-year $16,166 $5,342 $21,508 0.07
25-year $28,588 $7913 $36,501 3.06
50-year $43,466 $11,235 $54,701 6.42
100-year $88,783 $11,575 $100,358 6.91
200-year $88,783 $12,375 $101,158 7.49
500-year $88,783 $13,066 $101,849 8.13
1,000-year $88,783 $13,714 $102,497 8.69
Annualized Loss $3,504 $819 $4323 --
![Page 32: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/32.jpg)
Flood Damages ($) & Flood Depth – Pre Mitigation
Benefits Costs MBR
Acquisition
$87,000 $127,000 0.67
Elevation
$77,000 $49,000 1.58
Basement Fill
$34,000 $17,000 2.07
![Page 33: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/33.jpg)
Walnut Creek Watershed MBE Results
Existing Conditions
MBE Results
Future Conditions
MBE Results
Elevation Total Mitigation Cost
Needed (MBR>1.0)$10.6 million $32.2 million
Elevation Total Estimated Benefits
(MBR>1.0)$41.1 million $122.1 million
Acquisition Total Mitigation Cost
Needed (MBR>1.0)$20.4 million $38.7 million
Acquisition Total Estimated Benefits
(MBR>1.0)$34.4 million $96.8 million
Basement In-Fill Total Estimated
Benefits (MBR>1.0)$0.2 million $0.8 million
Basement In-Fill Total Estimated
Benefits (MBR>1.0)$0.3 million $1.5 million
![Page 34: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/34.jpg)
Walnut Creek Watershed MBE Benefits
• Watershed-wide, structure-level flood risk
assessment – existing and future
• Identification of financial resources necessary to
mitigate flood risk
• Consistent risk communication across
organizations
• Opportunity to incorporate results into local HMPs
• Organization of HMA grant application inputs
• Preliminary evaluation of mitigation projects
• Mechanism to prioritize funding
![Page 35: Coordinated Solutions for Floodplain Management and Risk ...• Watershed-wide, structure-level flood risk assessment –existing and future • Identification of financial resources](https://reader034.vdocuments.net/reader034/viewer/2022050509/5f9a673c6bf77b12424c8e5d/html5/thumbnails/35.jpg)
Questions