Florence, Kansas Flood Risk Management Options
September 2018 Final Report
USACE National Nonstructural Committee and USACE-Kansas City District in support of the Kansas Hazard Mitigation Team through USACE Silver Jackets Program
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Table of Contents Executive Summary ...... vii 1.0. Introduction ...... 1 1.1. Study Purpose ...... 1 1.2. Study Authority ...... 2 1.3. Study Team ...... 4 2.0. Identifying Flood Risks ...... 5 2.1. Study Area...... 5 2.2. Flood Sources ...... 5 2.3. Existing Flood Risk Management Measures ...... 6 3.0. Flood Risk Assessment ...... 7 3.1. Levee’s Risk Characterization Summary ...... 9 3.2. Risk Scenarios for Stakeholders...... 9 3.2.1. Primary Scenario ...... 10 3.2.2. Secondary Scenario ...... 13 3.2.3. Other Scenarios To Consider ...... 14 3.3. Risk Assessment Analysis and Evaluation ...... 14 3.4. Land Survey ...... 15 3.5. Flood Levels ...... 27 4.0. Flood Risk Management Menu of Measures ...... 38 4.1. Nonstructural Flood Risk Adaptive Measures ...... 39 4.2. Protecting Critical Facilities ...... 40 4.3. Common Nonstructural Flood Risk Adaptive Measures ...... 41 4.3.1. National Flood Insurance Program ...... 41 4.3.2. Floodplain Regulation and Floodplain Management ...... 42 4.3.3. Public Alert and Flood Warning ...... 42 4.3.4. Emergency Action Planning ...... 42 4.3.5. Evacuation Planning ...... 42 4.3.6. Flood Openings in Foundations ...... 43 4.3.7. Utility Service, Equipment, and Tanks ...... 44 4.3.8. Manufactured Homes ...... 44 4.3.9. Buyout with Demolition/Salvage of the Building ...... 44 4.3.10. Relocation of Building ...... 45 4.3.11. Removal of Basement ...... 45 4.3.12. Elevation of Building ...... 45 4.3.13. Dry Flood Proofing ...... 46 4.3.14. Wet Flood Proofing...... 47 4.3.15. Berms, Levees, and Floodwalls ...... 48 4.3.16. Land Use Regulation ...... 49 4.3.17. Beneficial Use ...... 49 4.4. Temporary Flood Risk Adaptive Measures ...... 49 4.4.1. Common Temporary Flood Risk Adaptive Measures...... 50
USACE-Kansas City District, Silver Jackets Program September 2018
4.4.2. Implementing Temporary Measures ...... 50 4.4.3. Flood Characteristics Dictating Temporary Measures ...... 52 4.4.4. Planning and Preparation of Temporary Measures ...... 52 5.0. Nonstructural Assessment Objectives ...... 57 5.1. Description of Assessment Inventory ...... 57 5.2. Description of Nonstructural Assessment ...... 58 6.0. Risk Management Options Recommendations ...... 60 6.1. Tier 1, Flood Risk Management Options for the Overall Community ...... 61 6.1.1. Tier 1, Flood Insurance ...... 61 6.1.2. Tier 1, Emergency Action Planning ...... 63 6.1.3. Tier 1, Flood Warning ...... 66 6.2. Tier 2, Flood Risk Management Options for the Property Owners ...... 67 6.3. Tier 2, Detailed Explanation of Risk Management Options ...... 82 6.3.1. Tier 2, Risk Management Options for Utilities ...... 82 6.3.2. Tier 2, Risk Management Options Using Flood Openings in Foundations ...... 82 6.3.3. Tier 2, Risk Management Option for Basement Flooding ...... 83 6.3.4. Tier 2, Risk Management Option for Nonresidential Structures with Basements ...... 85 6.3.5. Tier 2, Risk Management Option for Structures with Crawl Spaces ...... 87 6.3.6. Tier 2, Risk Management Option for Structures with Slab on Grade Foundations ...... 89 6.3.7. Tier 2, Risk Management Option, Relocation ...... 92 6.3.8. Tier 2, Risk Management Option, Buyouts ...... 92 6.3.9. Tier 2, Parametric Cost-Benefit Analysis of Nonstructural Risk Management Options ...... 92 6.4. Flood Risk Management Options for Critical Facilities and Public Property ...... 95 7.0. Suggested Risk Management Options for Floodplain Managers and Emergency Managers ...... 98 7.1. Emergency Action Plan ...... 98 7.2. Risk Communication ...... 98 7.2.1. Historic Flood Signage ...... 99 7.2.2. Annual Outreach To Property Owners in the Leveed Area ...... 99 7.3. Development Areas ...... 100 8.0. Combination Structural and Nonstructural Measures ...... 101 9.0. Conclusion and Next Steps ...... 103 Appendix A: Flood Risk Management Glossary ...... 106 Appendix B: Dry Flood Proofing Example ...... 117 Appendix C: Nonstructural Assessment Glossary ...... 123
List of Figures Figure 1-1. Local decisions on the best measures will define the mitigation actions...... 1 Figure 2-1. Regional map for Florence, Kansas...... 5 Figure 2-2. The Florence Hotel in 1906...... 6 Figure 3-1. Florence, KS flood insurance map (effective March 2011) shown with land survey points. .... 8 Figure 3-2. A cross section of Florence showing the levee with existing condition for past flood examples...... 10
USACE-Kansas City District, Silver Jackets Program September 2018
Figure 3-3. A cross section of Florence showing the Primary Scenario with the levee for the “natural valley” inundation...... 10 Figure 3-4. KDA Division of Water Resources proposed digital FIRM (May 2018)...... 12 Figure 3-5. A cross section of Florence showing the Secondary Scenario with the levee...... 13 Figure 3-6. The notification letter sent to property owners about the land survey...... 15 Figure 3-7. Land survey point labels (southwest Florence leveed area)...... 16 Figure 3-8. Land survey point labels (southwest Florence leveed area)...... 16 Figure 3-9. Land survey point labels (south Florence leveed area)...... 17 Figure 3-10. Land survey point labels (south Florence leveed area)...... 17 Figure 3-11. Land survey point labels (south Florence leveed area)...... 18 Figure 3-12. Land survey point labels (south Florence leveed area)...... 18 Figure 3-13. Land survey point labels (downtown Florence leveed area)...... 19 Figure 3-14. Land survey point labels (east Florence leveed area)...... 19 Figure 3-15. Land survey point labels (west Florence leveed area)...... 20 Figure 3-16. Land survey point labels (downtown Florence leveed area)...... 20 Figure 3-17. Land survey point labels (east Florence leveed area)...... 21 Figure 3-18. Land survey point labels (west Florence leveed area)...... 21 Figure 3-19. Land survey point labels (central Florence leveed area)...... 22 Figure 3-20. Land survey point labels (east Florence leveed area)...... 22 Figure 3-21. Land survey point labels (west Florence leveed area)...... 23 Figure 3-22. Land survey point labels (north central Florence leveed area)...... 23 Figure 3-23. Land survey point labels (east Florence leveed area)...... 24 Figure 3-24. Land survey point labels (northwest Florence leveed area)...... 24 Figure 3-25. Land survey point labels (north Florence leveed area)...... 25 Figure 3-26. Land survey point labels (north Florence leveed area)...... 25 Figure 3-27. Land survey point labels (north Florence leveed area)...... 26 Figure 3-28. Land survey point labels (northwest Florence leveed area)...... 26 Figure 3-29. Land survey point labels (north Florence leveed area)...... 27 Figure 4-1. Crawl space detail showing flood opening...... 43 Figure 4-2. A collapsed foundation from the Labor Day Flood in Manhattan, KS in 2018...... 43 Figure 4-3. Examples of typical air vents used as flood openings, where net open area varies...... 43 Figure 4-4. Building section of proposed mitigation: showing an elevated manufactured home, an elevated utility, and proper anchoring for the home as well as the tank...... 44 Figure 4-5. Elevation of Structure (Diagrammatic Section)...... 46 Figure 4-6. Dry Flood Proofing (Diagrammatic Detail)...... 47 Figure 4-7. Wet Flood Proofing (Diagrammatic Detail/Section) ...... 48 Figure 4-8. Berms, Levees, Floodwalls (Diagrammatic Detail)...... 48 Figure 6-1. In floodplains, the risk of flooding is five times greater than fire (ASCE, So, You Live Behind a Levee!)...... 62 Figure 6-2. Flood Insurance Premium Reduction through Elevation...... 63 Figure 6-3. USGS gage alerts come to any applicant for free using this subscription web site...... 66 Figure 6-4. The emergency managers can use forecasted stages from NOAA National Weather Service as a flood warning tool to take action per their emergency action plan...... 67 Figure 6-5. A Florence, Kansas property with the air conditioner already elevated...... 82 Figure 6-6. Existing condition building with a basement that floods...... 83 Figure 6-7. Example home in Florence with basement windows...... 83 Figure 6-8. Proposed risk management option: Elevation on foundation walls...... 84 Figure 6-9. Proposed risk management option: Wet flood proofing...... 84 Figure 6-10. Proposed risk management option: Dry flood proofing and fill basement...... 85 Figure 6-11. Existing nonresidential building with basement flooding...... 86
USACE-Kansas City District, Silver Jackets Program September 2018
Figure 6-12. Proposed risk management option: Dry flood proofing a nonresidential building with a basement...... 87 Figure 6-13. A home in Florence with a crawl space...... 87 Figure 6-14. Existing crawl space that floods...... 88 Figure 6-15. Proposed risk management option: Wet flood proofing a crawl space...... 88 Figure 6-16. A home with a slab on grade foundation in Florence, Kansas...... 89 Figure 6-17. Existing condition of flooding on a slab on grade building...... 90 Figure 6-18. Proposed risk management option: Elevating a building on fill...... 90 Figure 6-19. Proposed risk management option: Dry flood proofing...... 91 Figure 6-20. Proposed risk management option: Wet flood proofing...... 91 Figure 6-21. Proposed risk management option: Wet flood proofing in main floor addition...... 92 Figure 6-22. Candidate property for building relocation...... 93 Figure 6-23. Topographic map for Florence, Kansas...... 97 Figure 7-1. Flood categories on the gage, Cottonwood River Near Florence...... 98 Figure 7-2. A historic flood sign used to communicate the flood risk of high water in nearby Marion, Kansas (2018)...... 99 Figure 7-3. Example annual mailer for California communities (2017)...... 99 Figure 8-1. Levee interior drainage will pond at two locations (light blue shading) showing the limits for the 1% annual chance exceedance...... 101 Figure 8-2. Risk management options may be combined to address factors driving the risk (The Sponsor’s Guide To the USACE Levee Safety Program)...... 102
Figure B-1. Flooding at Example Building...... 118
Figure C-1. Closure/Shields...... 123 Figure C-2. Permanent Dry Flood Proofing...... 124 Figure C-3. Temporary Dry Flood Proofing...... 124 List of Tables Table 1-1. Study Team...... 4 Table 3-1. Risk Characteristics from the USACE National Levee Database...... 9 Table 3-2. Flood elevations for the Secondary Scenario in Florence, Kansas (USACE Tulsa District). ... 13 Table 3-3. Summary of Flood Risk Scenarios...... 14 Table 3-4. Property elevations and depths for the study area...... 28 Table 6-1. Tier 1 Recommended Priority Risk Management Options for All Scenarios and Broad Community Actions...... 61 Table 6-2. Tier 2 Recommended Risk Management Options for the Primary Scenario for Mitigation Actions at Specific Properties...... 64 Table 6-3. Planning level cost estimating for some risk management options ...... 93 Table 6-4. Example Cost of Annual Premiums for Flood Insurance in Florence...... 94 Table 6-5. List of Land Survey Point Numbers for Critical Facilities and Public Property...... 96 Table 9-1. A summary counting the nonstructural measures recommended as risk management options for buildings in Florence...... 104 Table 9-2. Community level cost estimate for implementing all the nonstructural measures for the buildings...... 105
USACE-Kansas City District, Silver Jackets Program September 2018
EXECUTIVE SUMMARY
The Kansas Department of Agriculture (KDA), Division of Water Resources requested the U.S. Army Corps of Engineers (USACE) Silver Jackets Program and the USACE National Nonstructural Committee help Marion County and the City of Florence, Kansas in identifying specific mitigation actions in and around their levee. Florence has a levee in good condition, although this report encourages the city and property owners to not depend only on the levee to address flooding. The levee reduces flood risk but does not eliminate it. Property owners can use the report to better understand that a diverse set of measures makes them resilient to The levee flooding. reduces flood The report provides an overview of the full menu of flood risk management measures and helps the city and property owners focus in on property level risk risk but does management options for 264 properties. The report provides recommendations on actions that will reduce the residual flood risk in the community. not eliminate The report aids the city and property owners in understanding possible it. economic impacts if the levee is not re-accredited under the FEMA National Flood Insurance Program (NFIP) in the latest Flood Insurance Rate Map (FIRM). The state and FEMA expect the city will have a professional engineer certify the levee. If the levee is not accredited, the economic impacts will be different for property owners. The flood risk does not depend on this, so the report provides perspective on the flood risk and what actions will help mitigate the flood risk. The flood risk is discussed using two scenarios. • Primary Scenario. Inundation based on the proposed digital FIRM. The May 2018 KDA Division of Water Resources proposed FEMA digital FIRM showing the “natural valley” inundation describes the risk for this scenario. • Secondary Scenario. This scenario describes flooding upon overtopping, as occurs in the 0.2% annual chance of exceedance (ACE) inundation. Property owners should diversify their flood risk management playbook, and at a minimum, each home and business should add at least one other floor risk reduction measure. The county, state, and federal floodplain leaders recommend they all get flood insurance. With an accredited levee, the community can benefit from lower flood insurance premiums, and with flood insurance, property owners will recover quicker and more whole. Unlike disaster assistance, which must be repaid as a low interest loan. Residents knowing more about risk of the chance of flooding, as described above, should take advantage of the lower premium and the added line of defense. This report recommends that more than one measure be part of the Florence flood risk management playbook, and the project team applied the Primary Scenario to individual properties. The most common recommended measure for property owners is to wet flood proof their building. In addition, 115 of the properties need flood openings, and 14 mobile homes or manufactured buildings, which are at risk of floating, need to be anchored properly to the ground. Under the Secondary Scenario, the project team gives recommendations on the critical infrastructure and the existing emergency action plan (EAP). The EAP is missing the entire section on the flood hazard, so the project team recommends enhancements, especially for the evacuation during flooding. Recommendations also note the city fire, ambulance, and emergency operations center should be relocated west and higher than Doyle Street. Also, the city will be more resilient if the water treatment structure is flood proofed to three feet above the ground. Finally, the use of flood warning, like getting automated stream gage notifications to key city staff for specific actions, will also improve the plan.
USACE-Kansas City District, Silver Jackets Program September 2018
1.0. Introduction The U.S. Army Corps of Engineers (USACE), Kansas City District (KCD), under the Silver Jackets Program funding, conducted this report at the Kansas Hazard Mitigation Team’s request for a nonstructural assessment to expand the understanding of most recommended flood risk management measures in Florence, Kansas. The report provides an overview of the full menu of flood risk management measures and helps the city and property owners focus in on property level risk management options specific to dealing with flood risks behind the levee. The City of Florence will decide on specific actions. This report will aid the city and the Marion County staff when helping property owners to better understand their flood risks, to better decide which actions to pursue, and to develop a plan that will allow the city to thrive in the future. This report is a product of the USACE Silver Jackets Program. The Kansas Hazard Mitigation Team co- leads in collaboration with the county, requested the assistance in 2016. In response to the fiscal year 2017 Call for Proposals for the Interagency Nonstructural Projects, USACE KCD, Kansas Department of Agriculture, Division of Water Resources (KDA DWR), and the Kansas Department of Emergency Management, jointly submitted a proposal. The USACE KCD based the proposal on a letter requesting assistance from KDA DWR on June 8, 2015 to perform a nonstructural assessment in Florence, and the letter indicated the city was unable to certify the levee at that time. The USACE Headquarters and Institute for Water Resources accepted the proposal, and the team began work in 2017. USACE KCD received the funding over a two year period. The Silver Jackets Program frequently taps knowledge, skills, and abilities from a variety of resources. This project benefits from USACE staff in • Kansas City District • Tulsa District • National Nonstructural Committee The Kansas state and local agencies have also provided significant technical services. • Kansas Hazard Mitigation Team • Kansas Department of Agriculture, Division of Water Resources • Marion County, Planning and Zoning
1.1. Study Purpose
This project is uniquely setup as a planning process that will identify the risk management options available to communities and the property owners located behind the levee. The work of the project is represented in Figure 3-1, which shows the process of narrowing the broader flood risk management measures down to very specific actions for a community that has a levee. Similar communities that are also levee sponsors in the USACE program should be mindful of their risk management options. After identifying the options, this planning process helps the community, the county, and the region Figure 1-1. Local decisions on the best measures to strategically prioritize the activities and the will define the mitigation actions.
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features that they need to fund in the future. Because these are often costly, the specific actions can be assigned to the appropriate party and scheduled. A solid understanding of who has the role, whether the city or the property owner, can be clearly explained. These strategic planning efforts can be captured in their local hazard mitigation plan, the state hazard mitigation plan, and any other playbook for flood risk management that seeks to do sustained flood mitigation. The hazard mitigation plans are required for FEMA disaster assistance, as relates to the Stafford Act of 2000. The risk management options, selected by the city and the property owners, are the flood risk mitigation actions that are pursued and knocked out over time. A combination of federal programs can assist with these flood mitigation actions. FEMA provides mitigation grants through several This document will be programs. HUD also offers possible assistance. Having a flood risk a valuable reference management playbook in advance of available funding for those for long-term flood programs will keep the community near the front of the list for those mitigation. opportunities. USACE recently provided a resource for combining structural and nonstructural features for levee sponsors in the USACE levee program, but also for floodplain leaders across the United States. This new resource, The Sponsor’s Guide To the USACE Levee Safety Program (EP 1105-1-1, June 2018), is very helpful in achieving the goal of mitigating flood risks. This project further supports the state and federal partners in addressing important principles behind flood risk mitigation. From the USACE Institute for Water Resources (IWR) October 2010 report (Exploration of Tolerable Risk Guidelines for the USACE Levee Safety Program, IWR report 10-R-8):
USACE is embracing tolerable risk in a risk-informed decision framework, and working within the concept of shared responsibility and accountability. These are concepts worthy of national implementation and USACE has an obligation to assist in making this happen. From Congress, in the 2014 act, a National Levee Safety Act (Title IX, of the Water Resources Reform and Development Act 2014) include these purposes: …to ensure that human lives and property that are protected by new and existing levees are safe; …to build public awareness of the residual risks associated with living in levee protected areas; …to develop technical assistance materials, seminars, and guidelines to improve the security of levees… The USACE districts, and their Silver Jackets Program staff, hope that this report aids the community and the state in accomplishing the actions in their flood hazard mitigation planning work.
1.2. Study Authority
The Silver Jackets Program uses a variety of authorities to supplement the state lead on flood risk management. USACE has extensive resources and authority available to support flood risk management. The technical services for this report are provided through the following authorities. • USACE Flood Plain Management Program (FPMS). Authorized by Section 206 of the Flood Control Act of 1960, as amended (33 U.S. Code § 709a), FPMS is sometimes referred to as the “Section 206” program. Under the FPMS Program, the USACE is authorized to compile and disseminate information on floods and flood damages, including identification of areas subject to inundation by floods of various magnitudes and frequencies, and general criteria for guidance of
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federal and non-federal interests and agencies in the use of floodplain areas; and to provide advice to other federal agencies and local interests for their use in planning to ameliorate the flood hazard. Floodplain management services cover the full range of information, technical services, and planning guidance and assistance on floods and floodplain issues within the broad umbrella of floodplain management. Technical services and planning guidance under the FPMS Program are provided to state, regional, and local governments without charge, within program funding limits. FPMS services for federal agencies and private persons are on a cost-recovery or fee basis. The Corps may also accept voluntarily contributed funds to expand the scope of services requested.
Common FPMS activities include:
o developing studies or guidance on floodplain delineation, o flood hazard evaluation, o hurricane evacuation, o flood warning/preparedness, o regulatory floodway analysis, o comprehensive floodplain management, o flood risk reduction, o urbanization impacts, o storm water management, o flood proofing, and o inventory of flood-prone buildings. The program also provides assistance for conducting workshops and seminars on nonstructural floodplain management measures such as flood proofing. • USACE Emergency Management (EM). EM leads USACE efforts to prepare for natural disasters, support communities in responding to flood events, and coordinate the repair of eligible flood risk management projects damaged by a flood. Federally declared disasters are governed by the Stafford Act, National Response Framework (NRF), and the National Disaster Recovery Framework (NDRF). These documents designate USACE as the lead federal agency for Public Works, Engineering, and Infrastructure System support that is provided to impacted states when missions are assigned by FEMA. These missions can include response and recovery missions for floods that are beyond USA CE Public Law (PL) 84-99 authority/policy. Flood Risk Managers and Silver Jacket Coordinators can assist Emergency Management personnel in states' and other federal agencies' preparation for all natural disasters, response, and recovery to flood events under PL 84-99 (Flood Control-Coastal Emergency appropriation) and NRF/NDRF, and support other elements of the flood risk management life-cycle. • Other USACE programs and authorities also support the Silver Jackets Program.
o General Investigations o Planning Assistance To States
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1.3. Study Team
The project has involved staff across a variety of organizations. The project team includes federal, state, and local partners. The USACE study team is a subset of the project team. The table below presents the partnering organization names and the titles of the roles participating, and the table shows the primary project team members with a “*” or asterisk symbol next to the roles conducting the project work.
Table 1-1. Study Team. Organization Title Organization Title
Kansas Department of State Floodplain USACE-Kansas City Lead Silver Jackets Agriculture, Division of Manager / NFIP District Coordinator* Water Resources Coordinator
Kansas Department of Floodplain Mapping USACE-Kansas City Land Surveyor* Agriculture, Division of Coordinator District Water Resources
Kansas Department of Contractor, Hydrologist USACE-Tulsa District Hydrologist and Agriculture, Division of and Hydraulic Engineer Hydraulic Engineer* Water Resources
Kansas Department of State Hazard Mitigation USACE-Tulsa District Levee Safety Program Emergency Officer Manager Management
Marion County, Kansas Planning and Zoning USACE-Tulsa District Geospatial Analyst* Lead
Florence, Kansas Floodplain USACE-National Plan Formulator* Administrator, City Nonstructural Clerk Committee
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2.0. Identifying Flood Risks
2.1. Study Area
Florence, Kansas is located in the heart of the Flint Hills in east central Kansas. The Census Bureau showed a population of 597 in 2009, and declining to 443 in 2015. The community ranks 293 out of 669 Kansas cities in 2017.
Figure 2-1. Regional map for Florence, Kansas.
Founded in 1870, the town benefited economically from a few events. The Atchison-Topeka & Santa Fe railroad was the lifeblood of the town for years. Oil booms helped the town in the 1880s and later in 1918. The city lies in the south central part of Marion County. Two main highways meet on the northwest side, including U.S. 50 and U.S. 77.
2.2. Flood Sources
The city is located at the confluence of the Cottonwood River and Doyle Creek in a lowland valley, which makes floods an ever present danger. The river flows from the northwest to the east. Doyle Creek hugs the south side of Florence. The first records show a flood occurred in 1877. The flood in 1903 was severe with water in the east side between three and five feet deep. In 1906, floods reached one to three feet in the downtown area and up to
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six feet on the east side. The railroad bridges and tracks were destroyed by the floodwater scouring while loaded with rail cars of coal. The 1951 flood was the most devastating. In July 1951 flood inundated most of Florence with some depths exceeding eight feet as the Cottonwood River crested at 37 feet. The community lost the library, two businesses, and a couple of homes that were washed off their foundations. While no lives were lost, The Kansas Governor declared Florence a natural disaster and sent in the National Guard.
2.3. Existing Flood Risk Management Figure 2-2. The Florence Hotel in 1906. Measures
The community has a number of measures in place to manage flood risks. Measures are defined as either a feature or management activity. An obvious feature is the Florence levee. Among the measures considered to be activities are the city’s efforts under the National Flood Insurance Program. Another ongoing activity is the operation and maintenance of a levee. The city is in the National Flood Insurance Program (NFIP). This program allows the public to get flood insurance. Flood insurance is not part of home owner insurance. Home owners in any part of the city may get the flood insurance, as the city maintains eligibility in the program. The FEMA NFIP has an organized incentive program, called the Community Flood Rating System (CRS), which encourages activities FEMA and federal partners insurance is consider best practices, and the city is participating, as noted on the state’s CRS not part of web page (http://agriculture.ks.gov/divisions- home owner programs/dwr/floodplain/NFIP/CRS). This means the city conducts additional activities outside the normal NFIP requirements to further reduce the risk of insurance. flooding. Each activity is incentivized with a point scale. The more points scored, the greater flood insurance premium reduction that all properties in the city can receive from FEMA’s flood insurance program. The levee is in the USACE levee program (P.L. 84-99). USACE started building the levee in December 1959 and finished administrative work in November 1964. Complete information on the levee is maintained on the National Levee Database (NLD). The web site is https://levees.sec.usace.army.mil/. The NLD provides the following description (as of August 2018):
The Florence Cottonwood River Levee is an approximately 1.6 mile long and 12 feet high, earthen levee along both the Cottonwood River and Doyle Creek in the City of Florence, Marion County, Kansas. The levee was constructed by the U.S. Army Corps of Engineers and upon completion in 1962 ownership was transferred to the City of Florence, Kansas for continued operations, maintenance, repair, rehabilitation, and replacement actions. Approximately 450 people live behind the levee and approximately 240 structures would be flooded during a flood event. An estimated $45 million dollars in property damage could occur during a large flood. The levee has been loaded during three separate floods; the largest flood (November 1998) reached about 35% of the levee’s height. The other two loading occurred in May 1993 and June 1975 had loading of 27% and 28%, respectively. The levee was designed for a 200-year flood event frequency, however the levee is built to a 500-year flood event frequency.
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3.0. Flood Risk Assessment The objective of this flood risk assessment is to identify the nature of the risk, the probability, and the consequences in a qualitative way. The identified risks for each property has a unique opportunity for potential risk management options. For Florence, the identification of flood risks should remind the community of the historic floods (see photograph in section Flood Sources) where without a levee, properties could be significantly impacted. Flood risk can be described by several factors. • Inundation and depth, Singling out flood • Velocity, events has a way • Proximity of the population / consequences, and of creating • Rate of rise. complacency and The inundation and depth, velocity, proximity of the population / consequences, and rate of rise are all ways to explain flood risk to presumed the public. This assessment focuses solely on flood inundation. safety… Flooding is made up of a continuum of events, however inundation maps that show areas flooded for a single event are very common. Singling out flood events has a way of creating complacency and presumed safety, when in reality a range of events will eventually happen. With a levee involved, the flood risk is further complicated by how the levee performs. The City of Florence’s flood risk can be partially described with the area of inundation shown in the FEMA Flood Insurance Rate Map (FIRM). This section of the report shows the FIRM for the map effective in March of 2011. The flood insurance map shows the special flood hazard area, also called the base flood, which presents one probable flood event with a 1 in 100 chance of occurring in any given year, or 1% annual chance of exceedance. Over the course of a 30-year mortgage, the risk of the levee for a 1% event is 26%, or a 1 in 4 chance while living at that address. The map in this section shows an aerial photo with the base flood in light blue. The Florence levee centerline is the dark purple line. As part of this project, the USACE Kansas City District conducted a land survey of the city in August of 2017. The area behind the levee shows the land survey points. The FIRM reflects the leveed area with a special bar hatched coloring. The flood risk is partially described, and limited as a description of flooding for several reasons. One element to consider is the more severe flood events and their associated frequencies. Another element to consider is how often a flood inundation map is updated. The recorded rainfall and stream gage records can only offer a snapshot in time for a particular frequency, since the maps, such as the FIRMs, are based on a particular period of time. For these reasons, the inundation maps only offer one perspective. The city, county, and state floodplain managers can offer a more detailed explanation.
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Figure 3-1. Florence, KS flood insurance map (effective March 2011) shown with land survey points.
Flood risks and the decisions about managing the flood risks with risk management options depend on some specific definitions. The IWR October 2010 report mentioned in the Introduction (Exploration of Tolerable Risk Guidelines for the USACE Levee Safety Program, IWR report 10-R-8) provides helpful insights (bold text, indentions, and formatting added for readability):
Risk is the probability that someone, or a thing that is valued, will be adversely affected by the hazard in a stipulated way.
Tolerability of risk is essentially a process for reaching decisions that reaches out for and involves stakeholders in its operation. Embedded in the process are criteria for deciding what risks are unacceptable, tolerable or broadly acceptable that mimics the way that people make decisions in their everyday life.
Tolerable risks are:
• risks that society is willing to live with so as to secure certain benefits;
• risks that society does not regard as … something it might ignore;
• risks that society is confident are being properly managed by the owner;
• and risks that the owner keeps under review and reduces still further if and as practicable.
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While the levee is owned by the city, the property owners share the responsibility of managing flood risks. Because tolerable risk is a decision shared by property owners and the general public, the various measures selected on a property by property basis will be unique. To assist all stakeholders, this report provides the flood risk assessment, specifically at their property, and later adds discussion on flood risk mitigation measures (section, Measures for Risk Mitigation).
3.1. Levee’s Risk Characterization Summary
While the City of Florence has a significant flood risk management measure in the levee, the public should fully understand the risks with the levee and that a diversity of measures is better than one single measure. The public should not rely on a single measure. From the USACE National Levee Database, the following risk characterization is available.
The Florence Cottonwood River Levee is considered to be low risk but the Corps identified the following risk factors: 1). Potential for overtopping is always a risk driver though this would require substantial rainfall, so far unseen at this project.
Residents behind the levee understand its role and limitations in flood risk reduction; and the community maintains a reverse 911 system, radio, sirens and door-to-door emergency warning systems to alert the community during an emergency event. Furthermore, the USACE National Levee Database also points out these facts.
Table 3-1. Risk Characteristics from the USACE National Levee Database. People at Risk 454
Structures at Risk 241
Property Value $45.1 million
3.2. Risk Scenarios for Stakeholders
The goal of providing risk scenarios is to help focus in on some findings that a property owner may find the most relevant when making decisions, especially in the context of a community using a … scenarios that levee. Flood risks have uncertainty in many of the variables used to analyze and evaluate risk management options. Floodplains help property have a continuum of flood elevations with different probabilities. owners And, levees can perform in a variety of ways when overtopped, including overtopping without a breach, overtopping with a understand the breach, and falling subject to seepage to the leveed area prior to overtopping. This section provides a discussion on a couple of limitations of their scenarios that help property owners understand the limitations of levees ability to their levee’s ability to reduce flood risks. The goal, similar to the city staff’s, is to mitigate for the inundation. reduce flood risks This risk assessment identifies two inundation scenarios for understanding the flood risk in Florence and for helping property owners determine their tolerable risk. At the time this report is written, the city is reviewing the proposed FEMA Flood Insurance Rate Map
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(FIRM) and how to address the inundation area for the unaccredited levee. The first scenario is based on the proposed flood insurance map. The second scenario is based on a USACE determined overtopping of the levee. Each property owner should consider these two flooding scenarios.
Figure 3-2. A cross section of Florence showing the levee with existing condition for past flood examples.
3.2.1. Primary Scenario This scenario is about flooding prior to overtopping. This inundation scenario is based on the results in the proposed digital FIRM. In May 2018, the KDA Division of Water Resources presented updated engineering results that are the basis of the flood risk in the primary scenario. These results will propose a FEMA digital FIRM showing the “natural valley” inundation of Florence (see figure below) and showing a similar area to the 2011 inundation area with improved resolution on the western edge. In the May meeting the city notified the state and FEMA of the intent to accredit the levee, which will allow FEMA to remove the special flood hazard area that the Division of Water Resources showed in the leveed area. The proposed digital FIRM results explain that without the levee, the base flood or (1% annual chance of exceedance) event could
Figure 3-3. A cross section of Florence showing the Primary Scenario with the levee for the “natural valley” inundation.
10 | Page USACE-Kansas City District, Silver Jackets Program September 2018 reach elevation 1272.2 for the location of 5th Street and Main Street (reference the cross section with elevation 1272.19 in Figure 3-4). The city’s official notice to the state and FEMA allows the leveed area to be shown as preventing the base flood from entering the leveed area, and this is known as a Provisionally Accredited Levee (PAL). A PAL has a defined period during which the city will get a professional engineer to certify the levee, and that certification will allow the FIRM to officially reflect that the base flood is kept outside the levee.
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Figure 3-4. KDA Division of Water Resources proposed digital FIRM (May 2018).
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3.2.2. Secondary Scenario This scenario is about flooding upon overtopping of the levee. As part of this Silver Jackets project, USACE Tulsa District conducted hydrologic and hydraulic engineering analysis for the Florence leveed area (Interior Flooding Analysis Florence Levee, June 2018). The hydrology uses the latest rainfall depths (NOAA Atlas 14). Hydraulic analysis uses models for the area to determine resulting flood elevations in the community. Considerations included the ability of the city to drain during a flash flood on the interior side of the levee, a flood on the Cottonwood River, and a coincident analysis of these two events. The analysis found the 1% annual chance of exceedance, or 100-year, inundation is driven by an interior storm and will be confined to the ponding areas. The 0.2% annual chance of exceedance (ACE) inundation is an overtopping event from the Cottonwood River, and the elevation will be approximately the same as the levee crest elevation. Continuing the example used earlier, a 30-year mortgage, a flood due to the 0.2% event ACE on the interior side of the levee has a chance of 6%, or more than a 1 in 20 chance, every year. A couple of low spots on the profile of the levee are at 1277.5 and are located just south of 4th Street.
Figure 3-5. A cross section of Florence showing the Secondary Scenario with the levee.
Table 3-2. Flood elevations for the Secondary Scenario in Florence, Kansas (USACE Tulsa District).
Event Elevation (% annual chance of exceedance) (feet above sea level)
10.0% [10-year] 1260.5
5.0% [20-year] 1261.1
2.0% [50-year] 1261.9
1.0% [100-year] 1262.5
0.5% [200-year] 1263.0
0.2% [500-year] 1277.5
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3.2.3. Other Scenarios To Consider While stakeholders may find this information overwhelming, other factors should be considered when assessing flood risks. As mentioned before, flood risk can be described with • Inundation and depth, • Velocity, • Proximity of the population / consequences, and • Rate of rise. Stakeholders in leveed areas often see the river as their only threat, but two other flood sources are important to understand. First, overland flow can affect any building. This could be floodwaters that pond next to a building and simply cannot go anywhere but into the building. This is a situation that does not depend on whether or not a levee is in the community. Secondly, for those property owners that do have a levee, they need to remember that the leveed area may also see rain, which means that rain will need to eventually pass through, over, or under the levee. That may require simple pipes that allow stormwater to flow one way to the river, temporarily holding that water to the river high water recedes. In some communities, pump stations are necessary. Another aspect is the risk of increasing rainfall intensities. In the document, USACE Climate Adaptation Plan (July 2014), USACE has recognized a potential vulnerability due to changing precipitation, specifically “more intense flooding over most of the U.S., but especially in the Midwest…”, and therefore, the USACE-Kansas City District is helping levee sponsors and communities like Florence, Kansas to develop, sort, and prioritize mitigation measures to reduce flood risk behind their levees. Another consideration is how rising global temperatures are impacting assumptions about rainfall. More intense precipitation is being seen more frequently, because a great amount of moisture is held in a warmer atmosphere.
3.3. Risk Assessment Analysis and Evaluation
The stakeholders may use the two scenarios to establish an understanding of the continuum of flood risk elevations affecting their properties. Residences and businesses may find that the Primary Scenario, the elevation for the proposed digital FIRM, to be a reasonable data point to establish their own playbook for flood mitigation actions. For critical facilities in the city, like the water treatment plant and the city offices, the Secondary Scenario, which is a 0.2% event, or 500-year, overtopping event, is important. Elevations for each scenario are provided in the table below. Table 3-3. Summary of Flood Risk Scenarios.
Name of Scenario Target Elevation
Primary 1272.2
Secondary 1277.5
While these specific numbers, the scenarios’ Target Elevations, help the reader focus on one particular risk, the project team cautions that the risks are a blend or continuum of the possible flood levels. Each property owner and the city will have their own conclusion of what their individual tolerable risk is, based on their own circumstances.
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3.4. Land Survey
The land survey points for properties in the lowest parts of the river valley are presented in this section. The USACE Kansas City District conducted a very limited land survey in August of 2017, as coordinated with the city and county and a mailer sent to property owners. Limited land surveys do not include attributes such as tree locations, curbs, storm sewer, or any other utilities. The land survey collected these elevations for 264 buildings. This elevation data helps during the assessment of measures or plan formulation when determining if a specific measure is more suitable than another, such as a Dry Flood Proofing measure’s three-foot maximum height threshold versus a decision to go with Elevating Building. The results of the land survey are presented in 23 figures in this section. The approach the land surveyors used was to collect the lowest adjacent grade and the finished floor elevation for the main, occupied building. This normally was the building with the mailing address, although many properties also have additional buildings that land surveyors collected data. In each of the figures the points are presented with numbers and lettering. The numbers correspond to the recommended risk management options in the section, Measures for Risk Mitigation. Each point has a prefix, FL-, for Florence. Occasionally, the land surveyor used trailing letters with each number to help Figure 3-6. The notification letter sent to property identify minor buildings also on the owners about the land survey. property besides the main building. On occasion, the land surveyor designated some points as unused. The figures present the land survey points in a particular order within the leveed area. The beginning point numbers are in the southwest of Florence. All figures have the same scale. Generally, the order goes from right to left, or west to east, and they move by block.
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Figure 3-7. Land survey point labels (southwest Florence leveed area).
Figure 3-8. Land survey point labels (southwest Florence leveed area).
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Figure 3-9. Land survey point labels (south Florence leveed area).
Figure 3-10. Land survey point labels (south Florence leveed area).
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Figure 3-11. Land survey point labels (south Florence leveed area).
Figure 3-12. Land survey point labels (south Florence leveed area).
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Figure 3-13. Land survey point labels (downtown Florence leveed area).
Figure 3-14. Land survey point labels (east Florence leveed area).
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Figure 3-15. Land survey point labels (west Florence leveed area).
Figure 3-16. Land survey point labels (downtown Florence leveed area).
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Figure 3-17. Land survey point labels (east Florence leveed area).
Figure 3-18. Land survey point labels (west Florence leveed area).
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Figure 3-19. Land survey point labels (central Florence leveed area).
Figure 3-20. Land survey point labels (east Florence leveed area).
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Figure 3-21. Land survey point labels (west Florence leveed area).
Figure 3-22. Land survey point labels (north central Florence leveed area).
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Figure 3-23. Land survey point labels (east Florence leveed area).
Figure 3-24. Land survey point labels (northwest Florence leveed area).
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Figure 3-25. Land survey point labels (north Florence leveed area).
Figure 3-26. Land survey point labels (north Florence leveed area).
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Figure 3-27. Land survey point labels (north Florence leveed area).
Figure 3-28. Land survey point labels (northwest Florence leveed area).
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Figure 3-29. Land survey point labels (north Florence leveed area).
3.5. Flood Levels
The flood levels from the latest flood map are presented in the tables below. This information ties the risk scenarios to each property. The city and property owners may use this information to decide the next steps in managing the flood risk with more specific measures. Points where the land surveyor did not use the number are designated as unused points. The Primary Scenario flood water level would reach 1,272.19 feet as compared to the land survey average 1,271.9 foot finished floor elevation. The flood depth is 1.1 feet above most finished floors and affects numerous basements. The Secondary Scenario water overtops the levee during a 0.2% (500 year) probability flood. Considerably more severe events impact critical infrastructure. The water depth would be over the height of most people at the city offices on Main Street. The Secondary Scenario flood, which would be rare, but much more devastating, requires attention on risks and actions related to critical infrastructure. These scenarios may be addressed if local and property level action is taken on the risk management options identified in the next section.
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Table 3-4. Property elevations and depths for the study area. ID# Address First Floor Ground Flood Depth on Adjacent Ground Elevation Elevation for Primary Scenario (feet) 1 101 DOYLE 1272.71 1270.61 1.6 2 110 DOYLE 1270.10 1269.70 2.5 3 Railroad Depot 1272.12 1271.61 -0.1 4 311 W 2ND 1270.43 1269.37 2.8 5 304 W 2ND 1271.08 1269.77 2.4 6 236 W 2ND 1270.36 1269.67 2.5 7 222 W 2ND 1271.52 1269.63 2.6
8 212 W 2ND 0.00 0.00 9 311 W 2ND 1271.69 1269.48 2.7 10 311 W 2ND 1270.01 1269.11 3.1 11 223 W 2ND 1273.49 1269.40 2.8 12 213 W 2ND 1270.71 1269.93 2.3 13 310 W 3RD 1269.69 1269.41 2.8 14 302 W 3RD 1272.19 1269.77 2.4 15 218 W 3RD 1270.20 1269.80 2.4 16 214 W 3RD 1270.96 1269.82 2.4 17 234 MARION 1270.76 1269.44 2.8 18 223 MAIN 1269.99 1268.65 3.5
19 103 E 3RD 0.00 0.00 20 302 MAIN 1270.81 1268.73 3.5 21 323 W 3RD 1273.65 1270.60 1.6 22 301 DOYLE 1272.04 1270.14 2.0 23 229 W 3RD 1271.80 1269.36 2.8 24 229 W 3RD 0.00 1269.11 3.1 25 209 W 3RD 1269.52 1269.47 2.7 26 201 W 3RD 1270.40 1269.26 2.9 27 308 MAIN 1270.15 1268.58 3.6 28 304 MAIN 1269.67 1268.64 3.6 29 129 W 3RD 1269.58 1269.30 2.9 30 125 W 3RD 1272.07 1268.84 3.4
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ID# Address First Floor Ground Flood Depth on Adjacent Ground Elevation Elevation for Primary Scenario (feet) 31 107 W 3RD 1272.49 1269.20 3.0 32 310 MAIN 1270.60 1268.54 3.7 33 103 E 3RD 1272.50 1269.38 2.8 34 315 MAIN 1269.96 1268.62 3.6 35 302 W 4TH 1270.95 1270.28 1.9 36 234 W 4TH 1272.21 1269.33 2.9 37 230 W 4TH 1270.62 1269.15 3.0 38 210 W 4TH 1273.30 1269.06 3.1 39 204 W 4TH 1271.59 1269.68 2.5 40 120 W 4TH 1271.16 1269.67 2.5 41 108 W 4TH 1269.54 1268.90 3.3 42 104 W 4TH 1272.25 1269.34 2.9 43 321 MAIN 1270.41 1268.45 3.7 44 324 MAIN 1269.58 1268.25 3.9 45 100 E 4TH 1270.54 1268.23 4.0
City Hall 1270.04 1268.52 46 100 E 4TH 1270.41 1268.49 3.7 47 403 MAIN 1269.72 1268.37 3.8
48 402 MAIN 0.00 0.00 49 405 MAIN 1270.04 1268.52 3.7 50 235 W 4TH 1271.31 1269.19 3.0 51 225 W 4TH 1272.29 1269.28 2.9 52 209 W 4TH 1271.38 1269.48 2.7 53 407 MAIN 1270.16 1268.51 3.7 54 203 W 4TH 1271.46 1268.79 3.4 55 121 W 4TH 1272.69 1269.21 3.0 56 117 E 4TH 1269.66 1267.70 4.5 57 119 W 4TH 1271.55 1269.31 2.9
58 115 W 4TH 0.00 1268.60
59 115 W 4TH 60 409 MAIN 1270.46 1268.58 3.6
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ID# Address First Floor Ground Flood Depth on Adjacent Ground Elevation Elevation for Primary Scenario (feet) 61 105 W 4TH 1272.18 1269.07 3.1 62 101 W 4TH 1272.25 1269.07 3.1 63 410 MAIN 1269.66 1268.42 3.8 64 411 MAIN 1270.01 1268.76 3.4 65 412 MAIN 1269.59 1268.41 3.8
66 unused point 67 413 MAIN 1270.16 1268.66 3.5 68 411 BARKER 1269.64 1267.69 4.5 69 205 E 4TH 1270.95 1267.83 4.4 70 217 E 4TH 1268.04 1267.24 5.0 71 415 MAIN 1270.28 1268.65 3.5
72 unused point 73 416 MAIN 1269.34 1268.36 3.8 74 417 MAIN 1269.95 1268.57 3.6 75 234 W 5TH 1272.03 1269.95 2.2 76 419 MAIN 1269.47 1268.46 3.7 77 202 W 5TH 1272.06 1269.33 2.9 78 124 W 5TH 1271.78 1269.03 3.2 79 122 W 5TH 1271.82 1268.83 3.4 80 104 W 5TH 1270.27 1267.45 4.7 81 423 MAIN 1269.94 1268.42 3.8 82 424 MAIN 1269.09 1268.30 3.9 83 114 E 5TH 1270.99 1268.48 3.7 84 124 E 5TH 1269.58 1267.87 4.3 85 410 BARKER 1271.72 1267.90 4.3 86 224 E 5TH 1268.51 1266.22 6.0 87 503 MAIN 1270.40 1268.44 3.8 88 502 MAIN 1269.75 1269.12 3.1 89 229 W 5TH 1274.94 1269.39 2.8 90 225 W 5TH 1272.56 1269.56 2.6
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ID# Address First Floor Ground Flood Depth on Adjacent Ground Elevation Elevation for Primary Scenario (feet) 91 221 W 5TH 1272.32 1269.83 2.4 92 217 W 5TH 1272.75 1269.64 2.6 93 215 W 5TH 1272.41 1269.54 2.7 94A 507 MAIN 1271.01 1268.56 3.6 94-C 507 MAIN 1269.45 1268.47 3.7 95 400 BARKER ST 1268.23 1267.30 4.9 96 201 W 5TH 1274.20 1269.59 2.6 97 125 W 5TH 1272.30 1269.44 2.8 98 105 W 5TH 1272.48 1269.21 3.0
99 105 W 5TH 0.00 0.00 100 103 E 5TH 1269.21 1268.62 3.6 101 510 MAIN 1273.72 1268.50 3.7 102 119 E 5TH 1270.93 1267.88 4.3 103 509 BARKER 1270.84 1267.26 4.9 104 502 BARKER 1276.24 1267.70 4.5 105 211 E 5TH 1271.49 1266.87 5.3 106 221 E 5TH 1269.86 1265.34 6.9 107 514 MAIN 1269.50 1268.65 3.5 108 236 W 6TH 1270.17 1269.93 2.3 109 228 W 6TH 1270.81 1269.62 2.6
City EMTs, Ambulance 110 515 MAIN 1270.06 1268.60 3.6 111 216 W 6TH 1271.48 1269.26 2.9
112 216 W 6TH 0.00 0.00 113 214 W 6TH 1271.98 1269.24 2.9 114 210 W 6TH 1273.02 1269.60 2.6 115 513 MARION 1273.00 1269.29 2.9 116 124 W 6TH 1271.47 1269.05 3.1 117 114 W 6TH 1272.21 1269.44 2.8 118 106 W 6TH 1270.94 1269.88 2.3
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Address First Floor Ground Flood Depth on Adjacent Ground ID# Elevation Elevation for Primary Scenario (feet) 119 521 MAIN 1269.65 1268.59 3.6 120 528 BARKER 1269.49 1268.09 4.1 121 217 E 6th ST 1267.47 1267.25 4.9 122 236 E 6TH 1269.49 1267.28 4.9 123 603 MAIN 1272.66 1269.18 3.0 124 233 W 6TH 1272.88 1270.85 1.3 125 227 W 6TH 1271.79 1269.63 2.6 126 225 W 6TH 1272.19 1269.47 2.7 127 221 W 6TH 1271.95 1269.41 2.8 128 213 W 6TH 1270.18 1269.34 2.8 129 601 MARION 1271.16 1269.44 2.8 130 605 MARION 1271.04 1269.26 2.9 131 604 MAIN 1271.23 1268.96 3.2
Unity Park 1270.79 1268.30 132 600 W 6TH 0.00 1269.64 2.5
Old school 1271.43 1268.89 133 111 W 6TH 1272.01 1269.26 2.9 134 609 MAIN 1271.83 1269.21 3.0 135 103 E 6TH 1271.14 1268.14 4.1 136 123 E 6TH 1268.25 1267.70 4.5 137 201 E 6TH 1271.63 1267.84 4.4 138 217 E 6TH 1270.79 1268.30 3.9 139 610 MAIN 1271.43 1268.89 3.3 140 613 MAIN 1271.03 1268.99 3.2 141 225 E 6TH 1268.43 1267.86 4.3 142 236 W 7TH 1276.00 1273.43 -1.2 143 228 W 7TH 1274.87 1272.03 0.2 144 222 W 7TH 1274.43 1271.39 0.8
145 unused point 146 208 W 7TH 1271.86 1270.33 1.9
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ID# Address First Floor Ground Flood Depth on Adjacent Ground Elevation Elevation for Primary Scenario (feet) 147 624 MARION 1271.88 1269.25 2.9 148 130 W 7TH 1272.56 1269.39 2.8 149 128 W 7TH 1271.36 1269.16 3.0 150 108 W 7TH 1272.55 1269.17 3.0 151 104 W 7TH 1271.89 1269.00 3.2 152 623 MAIN 1272.35 1269.16 3.0 153 624 MAIN 1272.27 1268.96 3.2 154 114 E 7TH 1270.84 1268.32 3.9 155 620 BARKER 1270.36 1267.39 4.8
156 unused point 157 236 E 7TH 1267.28 1267.28 4.9 158 703 MAIN 1271.21 1269.39 2.8 159 235 W 7TH 1273.99 1272.61 -0.4
160 229 W 7TH 0.00 1271.39 161 225 W 7TH 1273.04 1271.27 0.9 162 223 W 7TH 1274.27 1271.01 1.2 163 133 W 7TH 1271.50 1269.10 3.1
164 106 E 7TH 0.00 0.00 165 131 W 7TH 1273.74 1269.47 2.7 166 127 W 7TH 1273.60 1269.41 2.8 167 123 W 7TH 1271.56 1269.53 2.7 168 105 W 7TH 1270.50 1269.55 2.6 169 103 W 7TH 1272.42 1268.94 3.3 170 711 MAIN 1272.21 1269.28 2.9 171 117 E 7TH 1270.54 1268.14 4.1 172 235 E 7TH 1270.02 1268.00 4.2 173 714 MAIN 1270.79 1268.89 3.3 174 715 MAIN 1272.10 1269.58 2.6 175 236 W 8TH 1276.54 1275.70 -3.5 176 226 W 8TH 1272.21 1270.76 1.4
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ID# Address First Floor Ground Flood Depth on Adjacent Ground Elevation Elevation for Primary Scenario (feet) 177 218 W 8TH 1272.31 1269.96 2.2 178 210 W 8TH 1272.60 1269.51 2.7 179 202 W 8TH 1271.45 1269.24 2.9 180 726 MARION 1266.82 1269.42 2.8 181 112 W 8TH 1270.69 1269.14 3.0 182 108 W 8TH 1273.28 1269.19 3.0 183 721 MAIN 1271.63 1269.00 3.2 184 106 E 8TH 1270.26 1268.15 4.0
1271.94 1268.87 -1268.9 185 721 BARKER 1269.92 1268.15 4.0
186 805 MAIN 0.00 0.00 187 107 W 8TH 1271.02 1268.86 3.3
188 145 W 8TH 0.00 0.00 189 809 MAIN 1272.31 1269.39 2.8 190 810 MAIN 1272.43 1269.05 3.1 191 815 MAIN 1272.88 1269.69 2.5
192 810 BARKER 0.00 0.00 193 818 MAIN 1271.94 1268.87 3.3 194 231 W 8TH 1274.23 1271.61 0.6 195 834 MARION 1272.56 1269.81 2.4 196 110 W 9TH 1272.35 1269.46 2.7 197 203 W 8TH 1270.66 1270.07 2.1 198 817 MAIN 1272.79 1269.59 2.6 199 201 W 8TH 1273.85 1271.38 0.8 200 822 MAIN 1271.38 1268.70 3.5
Public Housing (HUD) 201 102 E 9TH 1269.81 1269.34 2.9 201-1 102 E 9TH 1269.79 1269.34 2.9 201-2 102 E 9TH 1269.55 1269.34 2.9 201-3 102 E 9TH 1269.63 1269.34 2.9
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ID# Address First Floor Ground Flood Depth on Adjacent Ground Elevation Elevation for Primary Scenario (feet) 201-4 102 E 9TH 1269.81 1269.34 2.9 201-5 102 E 9TH 1269.75 1269.34 2.9 201-6 102 E 9TH 1269.91 1269.58 2.6 201-7 102 E 9TH 1269.96 1269.58 2.6 201-8 102 E 9TH 1269.95 1269.58 2.6 202 905 MARION 1272.15 1270.13 2.1 203 911 MARION 1273.64 1270.36 1.8 204 901 MAIN 1273.11 1269.68 2.5
205 unused point 206 913 MARION 1273.61 1270.31 1.9 207 103 E 9TH 1271.41 1268.87 3.3 208 210 W 10TH 1275.82 1273.34 -1.1 209 206 W 10TH 1274.06 1272.14 0.0 210 915 MARION 1273.12 1270.65 1.5 211 914 MAIN 1271.30 1269.26 2.9 212 103 E 9TH 1269.31 1268.73 3.5
213 unused point
Public Housing (HUD) 214 109 E 9TH 1269.62 1269.52 2.7 214-1 109 E 9TH 1269.60 1269.52 2.7 214-2 109 E 9TH 1268.69 1269.52 2.7 214-3 109 E 9TH 1269.49 1268.54 3.6 215 1007 MARION 1275.51 1271.82 0.4 216 1003 MARION 1274.94 1271.23 1.0 217 209 W 10TH 1278.23 1274.96 -2.8 218 209 W 10TH 1274.29 1273.36 -1.2 219 1011 MARION 1275.58 1271.86 0.3 220 1012 MARION 1270.91 1270.46 1.7 221 109 W 9TH 1271.41 1270.25 1.9 222 1015 MARION 1277.48 1273.25 -1.1
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ID# Address First Floor Ground Flood Depth on Adjacent Ground Elevation Elevation for Primary Scenario (feet) 223 206 W 11TH 1281.06 1278.10 -5.9 224 1023 MARION 1277.27 1272.66 -0.5 225 1101 MAIN 1270.80 1269.03 3.2 226 1027 MARION 1270.80 1269.03 3.2 227 1300 MARION 1274.74 1272.71 -0.5 228 326 W 4TH 1272.82 1271.84 0.4 229 213 W 4TH 1271.56 1269.21 3.0 230 PUBLIC ROAD 1273.22 1270.95 1.2 231 233 W 10th 1280.95 1277.40 -5.2
232 511 main Same as Point 0.00 110 233 Doyle street 1274.60 1271.30 0.9 234 220 W 10TH ST 1277.62 1276.53 -4.3 235 234 W 10th 1279.05 1276.98 -4.8 236 238 w 10th 1281.34 1279.94 -7.8 237 238 w 10th 1284.20 1280.45 -8.3
238-299 unused points 300 232 w 4th 1272.31 1269.61 2.6 street 301 230 w 4th 1270.40 1269.40 2.8 street 302 303 w 4th 1270.86 1269.55 2.6 street 303 313 w 4th 1272.83 1269.69 2.5 street 304 Mid Kansas 1274.36 1273.32 -1.8 Cooperative 305 Mid Kansas 1274.42 1272.41 -0.9 Cooperative 306 Mid Kansas 1275.82 1271.44 0.0 Cooperative 307 Mid Kansas 1270.88 1270.33 1.2 Cooperative 308 501 DOYLE 1271.46 1270.86 1.3 309 415 DOYLE 1272.67 1270.42 1.8
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ID# Address First Floor Ground Flood Depth on Adjacent Ground Elevation Elevation for Primary Scenario (feet) 310 413 DOYLE 1273.31 1270.17 2.0 311 521 DOYLE 1272.10 1271.00 1.2 312 601 DOYLE 1272.93 1270.81 1.4 313 621 DOYLE 1277.65 1273.68 -1.5 314 726 MARION 1270.17 1269.93 2.3 315 302 W 8TH 1286.61 1283.58 -11.4 316 300 W 8TH 1283.50 1279.22 -7.0 317 298 W 8TH 1277.84 1273.75 -1.6 318 210 W 8TH 1271.70 1269.88 2.3
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4.0. Flood Risk Management Menu of Measures A full menu of measures is available to manage flood risks. Considering each community, as well as individual properties, a smaller subset of the full menu of measures is more appropriate based on their unique situations. The existing conditions of physical, geographic and other characteristics means many measures are not options. The process of deciding on the best measures is an exercise only a local community can do, and the result is the story, the playbook on floodplain management, and sometimes called a flood risk management plan. The tools in that toolbox depend greatly on the unique local situation. Geography, amount of river flow, and a number of other variables can physically affect how each measure may work. Some measures are not feasible due to cost. Community cohesion is also an influencing factor. And frequently the stakeholders simply based on their own preferences do not want certain measures used. As a result, knowing the smaller subset of those most appropriate measures is helpful, and the project team refers to these as risk management options. From these, the community, public or private, property owners will select their flood risk mitigation actions. The federal, state, and local partners also refer to other subsets of the full menu of flood risk management measures. The subsets of measures are sometimes arranged, or referred to, as follows: • structural or nonstructural (nonstructural flood risk adaptive measures), • physical or nonphysical, and • features or (floodplain management) activities. This manner of binning measures, labeling as subsets, or subcategorizing, may help the public understand these measures. For some, these subsets are confusing when explained and used inconsistently. To further help the communities and property owners understand the measures, Appendix A offers a complete flood risk management glossary. The sections below provide more information specifically on the risk management options that are available at the property owner level. Structural measures are features and are commonly recognized solutions. These include dams, channels, and levees, such as those near Florence including the Marion Reservoir and the Florence Levee. The USACE is well known for providing the more heavy lift in funding the construction of large features. However, the misconception is that these are the only measures that can help. Without the incorporation of these supplementary mitigation measures, the buildings identified in this study, and within a leveed area, will still have a low risk of being damaged from flooding occurring in the future. While measures, like flood proofing, elevating buildings, doing buyouts, and relocating buildings, are specific to the individual building being investigated, when considered for the mitigation of flood damages, the cumulative effect is to determine a broader, community level strategy. This strategy incorporates a full range of measures which are economically feasible, socially acceptable, environmentally adequate, and will reduce the cumulative risk of flooding. And, when combined with a levee, they improve flood resilience.
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Each individual building assessed may require a different nonstructural technique. While this assessment relies on data collected in the field and provided by the county for implementation, the assessment is not conclusive as to the ultimate feasibility of the measure. Because of the limited nature of this investigation, this assessment was conducted as planning level detail and would require additional analyses to determine economic feasibility for implementation. Flood proofing, elevating buildings, doing buyouts, relocating buildings, and other measures like adding flood openings in foundations, require different …additional risk implementation methods than structural measures. Since each building is owned management options will and typically occupied, nonstructural implementation agreements must be entered be less cost effective when into with each individual owner, and this is typical for USACE in cooperation with combined with a levee, a community under USACE programs. These measures for mitigating floods for however, the measures individual buildings are proven methods and are techniques specifically directed at add resilience and enable reducing flood risk and flood damages in floodplains. The project team recognizes communities to endure these additional risk management options will be less cost effective when flooding and thrive. combined with a levee, however, the measures add resilience and enable communities to endure flooding and thrive. Many buildings across the nation benefit from reduced risk and damage or no risk and no damage due to implementation of nonstructural measures. Nonstructural measures are very effective for both short and long term flood risk and flood damage reduction and can be very cost effective when compared to building features (ie. levee systems, dams, and channels) measures. The ability of nonstructural measures to be implemented in very small increments, each increment producing flood risk reduction benefits is an important characteristic of this form of flood risk management. Also important is the ability to implement measures over intermediate and long periods such that layering of measures, each one providing a higher degree of risk reduction, is possible and given both federal and nonfederal funding constraints, may be probable.
4.1. Nonstructural Flood Risk Adaptive Measures
The overall purpose of a nonstructural flood risk adaptive measure is to reduce flood risk, decrease flood damages, and to potentially eliminate life-loss. Flood risk adaptive measures are the tools used at the property owner level to reduce flood risk. Flood risk adaptive measures are the modifications to the characteristics of vulnerable buildings and buildings that are subject to flooding or are modifications about the behavior of people living in or near floodplains. In general, nonstructural measures do not modify the characteristics of floods (stage, velocity, duration) nor do they induce development in a floodplain that is inconsistent with reducing flood risk. Some nonstructural measures that can be formulated for implementation include removing buildings from the floodplain by relocation or acquisition; wet or dry flood proofing buildings; implementing flood warning and emergency preparedness activities; and implementing floodplain regulation. The National Flood Insurance Program is also considered among nonstructural measures since the program’s specific activities include minimum standards for floodplain regulation, flood insurance, and flood hazard mitigation. Some flood risk adaptive measures considered for flood damage reduction by USACE, such as dry flood proofing a residential building, does not result in a flood insurance premium reduction for the owner of a residential property. The intent by USACE is to design an engineered application of dry flood proofing which will reduce future flood damages to that building. In contrast, structural measures, including features like dams, levees, and channels, reduce flood risk by modifying the probability or frequency of flooding at a particular location. Structural measures do not modify the characteristics of existing development in the floodplain. While structural measures may decrease the frequency of flooding at a specific location, they can actually increase flood risk if the consequences of flooding are allowed to increase through development.
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Some of the basic considerations used to develop nonstructural measures are as follows: • Relocate buildings from the floodplain to a flood-free location. • Acquire the floodplain land on which the relocated buildings previously existed and enforce deed restrictions so the land will never be developed in the future for uses that are subject to flood risk. • Acquire floodplain land that is in existing open space use to prevent future development that could be at flood risk. • Acquire buildings within the floodplain, demolish them, and enforce deed restrictions to prevent future development that could be at flood risk. • Elevate buildings to above a specified flood elevation. • Dry flood proof buildings (traditional structure waterproofing) • Wet flood proof buildings (retrofitting existing structures below a design flood elevation with water resistant materials and allowing floodwater to flow through the structure). • Develop evacuation procedures. • Develop public alert flood warning systems. • Develop and implement emergency action plans. • Employ educational outreach programs aimed at reducing flood risk. Each of these general categories of nonstructural measures can be applied as a single measure or can be applied in combination with one another or with structural measures to reduce or eliminate flood risk. The range of benefits, costs, and residual damages associated with application of each measure is broad. The extent and severity of social and economic impacts associated with the various measures can be likewise broad and must be identified for any plan. Depending upon the nonstructural measures selected for application and the relative percentage of each applied, the future land use pattern of the area could look considerably different in specific areas. The consequences associated with locating damageable property and people within floodplain areas can be extreme to property owners and floodplain occupants. Within the context of this assessment, an objective is to identify strategies and measures that can be used in tandem to reduce flood risk. Some strategies and measures may be more appropriate for Federal action while others will be more attuned to local regulatory action and administration. In either case, these measures must be effective, socially acceptable, environmentally suitable, and mindful of the existing neighborhood and community social and economic systems within which they would be implemented. This report, based on expertise from the USACE National Nonstructural Committee recommends and the USACE Kansas City District identifies such nonstructural measures.
4.2. Protecting Critical Facilities
Structures or infrastructure, which provide services for health, welfare, and public safety, and which may become inoperable during a flood event resulting in additional adverse impacts or hardship on the affected population, are considered critical facilities. Essentially, whatever the community identifies as critical, should be addressed, so a community could even, for example, explain that a particular road is considered critical infrastructure, or maybe a bridge, as well. These critical facilities are essential during a flood to provide health, welfare, and human safety to the public. Critical facilities are generally those services required during the flood such as • police and fire protection, • emergency operations,
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• evacuation sites, and • medical services. Facilities which house the elderly, disabled, or requiring medical assistance, require extensive evacuation time are considered significant. Facilities that could, if flooded, add to the severity of the disaster such as power stations, wastewater treatment plants, and toxic material storage sites are considered critical. Each significant and critical facility within the guidelines of Executive Order 11988 should be located at a flood free site, if federal funding is involved. If this is not possible or practicable, the facility should be located external to the 0.2% annual chance exceedance flood event floodplain. If this is not possible or practicable, the facility must be, at a minimum, protected to the extent that it can function as intended during all floods up to and equal to an event of that 0.2% ACE. While this is a federal guideline, this is also the project team’s recommendation to help communities like Florence be resilient to flooding. The project team created a list of critical facilities in Table 7-3, List of Land Survey Point Numbers for Critical Facilities and Public Property. However, the community leaders may wish to refine that list.
4.3. Common Nonstructural Flood Risk Adaptive Measures
The following flood risk adaptive measures are commonly utilized for reducing flood risk within urban and rural areas across the nation. Each measure must meet specific criteria that would make it acceptable to addressing the flood characteristics and site conditions. Some measures, due to the characteristics of the flood event, site location, and building characteristics, are more implementable than others. This assessment strives to identify the most effective measure for implementation. Specific figures are included to help the property owners understand each measure, and the figures will have some abbreviations. The base flood elevation is BFE. The lowest adjacent grade is LAG. These terms are important to understand as they are specific terms used in the National Flood Insurance Program. 4.3.1. National Flood Insurance Program The National Flood Insurance Program (NFIP) contains 3 basic parts: • flood insurance, • flood mitigation, and • floodplain regulation. In terms of reducing flood risk, only flood mitigation and floodplain regulation have a direct impact in theory. In regards to the flood insurance part of the NFIP, flood insurance simply spreads the flood risk across multiple properties as does any insurance program. So, a policy does not reduce flood risk. Rather, having a policy in force helps a property owner share or distribute the flood risk. In terms of the NFIP as a nonstructural measure to truly reduce flood risk, the flood mitigation and floodplain regulation parts of the NFIP are those measures. Five mitigation programs exist within the NFIP. They are the hazard mitigation grant program, pre disaster mitigation grant program, flood mitigation assistance program, repetitive loss program, and severe repetitive loss program. Within the floodplain regulation part of the NFIP, this serves as a nonstructural measure indirectly through adoption of minimum floodplain management standards by communities participating in the NFIP.
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4.3.2. Floodplain Regulation and Floodplain Management Floodplain regulation and floodplain management have proven to be very effective in reducing flood risk and flood damage. The basic principles of these tools are founded in the National Flood Insurance Program (NFIP) which requires minimum standards of floodplain management and floodplain regulation for those communities that participate in the NFIP. While the minimum standards have not resulted in substantial flood risk reduction, incorporation of more stringent building codes and zoning ordinances may meet community objectives of eliminating flood risk. Communities can establish more stringent ordinances. 4.3.3. Public Alert and Flood Warning Public alert and flood warning are both measures classified as nonphysical nonstructural techniques and are applicable to the entire study area. Communities should consider the development and implementation of flood warning systems and also tie the warning system to their emergency action plan (see next section). The development of such plans and the installation of pertinent equipment such as data collection devices (rain gages, stream gages) and data processing equipment can become an integral feature of a project. 4.3.4. Emergency Action Planning Another measure classified as an activity and a nonphysical nonstructural techniques and applicable to the entire community is emergency action plans (EAPs). Any flood risk management plan should consider the development and implementation of an EAP along with a flood warning system. The development of EAPs may also, although not required, include the installation of data collection devices (rain gages, stream gages) and data processing equipment and might be made an integral feature of a project. Communities should consider developing the EAP and then exercising that plan on a recurring basis. The USACE and FEMA strongly suggest doing an annual tabletop exercise with the county and neighboring communities. These events allow community staff to make a friend before they need a friend in the “12th hour,” that is, at the time of the flood disaster. Staff can receive valuable training, pass on knowledge, and discover weakness in plans and assumptions. 4.3.5. Evacuation Planning Evacuation planning should consider vertical evacuation as well as lateral evacuation. In urban areas, vertical evacuation routes are offered in tall buildings. Suburban and rural areas face more challenges, including the additional constraints of surrounding terrain and, for leveed areas, the confluence of more than one river or creek. Reunification sites should be a featured component of any evacuation plan. Evacuation planning is also classified as a nonphysical nonstructural techniques that is applicable to the entire study area. Any community playbook for managing flood risks should carefully consider the logistics involved with evacuation. Evacuation planning should consider vertical evacuation as well as lateral evacuation. In urban areas, vertical evacuation routes are offered in tall buildings. Reunification sites should be a featured component of any evacuation plan.
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4.3.6. Flood Openings in Foundations Perimeter wall foundations can enclose flood prone spaces, however, for new construction and or substantial improvements, the NFIP has requirements for flood openings. These may also be referred to as permanent openings or engineered openings. While a crawlspace is a good way to elevate a building a couple of feet, the floodwater should be allowed to enter and equalize the water pressure on both sides of the foundation wall to prevent collapse.
These should not be confused with air vents for crawl Figure 4-2. A collapsed foundation from the spaces, because flood openings require the ability to Labor Day Flood in Manhattan, KS in 2018. allow water as well as air to pass through. The openings should be no higher than 12 inches above the adjacent ground. At least two openings are part of the NFIP requirement on different sides of the building, as well. More important is that the area of these flood openings must provide one square inch of net open area for every square foot of area enclosed by the perimeter walls. Flood openings may have screens to allow only water in, but the total area requirement must still be met. Prefabricated flood vents or flood louvers are available by qualified manufacturers that are familiar with the NFIP requirements. FEMA’s document, Openings in Foundation Walls and Walls of Enclosures (August 2008) will help property owners properly address flood openings.
Figure 4-1. Crawl space detail showing flood opening.
Figure 4-3. Examples of typical air vents used as flood openings, where net open area varies.
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4.3.7. Utility Service, Equipment, and Tanks A variety of utilities have a buoyant force that can result in the utility floating away during a flood and posing a serious danger to the public, so a floodplain mangers recommend anchoring and elevating these items. These include heat pumps, air conditioners, sanitary service tanks, and especially fuel or propane tanks. Agricultural tanks for fertilizer should also be secured and elevated. The fuel tanks can release contents during severe floods, and these should be underground, elevated on platforms or columns, or at- grade with anchors to reside loads. At-grade tanks should also consider protective fencing to reduce puncture by floating debris. 4.3.8. Manufactured Homes Manufactured homes and trailer homes should be elevated above floodwaters. These must be anchored to reinforced foundations to resist flotation, collapse, and lateral movement and should be tied down in accordance with community ordinances or manufacturers’ installation specifications for the special flood hazard areas according to the NFIP.
Figure 4-4. Building section of proposed mitigation: showing an elevated manufactured home, an elevated utility, and proper anchoring for the home as well as the tank.
4.3.9. Buyout with Demolition/Salvage of the Building This measure consists of purchasing the building and the associated land from the owner as part of the measure. The building is either demolished or the building is sold to others and relocated to a location external to the floodplain. In some instances, communities are finding a benefit in salvaging materials (wiring, plumbing, fixtures) from acquired buildings rather than filling up landfills with the demolished building. Development sites, if needed, can be a consideration as part of project development in order to have locations where displaced people can construct new homes or businesses.
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4.3.10. Relocation of Building This measure requires physically moving the at-risk building and purchasing the land upon which the building is located. This measure achieves a high level of flood risk reduction when buildings can be relocated from a high flood hazard area to an area that is located completely outside of the floodplain. Development of relocation sites where buildings could be moved to achieve the planning objectives of reducing flood risk and retaining such aspects as community tax base, neighborhood cohesion, or cultural and historic significance can be part of any relocation project. This measure could be applicable within the study area. 4.3.11. Removal of Basement This measure consists of relocation of basement storage, utilities, mechanical equipment, electrical panels and circuits to above the base flood elevation (BFE) or design flood elevation (DFE). The existing basement is then filled without elevating the remainder of the building if the buildings’ first floor is currently located above the BFE or DFE or whichever is higher. Placing an addition onto the building as part of the measure could occur to compensate for the loss of habitable basement space to the owner and to house the furnace, water heater, water softener and other utilities and appliances. If the addition could not be developed because of limited space within the property parcel or because the owner did not want it, partial compensation for the lost basement space would be negotiable. Typically, basement space is not of the same value as above ground finished space. 4.3.12. Elevation of Building This measure requires lifting the entire building or the habitable area above a specific flood elevation, as shown in Figure 4-5. If a basement exists and had been fully developed prior to elevation and could not be developed post- elevation, compensation for removal of the basement space would be in order to the owner. Typically, basement space is not of the same value as above ground finished space. This measure is applicable anywhere within the study area unless the required elevation is greater than a maximum of 12 feet above the adjacent grade, where the recommendation would be for acquisition or relocation. Velocity and hydrodynamic forces on the structure would also have to be considered to ensure stability of the elevated building.
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Figure 4-5. Elevation of Structure (Diagrammatic Section).
4.3.13. Dry Flood Proofing This measure consists of waterproofing the building or covering the exterior wall with a permanent impermeable membrane and sealed doors and windows. While this measure is generally acceptable with commercial buildings, property owners may conduct dry flood proofing on residential homes as well as all other types of buildings. Nonresidential buildings can receive a flood insurance premium reduction, provided they are flood proofed to at least one foot above the base flood elevation. Dry flood proofing on residential buildings is not recognized by the NFIP for any flood insurance premium rate reduction and is not recognized for compliance purposes either. An example is shown in Figure 4-6. Only nonresidential buildings are eligible for the premium reduction for dry flood proofing. This measure achieves flood risk reduction benefits, but has two draw backs in flood insurance regulations: Based upon testing, a “conventional” built building can generally be dry flood proofed up to between three to four feet on the exterior walls. A structural analysis of the wall strength would be required if it was desired to achieve a higher level of protection. A sump pump and perhaps French drain system may be required as part of the project to remove seepage or interior drainage. Closure panels Only are required for all openings. This concept does not work with basements or crawl spaces due to the possible long duration of nonresidential flooding, unless complex and expensive cut-off walls are integrated buildings are into the design. These walls would resist failure of the basement/crawlspace walls and essentially failure of the entire eligible for the building envelope. For buildings with basements and/or crawlspaces, the only way that dry flood proofing could be considered to work is premium for the first floor to be made impermeable to the passage of reduction for dry floodwater. flood proofing. If a property owner is considering dry flood proofing to reduce the flood risk, the USACE National Nonstructural Committee
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recommends that the property owner use closure barriers which have been certified through the National Flood Barrier Testing and Certification program. The purpose of the testing program is to provide a process for evaluating flood fight products in terms of their resistance to floodwaters, their material properties, and consistency of product manufacturing. Products are tested against water forces in the USACE Engineer Research and Development Center laboratory, tested against material forces in an FM Approval laboratory setting, and undergo periodic inspection of the manufacturing process for consistency of product. Additional information regarding the certification program can be found at the following Association of State Floodplain Managers web site: http://nationalfloodbarrier.org/
Figure 4-6. Dry Flood Proofing (Diagrammatic Detail).
4.3.14. Wet Flood Proofing. This measure is applicable as either a stand-alone measure or as a measure combined with other nonstructural measures such as elevation or dry flood proofing. As a stand-alone measure, all construction materials and finishing materials to a specified height are required to be water resistant. An example is shown in Figure 4-7. All utilities must be elevated above the design flood elevation. Because of these requirements, wet flood proofing of finished residential buildings is generally not recommended. The NFIP does not recognize wet flood proofing for any insurance premium reductions on residential buildings. The NFIP does give credit property owners’ premiums for buildings that are wet flood proofed with no basements, that are elevated, and that have the proper flood openings. This is available for both residential and nonresidential properties. Wet flood proofing is applicable to commercial and industrial buildings and should be considered for combining with a flood warning system, flood preparedness, and flood response plan. This measure is generally not applicable to large flood depths and high velocity flows due to possible failure of building walls.
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Wet flood proofing can also include the idea of elevating a floor within buildings with very tall first floor clearances. These are more common nonresidential buildings. Some more modern residential buildings may have this as an option, too.
Figure 4-7. Wet Flood Proofing (Diagrammatic Detail/Section)
4.3.15. Berms, Levees, and Floodwalls Although these items are structural in nature, and if considered for implementation by USACE, require standard USACE structural design criteria, they can sometimes be applied to individual buildings without adversely impacting the floodplain by increasing stages, velocities, or durations. These measures are intended to reduce the frequency of flooding but not eliminate floodplain management and flood insurance requirements. An example is shown in Figure 4-8.
Figure 4-8. Berms, Levees, Floodwalls (Diagrammatic Detail).
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4.3.16. Land Use Regulation Land use regulation is city or county codes or ordinances that guide development and manage flood risks. The regulations are equitably applied local policies, sometimes at the city or county level, but also at the state level. Regulations at the local level include ordinances, building codes, zoning, and stormwater setback ordinances, freeboard ordinances, sanitary codes, and housing or subdivision regulations are also examples. Funding laws may also be considered a form of regulation and serve to support flood risk management, including mill levies that might fund a drainage district’s functionality, stormwater utilities that serve to support capital improvement projects, and even sales taxes on particular development. Local design manuals are tied to policies and may be considered an extension of flood risk management regulations, such as stormwater detention basin volumes and release rates used by local planners in the process of reviewing development plans. Communities also may have comprehensive plans or watershed planning documents that tie to regulations. A floodplain ordinance is the most common regulation, which is required for flood insurance. Land use regulation is considered a nonphysical nonstructural measure. Land acquisition can be in the form of fee title or permanent easement with fee title. Land use after acquisition is open space use via deed restriction that prohibits any type of development that can sustain flood damages or restrict flood flows. Land acquired as part of a nonstructural project can be converted to a new use such as ecosystem restoration and/or recreation that is open space based such as trails, shoreline access, and interpretive markers and possible ball fields. Conversion of previously developed land to open space means that infrastructure no longer has need for utilities, streets, and sidewalks which can be removed as part of the project. By incorporating “ new uses of the permanently evacuated floodplains” into the nonstructural flood risk reduction project, economic feasibility of the buyout or relocation projects is enhanced due to transfer of some flood risk management costs to ecosystem restoration and by adding the benefits and costs of recreation.
4.3.17. Beneficial Use Beneficial Use of floodplains is a useful way to go beyond managing flood risks, encourage a more diverse natural environment, and add recreational amenities in what is regarded as a wise use of floodplains. Communities also find this adds value in terms of social benefits, which help the community thrive.
4.4. Temporary Flood Risk Adaptive Measures
This section of the report focuses on the use of temporary measures and the precautions which should be considered prior to implementation. Temporary flood proofing measures are those which, in order to protect a building and contents within, must be implemented every time the property has a risk of flooding. The responsibility for flood proofing, including the detailed planning, purchase of flood proofing materials, and implementation, lies solely with the property owner or tenant of each building. Each owner or tenant should weigh the costs associated with implementing temporary flood proofing measures numerous times as opposed
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to the long-term security and peace of mind that can come with implementing permanent measures. Reducing flood risk is an objective which should be conducted through permanent measures. Knowing the characteristics of flooding, such as the available warning time for making to preparations, the projected depth of floodwaters, and the areal extent of flooding, along with the anticipated duration, are all factors which will allow community officials, business owners, and homeowners to make personal decisions regarding their ability to reduce property damages. While the most effective and efficient process for reducing property damages is to implement permanent measures, where even features such as doorway and window barriers can be readily installed, the property owners may need interim temporary measures until permanent measures can be implemented. The project team recommends that each owner transition to more permanent flood prevention measures as soon as reasonably possible. 4.4.1. Common Temporary Flood Risk Adaptive Measures Some of the most common temporary measures for the buildings are 1) polyethylene sheeting hung on the building exterior (usually to a height of 3 feet above the first floor elevation and continued on the ground surface 4 feet from the structure exterior), in combination with door and window closures, 2) clear liquid sealant applied to the building exterior, in combination with caulking of large cracks in the exterior and placement of door and window closures, 3) sandbag berms located around all or a portion of the building, and 4) any of the barriers certified through the National Flood Barrier Testing and Certification Program (see http://nationalfloodbarrier.org/). A key difference between these temporary measures is that hydrostatic forces are applied to the building walls when using the polyethylene sheeting and clear liquid sealant measures, but not with free standing sandbag berms or the certified barriers. 4.4.2. Implementing Temporary Measures Implementation of temporary measures can be successful in reducing or preventing flood damages when conducted correctly. The scope of this Silver Jackets study does not allow the USACE Kansas City District to evaluate the individual buildings and their sites in sufficient detail to guarantee the success of temporary flood proofing, as the owner or tenant must consider several factors when implementing temporary measures:
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• Because of the serious nature of flooding and because of unknowns associated with the depth, velocity, and duration of flooding, as well as the precise structural condition of each building, the project team recommends temporary flood proofing measures be placed to a height which does not exceed three feet above the elevation of the first floor of the building. The hydrostatic forces of the floodwaters can cause a catastrophic collapse to the walls of a building due to the lack of lateral resistance from the structure as the floodwaters rise higher against the sides of the building. And, since the characteristics of a flood (the depth, velocity and duration) may change during a flood event, a possibility for failure of foundations, walls, and closure panels to occur at a flood depth of less than three feet still remains. Without a proper structural analysis of individual buildings by a certified professional or contractor, failure of a structure can occur due to the hydrostatic and hydrodynamic pressures caused by water pooling up against or running into a building. The USACE National Nonstructural Committee highly recommends that after the flood proofing measures have been implemented, all persons evacuate the building to a predetermined location of safety. • As mentioned in the section, Flood Risk Assessment, flooding is a City staff can minimize continuum of possible events, so a building could be exposed to a wasting time and flood event of a depth greater than for which temporary flood money spent flood proofing measures have been erected. fighting when • Smaller, more frequent storm events that can cause localized flooding can occur in the community area. In these events, there understanding and may not be sufficient warning time for the owners or tenants to monitoring projected implement the temporary measures. stages in flood • For less frequent and more severe rainfall, property owners should forecasts familiarize themselves with NOAA National Weather Service flood warnings and U.S. Geological Service gages well in advance to allow time for activating temporary barriers. • City staff can minimize wasting time and money spent flood fighting when understanding and monitoring projected stages in flood forecasts. When available, NOAA National Weather Service flood warnings and U.S. Geological Service gage information can be used to mobilize flood fighting materials, such as sandbags, or preposition road closures signs that public safety officers can close roads as overtopping is imminent. • Preparing a building for a flood requires significant effort, and even engineers and forecasters find accurately predicting the floodwater depth even one day in advance impossible. Therefore, the owner or tenant cannot be certain that the projected flood event will actually occur. The owner or tenant must find his own comfort level and balance the risk of not having the building properly flood proofed, versus the risk that the effort to flood proof was not necessary. • In order to prevent unsanitary water from backing up into the building during a flood, the owner should ensure that his sanitary drain line is fitted with a back-flow preventer. This can be found from reliable venders on the internet in advance of flooding, and these typically require only a short amount of time to implement. • Downspouts and associated drainages must be considered. If a certified barrier or sandbag berm is erected, the downspouts need to be modified so they can be directed over the barrier; this would greatly reduce the amount of water to be pumped from within the protected area. Also, there may be drain lines that carry water from the downspout that pass under the certified barrier or sandbag berm, which must be plugged to prevent floodwater from flowing through the line into the protected area. • If the exterior construction is not structurally sufficient to withstand a significant water load the force of water at a depth of three feet (or perhaps less) could collapse walls. For placement of polyethylene
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sheeting on the exterior of a building, the property owner may consider having temporary measures include a thick layer of plywood (up to 1 inch) attached to the exterior surface of the building up to the level of protection. The plywood could be attached to wall studs using countersunk threaded anchors with bolts, and sheeting would be placed over the plywood. Again, structural evaluation by a certified professional or contractor is recommended. 4.4.3. Flood Characteristics Dictating Temporary Measures Numerous characteristics associated with temporary flood proofing may be unknown to the owner or tenant. Some of these include 1) characteristics of the flood itself (depth, duration, and velocity). (Note that velocities will generally be greater near the channel), 2) the precise condition of the building being protected (condition of the foundation, crawlspace, basement, and type of construction of the first floor and side walls), and 3) the surrounding site conditions (whether the soil is permeable or impermeable, and the density of landscaping, the location of utilities as well as other external features). 4.4.4. Planning and Preparation of Temporary Measures The information provided in this report section is the basis for developing temporary mitigation measures to reduce the possibility of extensive flood damages. In order for flood proofing to be successful, a thorough plan for each individual building needs to be developed and implemented. The plans will vary from building to building, depending upon structure type, projected depth of flooding, the velocity of floodwaters, the time available to implement the measures, and the availability of flood proofing materials. In some instances, due to the depth of flooding or the projected velocity of the floodwaters, rather than attempt to keep floodwater out of the building, it may be more cost effective to remove or elevate to a higher interior location, those items (business records, electronics, computers, heirlooms, artwork, etc.) which contain a high value, intrinsic or monetary, so as to avoid exceptional loss. For individuals wishing to implement temporary flood proofing measures, a plan should be developed to ensure that the measures can be employed as quickly as possible when the threat of flooding is imminent. Locations for storage of the materials and equipment should be designated far in advance of an event. Storage can occur on or off-site; however, if materials and equipment are maintained off-site, arrangements should be made to transport these materials and equipment to the site for implementation. Because the limited time available to install temporary measures is a critical factor in the prevention of flood damages, site preparation, maintaining the proper inventory of flood proofing materials, and having a well prepared emergency response plan are crucial to a successful outcome. Early preparation can make the difference between minimal dollar damages and a catastrophic loss. While even the best laid plans may go awry, nationwide data indicate that the owners who pay attention to the details, establish a thorough step-by-step process for implementing their temporary flood proof measures, and prepare themselves and their buildings prior to the start of the flood season, fare far better than those individuals who rush against time to install temporary measures which have not been thoroughly planned out. The building owner or tenant must prioritize acquiring and placing materials in advance and determine the type and amount of materials required to be on hand each year through the forecasted flood season. A checklist of these items or material requirements should be prepared, including the sequence of placement of materials in order to establish the most time-effective process for implementing the temporary measures. Each year prior to the start of the flood season, the owner or tenant should review the checklist, replace missing or damaged items, and prepare to implement the entire flood proofing measure during the first signs or indication of imminent flooding. In addition, the owner and/or tenant should develop a procedure for ensuring that all employees, residents and others who may have been in the building prior to the flood event are accounted for after evacuation. This may be accomplished by planning to contact all personnel via cell phone and/or by arranging to meet at a designated location.
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Once the owner or tenant has established a temporary protection plan for the building, testing the plan for efficiency and effectiveness in order to optimize the plan is beneficial. The flood fight materials and equipment should be stored in such a manner that they will not be damaged and should be monitored on a regular basis to ensure that these materials will be effective when and if needed. For instance, blue plastic can become damaged with holes from animals or normal weathering and should be replaced if any damage occurs, and plywood should be stored such that it will not rot or be damaged by termites or storage in a wet or damp environment. While protection of the building and of the building contents are of high importance, during any flood event there is a possibility of extensive damage to the structure. Worth repeating, in order to prevent extensive loss or damage to high value items, the USACE National Nonstructural Committee recommends that the emergency response plan also consider relocating away from the building or to a higher elevation, those items which would be difficult or impossible to replace. Again, property owners must understand that the intent of these proposed measures is to provide only temporary protection from flooding. After the temporary measures have been implemented, after the sump pump(s) has been positioned and flooding appears to be imminent, the owner and all associated persons should evacuate the premises during the flood event. Catastrophic failure of a building’s structure, becoming trapped at the property due to rapidly rising floodwaters, and or loss of life could occur during a flood event. 4.4.4.1. Site Preparation The type and amount of site preparation will vary with each building. For many buildings, one of the recommendations is that, in order to prevent floodwaters from entering a building and causing damage, the site surrounding the building be prepped to a condition which allows relatively easy and quick installation of temporary flood proofing measures. For each building, the owner or tenant should try to achieve at least 4 feet of leveled access area around all exposed sides of the building. The placement of polyethylene (also known as polyurethane or plastic) sheeting and/or sandbags as a preventive barrier to flooding requires a leveled surface in order to resist seepage into the protected area. While shrubs, flowers and trees provide character and add value to a property, property owners need to understand the importance that they be removed from within the “leveled access area” in order to establish a preventive barrier to flooding. If the owner is unable to remove landscape items, a uniform barrier of protection is important to establish by placing polyethylene sheeting or sandbags as close to the protruding plant as possible to develop a cohesive barrier between the ground and the employed flood proofing measures. Even a small weakness in the flood proofing measure could result in catastrophic failure and damage. In certain circumstances, the owner may benefit from identifying appurtenances such as fence posts, gates, storage sheds and utility boxes which may prevent the establishment of a waterproof barrier. These items should be removed as much as possible from the “leveled access area.” Utilities and HVAC units must be considered. Where possible, vital utilities and HVAC units should be raised in height to a reasonable level. Otherwise, provisions in the flood proofing plan need to include the protection of these utilities and units. Also, these items are usually associated with wall openings through which floodwaters may enter a building. These openings must be sealed, along with any other holes or cracks in the exterior walls and foundation. 4.4.4.2. Removal of Interior Flood Water The removal of floodwaters from a building to prevent inundation of the first floor can be one of the most important and critical ways to protect a building from flooding. The use of sump pumps is one of the best and easiest methods to accomplish this. For most of the assessed building, the Corps’ recommendation is to install one or more sump pumps. Loss of electricity during a flood event must also be considered; therefore, the USACE National Nonstructural Committee recommends that the owner provide pumps that
53 | Page USACE-Kansas City District, Silver Jackets Program September 2018 can be powered with a battery power supply. In most cases, the installation of these pumps is relatively simple, and in some cases, the use of multiple pumps may be necessary. 4.4.4.3. Materials and Equipment Required for Temporary Measures The owner should ensure that the materials recommended for protecting the building have been obtained prior to the start of the flood season. Materials required for implementing a preventive barrier to flooding should be stockpiled in an accessible location. Materials remaining from the previous flood season should be inspected to determine condition for reuse. Some of the more frequent materials required for implementing successful temporary flood proofing measures includes: • Polyethylene Sheeting. This sheeting material (also known as visqueen, polyurethane or plastic sheeting) is often recommended for use when employing a temporary waterproof barrier around a building. The sheeting should be purchased in rolls, typically 5-6 mils thick, and will be cut long enough to extend from no more than 3 feet above the first floor of the building to, at a minimum, 4 feet out from the structure. The further the “leveled access area” and polyethylene material extend beyond the exterior wall of the building, the longer the flow path for floodwaters to enter a building, including the crawlspace or basement, is extended, increasing the resistance to flooding. The shorter the flow path is to a foundation, the higher the risks of complete soil saturation around a foundation, resulting in complete inundation of the crawlspace or basement. Once the floodwaters have access to the crawlspace or basement, it becomes more difficult to remove the floodwaters and to prevent or limit damages. • Connectors for Attaching Polyethylene Sheeting to Building Exterior. The type of connector needed depends upon the type of exterior surface of the building to which the sheeting is being fastened. Hooks, whether self-tapping or through drilled anchor connection, are normally recommended for use in fastening the polyethylene sheeting to the building. Spacing of the hooks should be such that no span is greater than 2 feet. Hooks should be placed permanently for continuous use from one flood season to the next. • Water Resistant Tape for Polyethylene Sheeting. For firm cohesiveness between the polyethylene sheeting and the exterior building surface or between adjacent polyethylene sheets, this type tape is recommended for use. These tapes incorporate PVC adhesives and are ideal for use in outdoor situations. Consideration should be made for vinyl coated cloth tapes for effectiveness where product performance is critical; these tapes can sustain harsh weather conditions and can be used for repairs to many surface types. The USACE National Nonstructural Committee further recommends that the property owner use tapes containing water resistant properties, all-weather properties, brittle resistance, and anti-aging properties. • Closure panels (plywood and other material). A temporary closure system consisting of 1-inch thick plywood or OSB is often recommended for flood barrier construction at doorways and windows; no closure should have a horizontal or vertical span in excess of 3 feet without incorporating additional supports. Because 1-inch paneling may be expensive, a 1-inch closure can be pre-made by using a grid of screws to connect two boards of lesser thickness. Vent openings can usually be protected with a lesser thickness. Do not use materials that are not water resistant. The closure panel should be measured, cut, and identified for the specific location in the temporary flood barrier and should be available for use from one flood season to the next. The panels should be held in place with water resistant caulking, nails, screws and/or liquid nail. For doorways which open inwards, or for over the top of window glass, the closure panel should extend onto the exterior wall. • Sand and Sandbags. Considered to be one of the most durable and easily employed flood-fight products on the market, sandbags are an integral component of many temporary barriers to flooding. Sandbags should be made of nylon or polyethylene. Generally, bags can be placed in a single row up to 3 bags high. Berms more than 3 bags high should be built in pyramid fashion; these berms should be as many bags- wide at the base as they are bags-high. Bags should be filled between half-way and
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two-thirds full, should not be tied and should be placed with the top of the bag tucked under the bag. After placement of each layer, the bags should be walked on to provide a better seal with adjacent bags. The bags in each course should be placed so that they cover to the maximum possible extent the joints in between the bags in the same course and also between the bags in the course below. Additional guidance on sandbagging is available from the Corps of Engineers. Sandbag closures at doorways and similar openings can work well but must be carefully sealed at the ends. The owner may prefer to use a plywood or other type closure panel. • Caulk and Clear Sealant for Structure Exterior. If any portion of the building to be protected consists of brick, stone, stucco, concrete, cinder block, or tile, a water resistant sealant may be recommended for use. The USACE National Nonstructural Committee recommends the property owner use a clear liquid sealant which may be applied by brush, roller, or sprayer. The sealant should be applied to all porous surfaces, which have been thoroughly cleaned and dried to allow deep penetration and maximum resistance to the effects of water. The sealant should be extended above the area of proposed protection for best coverage. While at this time, no government testing programs have rated these commercial sealants, manufacturer’s information indicate that commercial sealants may last up to 20 years without discoloration. In addition, if large cracks and voids in the building exterior need to be filled; many products carried by local hardware companies are compatible with the materials on the exterior of the buildings. • Certified Temporary Flood Barriers. Preventing floodwaters from entering a building requires the use of temporary flood barriers. While there are many products marketed as flood barriers, very few have positively tested and been certified for preventing damages. The Association of State Flood Plain Managers (ASFPM) in collaboration with FM Approvals and the USACE National Nonstructural Committee have implemented a national program of testing and certifying flood barrier products (web page: http://nationalfloodbarrier.org/) used for flood proofing and flood fighting. The purpose of this program is to provide an unbiased process of evaluating products in terms of resistance to water forces, material properties, and consistency of product manufacturing. This is accomplished by testing the product against water related forces in a laboratory setting, testing the product against material forces in a laboratory setting, and periodic inspection of the product manufacturing process for consistency of product relative to the particular product that received the original water and material testing. Upon products meeting the consistency of manufacturing criteria and meeting the established standards for the material and water testing, the certification part of the program becomes available to the product. Since the testing part of the program is conducted in a laboratory setting, not all forces and impacts to which the product could be subjected to during an actual flood event will be tested. Certification will also reflect, in terms of flood proofing, the suitability of the product, the performance of the product based on the product deployment literature, the durability and reliability of the product, and the consistency of the product. All products will be examined and evaluated on a model by model, type by type, plant by plant, and manufacturer by manufacturer basis. For additional information on this program and a list of certified products, visit http://nationalfloodbarrier.org/. • Interior Drainage Pump and Power Supply. In order to prevent flood damages due to seepage of floodwaters through the temporary flood barrier or resulting from a rising water table, it may be recommended that pumps be incorporated into the protection measures. Pumps will be needed inside the building to collect seepage. At a minimum, one pump with a capacity of at least 20 gallons per minute should be considered for installation in the building for every 2,000 square feet of floor space. 115-volt AC powered pumps can be used provided electricity is available throughout the flood event. The owner may consider installing a permanent sump pump with sump pit, or can bring in one or more pumps for temporary use. If loss of electrical power during a flood is a concern, the owner could employ a gasoline-powered electric generator to power the AC pump, or could use one or more battery-powered sump pumps. The user will have to be aware that the battery life is limited; therefore, a spare battery should be kept on-hand. The life of the battery recommended in the battery powered
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back-up sump pump 10 to 14.5 hours of pump use. Because how long a pump will be operating is unknown, the user will need to monitor the pump often and be prepared to replace the battery. If there is no basement or crawl space, the owner may elect to use a floor-type pump that can maintain the depth of water on the floor to 1/8 inch. If the building being protected does have a basement or crawlspace, the pump needs to be placed at the lowest elevation in order to work most efficiently. In some instances the owner may consider cutting a small hole through the floor of a closet space, for concealment purposes, and lowering the pump to the lower level. For a building having a slab on grade structure, the pump should be placed in a location upon the floor where floodwaters may begin to collect. In all cases, the owner should consider placing the pump at a location where the discharge hose is easily positioned to extend beyond the limits of the protection measures. The discharge side of the pump should be sized to match a common 1-inch diameter garden hose or should be equipped with an adaptor to 1 inch. If there is a sandbag berm, a pump with significant capacity will be needed to collect rainfall, seepage and rising groundwater within the area of the berm.
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5.0. Nonstructural Assessment Objectives The study area of the nonstructural assessment has buildings which are generally classified as residential or commercial. For a nonstructural assessment, each building must be investigated for purposes of determining what type of flood risk adaptive measure is most appropriate for that particular building depending on what architects constructed within the wall and or foundation structure, where the building is located within the floodplain, what the local flood characteristics are (velocities, stages, and duration), and other site conditions (soil, permeability, vegetation). A 1% annual chance exceedance flood was considered as the benchmark for implementation of nonstructural measures to mitigate the flood risk. The team had the building information visible from the outside, which they collected in the field during the land survey. Assessment objectives included determination of the appropriate nonstructural technique for each building. Several considerations were required to determine if the nonstructural measures considered would be appropriate for a given building. In particular, the building had to be in relatively good condition, i.e., had to be structurally sound, in order to withstand elevation, relocation, or flood proofing. If the building was in poor condition, then only filling in the basement/crawlspace, if one existed, was considered, without investigating elevation, relocation, or dry flood proofing. Also, there needed to be adequate room around the building to maneuver the necessary equipment if elevation was the designated nonstructural technique. Filling in the basement/crawlspace includes relocating utilities, mechanical equipment (furnace, water heater, water softener, and appliances), electrical panels and circuits, as well as some storage to a new location above the base flood elevation. These measures were considered because they would both reduce future flood damages to the building’s structure and reduce flood insurance premiums for the owner, which start at the lowest habitable elevation. For dry flood proofing, the depth of flooding has to be limited to between three to four feet above ground elevation and the walls of the building have to be of such structural integrity as to being able to withstand the lateral forces applied by the floodwaters. Relocation is considered if the depth of flooding is determined to be greater than 12-feet, where if the depth at the building is greater than 12-feet the project team would require the building to be elevated to such a height the property owner regards as unreasonable to inhabit, to place first responders at risk, or the costs to elevate may significantly increase due to the need for structural stability to resist wind forces on the elevated building. The assessment shows a significant number of at risk structures located throughout the area, when considered under the two scenarios. Most of the structures have been constructed during a period of time ranging from the early 1800’s through the 1900’s. While most of the commercial buildings appear to have been constructed at ground or street level elevation, the residential buildings vary in the first floor height off of the ground depending upon the style of the structure and whether a crawlspace or basement were contained within the structure. The size of buildings also varied greatly from single story to multi-story for residential buildings and from individual stand-alone to multi-bay commercial buildings. Many of the commercial buildings were constructed as slab-on-grade, with walls being constructed of masonry, metal, and wood.
5.1. Description of Assessment Inventory
For this assessment, information was collected for a sampling of buildings located in Figure 3-1, Florence, KS flood insurance map (effective March 2011) shown with land survey points. This resulted in 264 buildings being assessed. The project team collected additional building data from the county assessor database from the Marion County. Additional information was collected during the land survey.
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Also, the team used photography from GoogleStreet View. USACE Tulsa District developed the depths of flooding. The USACE Kansas City District collected a limited land survey including just ground and finished floor elevations adjacent to buildings (see section Land Survey). The assessment conducted was reconnaissance level in detail. If mitigation could occur on an individual building, additional detailed data would be required. For the current level of assessment, the data is sufficient to identify potential nonstructural measures which could be effective in reducing future flood risk, life loss and property damage. A list of buildings assessed is provided in the tables in the section, Recommendation of Nonstructural Flood Risk Adaptive Measures.
5.2. Description of Nonstructural Assessment
A member of the USACE National Nonstructural Committee and personnel from USACE-Kansas City District conducted a site visit followed by an office assessment for each of the 264 buildings. The field visit allowed the USACE team to observe each building from the exterior/interior and to reaffirm the data collected for each individual building. Building and site conditions, as well as flood elevations are compiled with field observations onto building data/assessment sheets, when full cost benefit analysis is part of the project’s scope. The compiled information on the building data/assessment sheets helps to demonstrate the potential flood risk and can be used to identify potential nonstructural measures for implementation. The base flood elevation (1% annual exceedance flood elevation) was targeted for mitigation recommendations. Each building was assessed using a similar format. The assessments and recommendations focused on mitigating buildings utilizing elevation, dry flood proofing, wet flood proofing, or relocation/acquisition. Nonstructural flood risk adaptive measures which would be compliant with the National Flood Insurance Program and would reduce flood insurance premiums for the property owner were primarily considered. The nonstructural measures presented in this report are stand-alone mitigation techniques for individual buildings or combination techniques to provide the most effective level of flood risk reduction. The following observations and assumptions were incorporated into the assessment because of the reconnaissance level of detail: 1. Basement utilities, equipment and storage are proposed to be relocated to existing space or an addition to the existing building and above the mitigation flood elevation. A more detailed investigation would be required to determine the specific area to accommodate these items. 2. Inventory data adjusted based on field observations. 3. Dry flood proofing was limited to four-feet in height unless the building appeared to have the structural integrity to be capable of withstanding greater forces.
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4. If the flood elevation is greater than the first floor elevation and a basement/crawlspace exists, the first floor cannot be dry flood proofed without eliminating the basement/crawlspace. For residential 5. Common flood mitigation actions should always evaluate the need structures dry flood for flood openings, anchoring various utilities that could be moved proofing will require due to buoyancy, and other considerations, and these are included as part of this nonstructural assessment. This is intended to assist filling in the basement the community in addressing needed public safety, to be in when a structure has a accordance with floodplain ordinances, and to ultimately help basement. comply with the FEMA NFIP. 6. Wet flood proofing is generally possible in all situations. Sometimes a reason exists to make this second to a measure that offers a better opportunity and when another deficiency needs to be addressed. 7. For the screening of nonstructural measures in Florence, Kansas, the project team assumed the flooding is with low velocities in the leveed area. The soils also affect flood risks, although in Florence, these soils are generally impermeable and lowers the risk of flooding due to groundwater.
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6.0. Risk Management Options Recommendations Within this section, the stakeholders get an in-depth analysis of the full menu of measures. This full menu includes activities that may be done as well as features that can be built. In this case with Florence, Kansas, the community’s unique selection of measures includes the levee. This section presents the findings, where the full menu of flood risk management measures is narrowed down to a short list of risk management options to help the city and property owners select their specific mitigation actions. These are specific to help address residual flooding behind the levee. The analysis is based upon the data collected for the 264 assessed buildings and the potential depth of flooding for the 1% annual The levee reduces chance exceedance flood event. Some minor, additional information flood risk but does regarding some costs associated with the recommended nonstructural technique for each of the assessed buildings is not eliminate it. provided in appendices. This risk assessment focuses on at-risk buildings and contains the detailed technical assessment used for investigating the incorporation of measures in the community. This report’s most significant outcome is getting all stakeholders to realize the importance of combining measures to reduce flood risk, because the levee reduces flood risk but does not eliminate it. Whether or not the levee is certified, the flooding still can occur. Whether hydrologic conditions remain the same or increase in the future, all buildings located within the vicinity of the assessment area are at risk of flooding. Those at the local level are responsible for taking any additional actions to manage this flood risk. The parties responsible range from the city staff to property owners. Flood risk management is a shared responsibility. This section presents information for both city staff and property owners, so they can understand the smaller set of risk management options and form their approach in their own action plan. Another valuable resource is the publication So, You Live Behind a Levee! (American Society of Civil Engineers (ASCE), 2010). This is available online. The publication provides further descriptions of a variety of elements that property owners should know when owning land in the leveed area. The source of the most major historic floods in the assessment area is significant rainfall within the watersheds being conveyed along the Cottonwood River and Doyle Creek, as well as the interior drainage watershed for the leveed area. The typical time element for significant stage increase from rainfall runoff, flood warning is generally adequate to enable human intervention to reduce flood damages from occurring to most personal property by implementing closures or evacuating some valuables. The depth of flooding is generally shallow and with low velocities in the leveed area. The soils also affect flood risks, although in Florence, these soils are generally impermeable and lowers the risk of flooding due to groundwater. The floodplain located within the Florence area consists of residential, commercial, and public development. Basements and crawl spaces exist in some of the buildings. Many manufactured homes are present. Age of development is from very old to relatively new. The measures recommended have narrowed the list of measures. Considerations use the unique characteristics of each property from the land survey information. Finally, the report presents these findings in two tiers of recommended measures.
This report’s most significant outcome is getting all stakeholders to realize the importance of combining measures to reduce flood risk…
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6.1. Tier 1, Flood Risk Management Options for the Overall Community
This section presents one tier, including the first, second, and third measures, which are broad and are about the overall community. These are presented as the Tier 1 risk management options in the first table below. They presume the community continues to maintain and operate the levee and also stays eligible in the flood insurance program. However, property owners must also actively engage, specifically in assuming their role in applying for and paying flood insurance premiums.
Table 6-1. Tier 1 Recommended Priority Risk Management Options for All Scenarios and Broad Community Actions.
Emergency Action High Priority Measures Flood Insurance Flood Warning Planning
6.1.1. Tier 1, Flood Insurance
The project team recommends flood insurance as the number one most useful risk management option for Florence. For almost 50 years, the National Flood Insurance Program, as managed by FEMA, has provided coverage for property owners concerned about flooding. For the overall community, the first measure, flood insurance, is an under-used measure, and both the community staff and property owners must take action. Property owners have trouble understanding that flood insurance is not part of any home owner insurance. Flood insurance is separate from home owner’s insurance, but anyone may ask their insurance provider for this coverage. One startling statistic is that home owners accept the fact they have a risk of house fires, and they have that in their home owner insurance. Flood insurance is separate, as this is a federally subsidized program, but few home owners take action to get flood insurance. • Property owners should learn more on the Federal Emergency Management Agency, National Flood Insurance Program, which is available at this web link below. https://www.floodsmart.gov/ Whether or not the Florence levee is certified, the properties will benefit from flood insurance. Flood insurance premiums can be lowered by some measures. One particularly helpful measure is elevating the building (see below). Communities, like Florence, participating in the NFIP Community Rating System (CRS) can reduce flood insurance premiums by over 40% when scoring points in all the CRS activities.
The project team recommends flood insurance as the number one most useful risk management option for Florence.
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The Florence participates in the NFIP, so flood insurance is available for all buildings in the community regardless of their flood zone designation. The community also participates in the NFIP’s Community Rating System (CRS). The CRS activities are optional, but the more activities the city does, the lower the flood insurance premiums will be for anyone in the community, regardless of whether they are in the special flood hazard area. Preferred risk flood insurance policies, which are relatively inexpensive, may be available for buildings located outside of the FEMA “Zone A” designated areas shown on the effective FIRM. Implementation of nonstructural measures may result in reduced flood insurance premiums under the NFIP for certain building type. Insurance premiums for buildings located within the special flood hazard area are functions of the elevation of the first floor of the building (which may be a Figure 6-1. In floodplains, the risk of flooding is five times basement or crawlspace, if either exists) greater than fire (ASCE, So, You Live Behind a Levee!). with respect to the BFE. The lowest floor elevation, which for properties with basements is the top surface of the basement floor, will dictate the premium rate for flood insurance. The property owners should be familiar with these details from the FEMA web site www.floodsmart.gov. For residential buildings, elevation of the building on an extended foundation wall, on fill material, piers, posts, and columns has the effect of reducing the flood insurance premium because the building is being moved away from the flood risk. The USACE National Nonstructural Committee and project team emphasize that flood insurance is based upon a single flood event, the 1% annual chance exceedance flood …the top surface of event and not a range of flood events. If the residential building is the basement floor, will elevated to be above the 1% flood elevation, there is still a possibility dictate the premium that a larger, more infrequent flood event could occur. Figure 6-2 illustrates the potential reduction in flood insurance premium for a rate for flood sample residential building elevated on extended foundation walls. insurance. Currently, with regards to residential buildings, no other physical nonstructural measure, other than acquisition and relocation of the building, provides a benefit by reducing the flood insurance premium. While wet flood proofing and dry flood proofing a residential building have the potential to reduce property damages associated with flooding, neither technique results in a reduction in insurance premiums. As of the date of this report, FEMA had been directed by Congress, under the Homeowner Flood Insurance Affordability Act of 2014 (HIFAA), to produce guidelines for property owners regarding alternative mitigation efforts, other than building elevation, to reduce flood risk to residential buildings that cannot be elevated due to structural characteristics. This request requires alternative forms of mitigation measures to be considered in the calculation of risk premium rates. However, for nonstructural mitigation of commercial buildings, a reduction in flood insurance premium may be obtainable if the flood risk for an individual building can be reduced through mitigation such as elevation or dry flood proofing. As discussed in Section 5.4.11, dry flood proofing is the prevention of floodwaters from entering a commercial building through implementation of engineered systems.
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Figure 6-2. Flood Insurance Premium Reduction through Elevation.
6.1.2. Tier 1, Emergency Action Planning While the City of Florence has an emergency action plan (EAP), dated February 15, 2008, the EAP needs to properly address the hazard of flooding. Many other hazards, such as tornadoes, are well addressed. The USACE-Tulsa District noted in the inspection report, Flood Damage Reduction Project, Periodic Inspection (May 17, 2010), that an EAP is needed. Under the section on operation and maintenance items, one of three notes stated the following:
A written emergency action plan defining responsibilities and procedures for actions to be taken in the event of an actual or potential emergency condition, including evacuation plans should be prepared in accordance with USACE guidance and distributed to all parties involved in emergency response. Tier 1 risk management options calls the community’s attention to the EAP again. The project team recommends that the community emergency managers address the following elements: • The hazard section, Flood, has no text at all. The section needs to address the remaining bullets that follow. • The lowest elevation on the levee is 1077.7 (USACE National Levee Database, levee profile) and needs to noted in the EAP. The elevation is important information to know prior to high water on the river.
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• The emergency manager should watch the nearest gages, and two federal partners provide useful information. The U.S. Geological Survey helps operate and maintain stream gages. The NOAA National Weather Service (NWS) forecasts flood stages for these gages. The nearest gage for Florence, Kansas is the Cottonwood River Near Florence (FLRK1) and is on the web site below. Under the Flood Impacts section of the web page, river stage 48 is described as follows:
The southern section of the levee system around the city of Florence may become breeched. If levee is overtopped, flood waters may rise up to four feet deep across most of the city streets of Florence. Expect dozens of homes to be flooded.
o NOAA National Weather Service, Advanced Hydrologic Prediction Service https://water.weather.gov
o NOAA National Weather Service, Advanced Hydrologic Prediction Service, Cottonwood River Near Florence (FLRK1): https://water.weather.gov/ahps2/hydrograph.php?wfo=ict&gage=flrk1 • The USACE-Tulsa District operates and maintains the Marion Lake upstream on the Cottonwood River and has operation personal available 24 hours a day seven days a week. The Lake Manager and staff can communicate more information about floodwater releases. The project team suggests that the real-time status of Marion Lake, given in the web site below, be available in the EAP.
o USACE-Tulsa District at Marion Lake http://www.swt-wc.usace.army.mil/MARI.lakepage.html • The EAP does not describe the reverse 911 system noted in the USACE National Levee Database’s (NLD) Risk Characterization section. The redundant notifications, through radio, and door-to-door, are also described. The EAP could be improved by describing what public radio stations are involved, including their phone numbers. The door-to-door process should prioritize the lowest locations and those closest to the lowest points in the levee profile (available in the USACE NLD levee profile). Also, all these information techniques should tie a warning threshold that ties to flood stages (see the section below, Flood Warning). • The emergency managers should develop public messages for the EAP describing where to go, prior to a disaster. They also should consider pre-identifying zones with boundaries determined by streets and targeting specific messages on which way to evacuate. The city could keep this simple and use as few as two or three zones separated using cross streets like 5th Street and Main Street.
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• Shelters are identified as the two churches in the community, however, both are located in the potential flood limits inside the leveed area should the levee fail and or overtop. While the shelters are important for other natural hazards in the current EAP, different evacuation locations besides these churches are needed for the flood hazard. “…flood waters • The emergency managers should identify an evacuation may rise up to location on the west or northwest side of the city that is above the 1078 elevation, and this is generally west of Doyle Street. four feet deep • The EAP identifies the emergency operation center (EOC) at across most of the city office at 5th Street and Main Street, however, in the event of a levee overtopping, that location will be flooded up the city streets of to six feet deep. The EAP should select a different EOC, west Florence. Expect of Doyle Street and higher than the lowest point on the levee, elevation 1077.7 (per NLD levee profile). dozens of homes For the emergency action planning and flood warning, the community to be flooded.” staff can look at these resources to greatly enhance their flood risk management: • USACE Guidance for Emergency Action Plans, Incident Management and Reporting, and Inundation Maps for Dams and Levee Systems • USACE-St. Paul District Emergency Action Plan Guide http://www.mvs.usace.army.mil/Portals/54/docs/emergencymanagement/EAP_Combined_Ver1.1 _Jan15_1.pdf Both references may help the city and Marion County staff to further enhance the current Florence emergency action plan. EAPs play a vital role in comprehensive risk management for USACE dam and levee projects. USACE Guidance for Emergency Action Plans, Incident Management and Reporting, and Inundation Maps for Dams and Levee Systems says:
“An EAP is a formal document that identifies potential emergency conditions at a project and specifies pre-planned actions to be followed to reduce consequences of the emergency. An EAP is prepared by the owner/operator of a dam or levee project stressing the actions to take to moderate or alleviate the emergency.” The USACE requirement is intended to urge levee owners and sponsors to create standardized EAPs. USACE is publically sharing the document and assorted tools to assist stakeholders in developing or updating their EAPs. Along with sections for incident management and reporting, inundation maps for dams and levee systems are also covered, and a series of links to further public information is gathered in Appendix A of the guidance document. The USACE Planning Toolbox helps answer questions about the guidance document in a webinar, held June 21, 2018, a follow-up Q and A summary covers some of the critical questions on the document. One question about developing EAPs explains why some EAP guidebooks are helpful and why the EC is not prescriptive about a template EAP.
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6.1.3. Tier 1, Flood Warning Tier 1 risk management options may enhance the community’s emergency action plan by tying their plan to flood warning tools. Very specifically, the current Florence 911 calling tool. In addition, the public and city staff can subscribe to alerts at this web page: https://water.usgs.gov/wateralert/subscribe2/.
Figure 6-3. USGS gage alerts come to any applicant for free using this subscription web site.
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Figure 6-4. The emergency managers can use forecasted stages from NOAA National Weather Service as a flood warning tool to take action per their emergency action plan.
Community officials, including the city and county, should consider tailoring public messages to specific areas behind the Florence levee. See the previous section of this report for more details on improving that within the EAP. These resources will aid in developing flood warning messages. • USACE A Guide To Public Alerts and Warnings for Dam and Levee Emergencies https://silverjackets.nfrmp.us/Portals/0/doc/Missouri/150605%20WarningGuidebook_USACE%2 0Drs%20Sorensen%20Mileti.pdf?ver=2018-08-01-144347-333 • NOAA National Weather Service, Advanced Hydrologic Prediction Service, Cottonwood River Near Florence (FLRK1): https://water.weather.gov/ahps2/hydrograph.php?wfo=ict&gage=flrk1
6.2. Tier 2, Flood Risk Management Options for the Property Owners
A second tier of priorities further helps to define specific mitigation actions that the community’s property owners should consider. Based on specific details at each property, as found with land survey data, the project team has recommended three additional risk management options in the next table on the following pages. Property owners should combine these with the levee to diversify their defense against
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flooding. Once again the point numbers are provided, as referred to the land survey points collected in the section, Land Survey. For a community using a levee and considering other additional flood risk management options, the buyout is considered a last resort, although buyout or acquisition is a valuable re-development option, Property owners and the community should still want to consider the context of the residual risk of flooding with the levee. Compared to the tradeoffs, should combine buyouts are generally the preferred measure for those outside of these with the community, looking in, because of the reduced need for emergency rescues and the possibility to reduce public services to an area, such levee to diversify as water and sewer. However, this project's nonstructural assessment first offers the alternatives that those living on the residential sites their defense wish to better understand prior to accepting a more sweeping buyout against flooding. assumption. For commercial sites, while large masonry or brick buildings could be relocated, the cost to do so is most likely unaffordable for rural communities that are have little or no economic growth. The recommendations come from a list of Tier 2 risk management options, recognizing only a few of these are appropriate for each property based on the unique, geographic conditions. See definitions in the glossary in the appendix. • No action • Dry flood proofing • Wet flood proofing • Elevation on foundation walls
o Elevate utilities • Elevation on piers o Anchor storage tanks • Elevation on fill o Anchor mobile homes • Relocation • Flood openings • Buyout / acquisition • Fill basement The project team recognized the following geographic conditions at each property and screened most of the items above to narrow the list. Conditions included the building foundation as one of the following. • Slab on grade • Crawl space • Basement And possible type of building’s construction material is below. • Concrete or masonry • Metal • Wood
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Table 6-2. Tier 2 Recommended Risk Management Options for the Primary Scenario for Mitigation Actions at Specific Properties. ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure 1 101 DOYLE Flood Vents Elevation on Wet Flood Foundation Walls Proofing 2 110 DOYLE Flood Vents Wet Flood Buyout / Proofing Acquisition
3 Railroad Depot No Action
4 311 W 2ND Flood Vents Wet Flood Relocation Proofing 5 304 W 2ND Flood Vents Wet Flood Elevation on Proofing Foundation Walls
6 236 W 2ND Buyout / Acquisition 7 222 W 2ND Flood Vents Elevation on Wet Flood Foundation Walls Proofing 8 212 W 2ND Helical Ground Elevation on Piers Buyout / Anchoring Acquisition
9 311 W 2ND Flood Vents Elevation on Wet Flood Foundation Walls Proofing
10 311 W 2ND Relocation Elevation on Piers 11 223 W 2ND Flood Vents Elevation on Relocation Foundation Walls
12 213 W 2ND Wet Flood Buyout / Proofing Acquisition 13 310 W 3RD Dry Flood Proofing Wet Flood Relocation Proofing 14 302 W 3RD Flood Vents Elevation on Relocation Foundation Walls 15 218 W 3RD Dry Flood Proofing Wet Flood Relocation Proofing
16 214 W 3RD Dry Flood Proofing Wet Flood Relocation Proofing
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure 17 234 MARION Dry Flood Proofing Wet Flood Relocation Proofing
18 223 MAIN Flood Vents Wet Flood Buyout / Proofing Acquisition
19 unused point
U.S. Post Office 20 302 MAIN Wet Flood Buyout / Proofing Acquisition
21 323 W 3RD Flood Vents Elevation on Wet Flood Foundation Walls Proofing
22 301 DOYLE Wet Flood Buyout / Proofing Acquisition 23 229 W 3RD Helical Ground Elevation on Piers Buyout / Anchoring Acquisition
24 229 W 3RD
25 209 W 3RD Wet Flood Buyout / Proofing Acquisition
26 201 W 3RD Buyout / Acquisition 27 308 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls 28 304 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
29 129 W 3RD Wet Flood Elevation on Proofing Foundation Walls
30 125 W 3RD Buyout / Acquisition 31 107 W 3RD Helical Ground Elevation on Piers Buyout / Anchoring Acquisition
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure 32 310 MAIN Wet Flood Elevation on Relocation Proofing Foundation Walls
33 103 E 3RD Flood Vents Elevation on Wet Flood Foundation Walls Proofing
34 315 MAIN Wet Flood Buyout / Proofing Acquisition 35 302 W 4TH Elevation on Dry Flood Proofing Wet Flood Foundation Walls Proofing 36 234 W 4TH Flood Vents Elevation on Wet Flood Foundation Walls Proofing
37 230 W 4TH Elevation on Wet Flood Relocation Foundation Walls Proofing
38 210 W 4TH Flood Vents Elevation on Wet Flood Foundation Walls Proofing
39 204 W 4TH Wet Flood Elevation on Proofing Foundation Walls
40 120 W 4TH Wet Flood Elevation on Proofing Foundation Walls
41 108 W 4TH Wet Flood Elevation on Proofing Foundation Walls 42 104 W 4TH Helical Ground Elevation on Piers Buyout / Anchoring Acquisition
43 321 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
Public Library 44 324 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
Fire Department
45 100 E 4TH Wet Flood Elevation on Relocation Proofing Foundation Walls
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure
City Hall 46 100 E 4TH Wet Flood Elevation on Relocation Proofing Foundation Walls 47 403 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
Main Park
48 unused point
49 405 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls 50 235 W 4TH Elevation on Wet Flood Relocation Foundation Walls Proofing
51 225 W 4TH No Action
52 209 W 4TH Flood Vents Dry Flood Proofing Wet Flood Proofing
53 407 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls 54 203 W 4TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls 55 121 W 4TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
56 117 E 4TH Helical Ground Elevation on Piers Relocation Anchoring
57 119 W 4TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure
58 unused point
59 unused point
60 409 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
61 105 W 4TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
62 101 W 4TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls 63 410 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
64 411 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
65 412 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
66 unused point 67 413 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
68 411 BARKER Flood Vents Wet Flood Elevation on Piers Proofing
69 205 E 4TH Flood Vents Elevation on Wet Flood Foundation Walls Proofing
70 217 E 4TH Flood Vents Buyout / Acquisition
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure 71 415 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
72 unused point 73 416 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
74 417 MAIN Flood Vents Wet Flood Elevation on Proofing Foundation Walls
75 234 W 5TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
76 419 MAIN Flood Vents Wet Flood Elevation on Proofing Foundation Walls 77 202 W 5TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
78 124 W 5TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
79 122 W 5TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
80 104 W 5TH Elevation on Wet Flood Relocation Foundation Walls Proofing 81 423 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls 82 424 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls 83 114 E 5TH Wet Flood Elevation on Relocation Proofing Foundation Walls
84 124 E 5TH Wet Flood Elevation on Relocation Proofing Foundation Walls
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure 85 410 BARKER Helical Ground Elevation on Piers Relocation Anchoring
86 224 E 5TH Wet Flood Elevation on Relocation Proofing Foundation Walls
87 503 MAIN Wet Flood Elevation on Relocation Proofing Foundation Walls
88 502 MAIN Wet Flood Elevation on Proofing Foundation Walls 89 229 W 5TH Wet Flood Elevation on Relocation Proofing Foundation Walls
90 225 W 5TH Wet Flood Elevation on Relocation Proofing Foundation Walls
91 221 W 5TH Flood Vents Wet Flood Proofing
92 217 W 5TH Flood Vents Wet Flood Proofing
93 215 W 5TH Flood Vents Wet Flood Proofing 94A 507 MAIN Wet Flood Elevation on Buyout / Proofing Foundation Walls Acquisition 94-C 507 MAIN Wet Flood Elevation on Buyout / Proofing Foundation Walls Acquisition
95 400 BARKER ST Buyout / Acquisition 96 201 W 5TH Wet Flood Flood Vents Fill Basement Proofing
97 125 W 5TH Wet Flood Flood Vents Elevation on Proofing Foundation Walls
98 105 W 5TH Wet Flood Flood Vents Elevation on Proofing Foundation Walls 99 105 W 5TH Wet Flood Flood Vents Elevation on Proofing Foundation Walls
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure 100 103 E 5TH Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
101 510 MAIN No Action
102 119 E 5TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
103 509 BARKER Helical Ground Elevation on Piers Anchoring
104 502 BARKER Flood Vents
105 211 E 5TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
106 221 E 5TH Wet Flood Proofing 107 514 MAIN Wet Flood Elevation on Relocation Proofing Foundation Walls
108 236 W 6TH Wet Flood Buyout / Proofing Acquisition
109 228 W 6TH Wet Flood Elevation on Proofing Foundation Walls
City EMTs, Ambulance 110 515 MAIN Wet Flood Elevation on Relocation Proofing Foundation Walls
111 216 W 6TH Wet Flood Elevation on Proofing Foundation Walls
112 216 W 6TH Wet Flood Elevation on Proofing Foundation Walls
113 214 W 6TH Flood Vents Elevation on Foundation Walls
114 210 W 6TH Flood Vents Wet Flood Proofing
115 513 MARION Flood Vents Wet Flood Fill Basement Proofing
116 124 W 6TH Helical Ground Elevation on Piers Wet Flood Anchoring Proofing
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure
117 114 W 6TH Flood Vents Wet Flood Proofing
118 106 W 6TH Wet Flood Elevation on Proofing Foundation Walls
119 521 MAIN Wet Flood Buyout / Elevation on Proofing Acquisition Foundation Walls
120 528 BARKER Flood Vents Wet Flood Elevation on Proofing Foundation Walls
121 217 E 6th ST Wet Flood Buyout / Proofing Acquisition
122 236 E 6TH Wet Flood Buyout / Proofing Acquisition
123 603 MAIN Flood Vents
124 233 W 6TH Flood Vents
125 227 W 6TH Flood Vents Elevation on Foundation Walls
126 225 W 6TH Flood Vents Elevation on Foundation Walls
127 221 W 6TH Flood Vents Elevation on Foundation Walls
128 213 W 6TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
129 601 MARION Wet Flood Elevation on Proofing Foundation Walls 130 605 MARION Flood Vents Wet Flood Elevation on Proofing Foundation Walls 131 604 MAIN Flood Vents Wet Flood Elevation on Proofing Foundation Walls
Unity Park 132 600 W 6TH No Action
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure
Old school 133 111 W 6TH Wet Flood Dry Flood Proofing Proofing 134 609 MAIN Flood Vents Wet Flood Elevation on Proofing Foundation Walls 135 103 E 6TH Flood Vents Wet Flood Buyout / Proofing Acquisition
136 123 E 6TH Wet Flood Proofing 137 201 E 6TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls 138 217 E 6TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls 139 610 MAIN Flood Vents Wet Flood Elevation on Proofing Foundation Walls 140 613 MAIN Flood Vents Wet Flood Elevation on Proofing Foundation Walls 141 225 E 6TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
142 236 W 7TH No Action
143 228 W 7TH No Action
144 222 W 7TH Flood Vents Wet Flood Proofing
145 unused point 146 208 W 7TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls 147 624 MARION Helical Ground Elevation on Piers Wet Flood Anchoring Proofing
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure
148 130 W 7TH Flood Vents Wet Flood Proofing
149 128 W 7TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
150 108 W 7TH Flood Vents Wet Flood Proofing
151 104 W 7TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls 152 623 MAIN Flood Vents Wet Flood Fill Basement Proofing
153 624 MAIN Flood Vents Wet Flood Fill Basement Proofing
154 114 E 7TH Helical Ground Wet Flood Anchoring Proofing
155 620 BARKER Helical Ground Wet Flood Anchoring Proofing
156 unused point 157 236 E 7TH Wet Flood Elevation on Proofing Foundation Walls 158 703 MAIN Flood Vents Wet Flood Elevation on Proofing Foundation Walls
159 235 W 7TH No Action
160 229 W 7TH No Action
161 225 W 7TH Flood Vents Wet Flood Proofing 162 223 W 7TH Flood Vents Wet Flood Fill Basement Proofing
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure
163 133 W 7TH Wet Flood Elevation on Proofing Foundation Walls
164 106 E 7TH
165 131 W 7TH Flood Vents Wet Flood Proofing
166 127 W 7TH Flood Vents Wet Flood Fill Basement Proofing 167 123 W 7TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
168 105 W 7TH Wet Flood Elevation on Proofing Foundation Walls
169 103 W 7TH Flood Vents Wet Flood Proofing
170 711 MAIN Flood Vents Wet Flood Proofing
171 117 E 7TH Helical Ground Wet Flood Anchoring Proofing
172 235 E 7TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
173 714 MAIN Buyout / Acquisition
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure
174 715 MAIN Buyout / Acquisition
175 236 W 8TH No Action
176 226 W 8TH Wet Flood Proofing
177 218 W 8TH Flood Vents Wet Flood Proofing
178 210 W 8TH Flood Vents Wet Flood Fill Basement Proofing
179 202 W 8TH Flood Vents Wet Flood Proofing 180 726 MARION Flood Vents Wet Flood Fill Basement Proofing 181 112 W 8TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
182 108 W 8TH Flood Vents Wet Flood Proofing 183 721 MAIN Flood Vents Wet Flood Elevation on Proofing Foundation Walls 184 106 E 8TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
185 721 BARKER Flood Vents Wet Flood Elevation on Proofing Foundation Walls
186 unused point
187 107 W 8TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
188 unused point
189 809 MAIN Flood Vents Wet Flood Proofing
190 810 MAIN Flood Vents Wet Flood Proofing
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure
191 815 MAIN Flood Vents Wet Flood Proofing
192 810 BARKER Flood Vents Wet Flood Elevation on Proofing Foundation Walls
193 818 MAIN Flood Vents Wet Flood Elevation on Proofing Foundation Walls
194 231 W 8TH Flood Vents Wet Flood Proofing
195 834 MARION Flood Vents Wet Flood Proofing
196 110 W 9TH Wet Flood Proofing 197 203 W 8TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
198 817 MAIN Flood Vents Wet Flood Proofing 199 201 W 8TH Flood Vents Wet Flood Fill Basement Proofing
200 822 MAIN Helical Ground Wet Flood Elevation on Piers Anchoring Proofing
Public Housing (HUD) 201 102 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls
201-1 102 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls 201-2 102 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls 201-3 102 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls 201-4 102 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure 201-5 102 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls 201-6 102 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls 201-7 102 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls 201-8 102 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls 202 905 MARION Flood Vents Wet Flood Elevation on Proofing Foundation Walls
203 911 MARION Flood Vents Wet Flood Proofing
204 901 MAIN Flood Vents Wet Flood Elevation on Proofing Foundation Walls
205 unused point 206 913 MARION Flood Vents Wet Flood Elevation on Proofing Foundation Walls 207 103 E 9TH Helical Ground Wet Flood Elevation on Piers Anchoring Proofing
208 210 W 10TH No Action
209 206 W 10TH No Action
210 915 MARION Flood Vents Wet Flood Proofing 211 914 MAIN Flood Vents Wet Flood Elevation on Proofing Foundation Walls
212 103 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls
213 unused point
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure
Public Housing (HUD) 214 109 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls
214-1 109 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls 214-2 109 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls 214-3 109 E 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls
215 1007 MARION Flood Vents Wet Flood Proofing
216 1003 MARION Flood Vents Wet Flood Fill Basement Proofing
217 209 W 10TH No Action
218 209 W 10TH No Action
219 1011 MARION Flood Vents Wet Flood Fill Basement Proofing 220 1012 MARION Flood Vents Wet Flood Fill Basement Proofing
221 109 W 9TH Wet Flood Elevation on Relocation Proofing Foundation Walls
222 1015 MARION No Action
223 206 W 11TH No Action
224 1023 MARION No Action
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure 225 1101 MAIN Wet Flood Elevation on Relocation Proofing Foundation Walls 226 1027 MARION Wet Flood Elevation on Relocation Proofing Foundation Walls
227 1300 MARION No Action
228 326 W 4TH Wet Flood Proofing
229 213 W 4TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls 230 PUBLIC ROAD Flood Vents Wet Flood Elevation on Proofing Foundation Walls
231 233 W 10th No Action
232 511 main Wet Flood Elevation on Relocation Proofing Foundation Walls 233 Doyle street Flood Vents Wet Flood Fill Basement Proofing
234 220 W 10TH ST No Action
235 234 W 10th No Action
236 238 w 10th No Action
237 238 w 10th No Action
238-299 unused points 300 232 w 4th street Flood Vents Wet Flood Proofing 301 230 w 4th street Flood Vents Wet Flood Elevation on Proofing Foundation Walls 302 303 w 4th street Wet Flood Elevation on Relocation Proofing Foundation Walls
303 313 w 4th street Flood Vents Wet Flood Proofing
304 Mid Kansas No Action Cooperative
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ID# Address 4th Nonstructural 5th Nonstructural 6th Nonstructural Measure Measure Measure
305 Mid Kansas No Action Cooperative
306 Mid Kansas No Action Cooperative 307 Mid Kansas Flood Vents Wet Flood Dry Flood Proofing Cooperative Proofing 308 501 DOYLE Wet Flood Dry Flood Proofing Elevation on Proofing Foundation Walls
309 415 DOYLE Wet Flood Proofing
310 413 DOYLE Flood Vents Wet Flood Proofing 311 521 DOYLE Wet Flood Elevation on Relocation Proofing Foundation Walls
312 601 DOYLE Flood Vents
313 621 DOYLE No Action
314 726 MARION Buyout / Acquisition
315 302 W 8TH No Action
316 300 W 8TH No Action
317 298 W 8TH No Action
318 210 W 8TH Flood Vents Wet Flood Elevation on Proofing Foundation Walls
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6.3. Tier 2, Detailed Explanation of Risk Management Options
This section offers further explanations of the risk management options for various property level situations. The figures present the measures with relation to the 1% annual chance exceedance flood level use in the National Flood Insurance Program (NFIP), or base flood elevation, and the lowest adjacent grade to help explain the existing condition. The proposed mitigation solutions, or risk management options, also reflect the base flood and lowest adjacent grade. Some existing conditions have more than one proposed mitigation measure. The property owners should remember that the Secondary Scenario, or levee overtopping, is another possible flooding scenario. This is a reminder that flooding is a continuum, so preparing for more severe events, which may be less frequent, but possible, is a good idea. 6.3.1. Tier 2, Risk Management Options for Utilities Many properties can significantly reduce the risk of damaged utilities. Property owners can have air conditioners, fans, electrical boxes, water heaters, and even kitchen appliances elevated to levels that floodwaters seldom reach. This risk management option is easily combined with other measures to create a resilient property.
Figure 6-5. A Florence, Kansas property with the air conditioner already elevated.
6.3.2. Tier 2, Risk Management Options Using Flood Openings in Foundations Any building with a basement or a crawl space will see uneven stress applied to the foundation when floodwaters are present. This pressure on the outside can often crack foundations and cause structural failures. A relatively inexpensive risk management option is to have a contractor install flood openings and flood vents (or flood louvers). This means the basement or crawlspace will have floodwater allowed inside, but the tradeoff of losing that space is saving against costly foundation repairs.
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6.3.3. Tier 2, Risk Management Option for Basement Flooding For properties where basements exists, property owners may consider the figures in this section to better visualize the measures.
Figure 6-6. Existing condition building with a basement that floods.
Proposed risk management option for flooding basement can be done with different approaches, although the property owner needs to keep in mind how the flood insurance premium takes into account the lowest level inside the building. If flood insurance is not part of the diverse set of mitigation actions a property owner uses, then other variations can address the basement.
Figure 6-7. Example home in Florence with basement windows.
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Figure 6-8. Proposed risk management option: Elevation on foundation walls.
Figure 6-9. Proposed risk management option: Wet flood proofing.
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Figure 6-10. Proposed risk management option: Dry flood proofing and fill basement.
6.3.4. Tier 2, Risk Management Option for Nonresidential Structures with Basements Florence has several buildings on Main Street that are nonresidential or commercial buildings. The NFIP handles these commercial buildings very differently than residential. Provided a nonresidential structure is flood proofed to at least one foot above the base flood elevation, the flood insurance premium reduction is available. Residential structures are not eligible for that same credit for dry flood proofing.
Residential structures are not eligible for that same credit for dry flood proofing.
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Figure 6-11. Existing nonresidential building with basement flooding.
For nonresidential buildings, additional opportunities are available that are not available for residential buildings. These include the possibility of moving some utilities to second stories because of availability of space. Businesses in the commercial buildings get a flood insurance premium rated for the Dry Flood Proofing measure.
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Figure 6-12. Proposed risk management option: Dry flood proofing a nonresidential building with a basement.
6.3.5. Tier 2, Risk Management Option for Structures with Crawl Spaces In Kansas, crawl spaces and basements are common, since these are needed to offer shelter from tornados, however, crawl spaces may need flood mitigation measures to be resilient to flood damages. One way to mitigate is to wet flood proof.
Figure 6-13. A home in Florence with a crawl space.
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Figure 6-14. Existing crawl space that floods.
Figure 6-15. Proposed risk management option: Wet flood proofing a crawl space.
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6.3.6. Tier 2, Risk Management Option for Structures with Slab on Grade Foundations Property owners with slab on grade buildings can choose from several risk mitigation options. • Elevation on fill • Dry flood proofing • Wet flood proofing, elevating inside • Wet flood proofing with addition Flood insurance still required for residential buildings.
Figure 6-16. A home with a slab on grade foundation in Florence, Kansas.
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Figure 6-17. Existing condition of flooding on a slab on grade building.
Figure 6-18. Proposed risk management option: Elevating a building on fill.
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Figure 6-19. Proposed risk management option: Dry flood proofing.
Figure 6-20. Proposed risk management option: Wet flood proofing.
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Figure 6-21. Proposed risk management option: Wet flood proofing in main floor addition.
6.3.7. Tier 2, Risk Management Option, Relocation Many buildings in Florence are candidates to be relocated. Any that are in good condition, meaning the wood frames are stable and the property owners have maintained the building well, might be relocated. Large buildings can be relocated off of their foundations and moved to new sites. This includes slab on grade and masonry structures, although these cost significantly more. Florence has some sites on the west side of the city that are good candidates. Good candidates are any site where the finished floor would be at the advisory elevation is 1273.8. This is based on the analysis the Kansas Division of Water Resources found in the proposed map in spring of 2018. The north side of the city base flood elevation could be as high as 1272.78, and the state’s required freeboard is plus one foot. However, this would be only if the city was not able to certify the levee. 6.3.8. Tier 2, Risk Management Option, Buyouts Some buildings are in generally poor or fair condition. When this is the case, the building might not be worth saving. Some buyouts might offer an opportunity for the city to expand a park. Buyouts also offer an opportunity to add green infrastructure. Open space values are also a benefit. Green infrastructure offers the chance to address other issues such as water quality and rain infiltration. 6.3.9. Tier 2, Parametric Cost-Benefit Analysis of Nonstructural Risk Management Options Determining the economic feasibility of implementing any of the recommended nonstructural mitigation techniques was beyond the scope of this study. Evaluating costs and benefits for multiple sites is an intensive analysis, although technical service may be requested through multiple USACE programs,
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including the Silver Jackets proposals, the Flood Plain Management Services, the Planning Assistance to States, and the Continuing Authorities Program. The cost and benefits analyses would include the feasibility level cost estimate of each of the mitigation measures would be required, then annualized over a 50-year project life to determine the annual cost of providing flood risk management per individual building. Similarly, if the annual benefits derived from each individual mitigation measure could be determined, by estimating the reduction in future flood damages prevented, where those benefits are proportionally weighed against the probability of future flood events and the damages which could have occurred to each individual building from those future floods, a comparison of annual benefits and annual costs could be conducted. If the annual benefits for a building are divided by the annual costs for that building, a benefit to cost ratio (BCR) can be determined. A BCR greater than 1.0 indicates that the mitigation measure has more benefits than costs and is worth further consideration for implementation. Past construction projects have required a strong BCR, and the reviewers and the risk portfolio had trouble prioritizing projects with less than 2.0 BCR for features like dams, levees, and channels. However, in the past five years leading up to 2018, the USACE approval of nonstructural projects has recognized those only need a BCR of 1.0 to move to construction in the Continuing Authorities Program. The USACE-Kansas City District has done nonstructural cost-benefit analysis in Kansas, allowing parametric cost estimating, however, calculating benefits will still be needed. Prior studies in Kansas, such as the Little Apple Nonstructural Assessment for Manhattan, Kansas provide useful information to property owners in Florence, Kansas. The table below offers planning level cost estimating for a small sample of Florence properties to help give perspective to the property owners on their possible decisions to further diversify their flood risk management, beyond the Figure 6-22. Candidate property for building relocation. existing levee.
Table 6-3. Planning level cost estimating for some risk management options Measure ID# Example Cost Cost Property Estimate Estimate Address Minimum Maximum Relocation 17 234 MARION $142,200 $173,800 Buyout 12 213 W 2ND $68,400 $83,600 Elevate to BFE+1 1 101 DOYLE $90,000 $110,000 Basement fill 96 201 W 5TH ST $97,200 $118,800
Flood insurance provides the most resilience measure and helps the community to thrive in the long term. Many variables go into rating a flood policy. Some basic first questions are is the building use residential
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or nonresidential. Characteristics of the building are also important. The status of levee certification is also important, because if uncertified then the flood zone is for a higher flood risk and consequently a higher flood insurance premium for all property owners in the leveed area. The table below provides a very general overview of this to help understand. The assumption for residential is the maximum coverage limit of $250,000. The assumption for nonresidential is the maximum coverage limit of $500,000. Table 6-4. Example Cost of Annual Premiums for Flood Insurance in Florence. Residential Nonresidential Cost Cost Cost Estimate Estimate Cost Estimate Estimate Flood Zone Minimum Maximum Minimum2 Maximum4 X Zone $347 $425 $2,671 $3,265 D Zone $2,430 $2,970 $5,940 $7,260 AE Pre-FIRM $2,700 $3,300 $15,300 $18,700 AE Post FIRM @BFE $1,800 $2,200 $49,500 $60,500
If a professional engineer were to certify the levee, Florence would remain in an “X-protected by levee” zone. Flood insurance would not be required of lenders, because the certification proves that the town has a ‘reasonable protection’ from flooding. Florence, Kansas would no longer be in the 1% annual chance exceedance or special flood hazard area. Special Flood Hazard Area, as defined by FEMA: The land area covered by the floodwaters of the base flood is the Special Flood Hazard Area (SFHA) on NFIP maps. The SFHA is the area where the National Flood Insurance Program's (NFIP's) floodplain management regulations must be enforced and the area where the mandatory purchase of flood insurance applies. The SFHA includes Zones A, AO, AH, A1-30, AE, A99, AR, AR/A1-30, AR/AE, AR/AO, AR/AH, AR/A, VO, V1-30, VE, and V. Currently, no policies are in force in Florence at all, and this means more awareness about the lower cost available for premiums should be made clear and awareness on diversifying the property owners’ approach to the flood risk is, as well. Though property owners would not be required to carry flood insurance, a Preferred Risk Policy is recommended to property owners. Even though Florence could be mapped to show a minimal flood risk, no guarantee exists that flooding will or will not happen. The Rating section of the 2018 Flood Insurance Manual would be a good place to start determining dollar-figure estimates for specific types of buildings. The direct web link is below. Remember that the rating for the policy will be dependent on the status of the levee certification. https://www.fema.gov/media-library-data/1523307287100- 4cf9726b2eb04c3471a3e9d37a58fa6a/05_rating_508_apr2018.pdf A next step for property owners might be to have the city and county request USACE assist in calculating more properties and the benefits from reduced flood damage costs.
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6.4. Flood Risk Management Options for Critical Facilities and Public Property
Critical facilities should be resilient to both the Primary and Secondary Scenario. Resilient communities make critical infrastructure less susceptible to the 0.2% annual chance Damage to critical exceedance, and sometimes much less frequent, more severe facilities could be the events. Damage to critical facilities could be the difference between difference between having a community that thrives versus one that is setback years having a community economically. that thrives versus The city may consider several buildings as critical infrastructure. In Florence, the Secondary Scenario is at elevation 1277.50. In the one that is setback event of a levee overtopping, as described in the Secondary years economically. Scenario, several key city facilities will be impacted: • Water treatment facility • City buildings
o Fire station o Emergency medical responders o Police o Emergency operations center When funding allows, the city facilities should be relocated to high ground west of Doyle Street. The water treatment facility on the north side of the city, located in the leveed area, is susceptible to the 0.2% annual chance exceedance. For long term resilience, a plan should be developed to relocate this to slightly higher ground to the west.
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Table 6-5. List of Land Survey Point Numbers for Critical Facilities and Public Property.
Land Survey Point Number Description
3 railroad depot
20 U.S. post office
44 public library
45 fire department
48 main park
110 city offices / emergency responders / ambulance
132 Unity Park
133 old school
201 public housing
214 public housing
227 water treatment station
Some of these locations are probably not critical facilities. While parks, libraries, and others are described, the project team relies on the city to confirm that these are not in fact critical facilities. Some maybe staging areas for flood fighting, and others maybe rallying points or refuge locations. If this is so, the possibility of flooding and depths of flooding, should be considered as factors to adapt the city’s overall emergency preparedness planning.
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Several city facilities would be affected significantly for the Secondary Scenario. Many of these should be relocated to the west side of the city limits and higher than the 0.2% ACE elevation 1277.50. This is more specifically defined by the 1278 contour line, which is visible in the map in this section. Any relocations should be on higher ground west of the ends of the cul-de-sacs located west of Doyle Street. The city offices have a finished floor elevation 1270.06, and a six-foot tall individual would be swimming. Possible redevelopment efforts might relocate these city facilities to where the old high school was.
Figure 6-23. Topographic map for Florence, Kansas. The water treatment facility is an important critical facility. This facility filters water and then the water is pumped to the water tower. This building is high and dry for the 1% annual chance exceedance in the Primary Scenario, however for the Secondary Scenario, the building is susceptible to the 0.2% annual chance exceedance (ACE), where the water surface is expected to exceed the finished floor elevation 1274.74. To improve the resiliency of the city, the city should consider this critical structure be dry flood proofed up to the 1277.5 elevation. This would be just under three feet high, which is within the structural limit for dry flood proofing. Flood proofing to that level may prevent expensive damage and substantial delays in flood recovery. Some of these public buildings are not critical infrastructure, but they have a very meaningful cultural resource value to the community. The railroad depot is being planned for a preservation project. The Primary Scenario may be enough for the railroad depot, although the risk of severe flooding from the 0.2% ACE might be an important consideration for any rare cultural items that may be located to the site in the future.
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7.0. Suggested Risk Management Options for Floodplain Managers and Emergency Managers In addition to the flood risk adaptive measures recommended in the previous section, this section presents other measures, which should be considered for minimizing future flood damages.
7.1. Emergency Action Plan
The current emergency action plan helps. The EAP should consider the timing to take specific actions, when flooding is severe. If the levee overtops, the timing to inundate the main city offices would be a matter of hours. Messages should be developed for specific parts of the leveed area, and if the city could designate a handful of numbered zones, the messages could be specific to those areas. Various flood impacts for the gage, called Cottonwood River Near Florence, should be cited in the EAP and used for thresholds tied to specific actions. At the least, the closure of the two closure Figure 7-1. Flood categories on the gage, structures on the levee ought to be done. Two Cottonwood River Near Florence. members of the city staff should enroll for alerts from this gage and have settings for phone alerts at several stage levels. Flood Impacts, Cottonwood River Near Florence:
48 The southern section of the levee system around the city of Florence may become breeched. If levee is overtopped, flood waters may rise up to four feet deep across most of the city streets of Florence. Expect dozens of homes to be flooded.
32 Water levels can reach nearly 10 inches above ground floors of houses less than 1 mile north of gage site that is 2.5 miles east of Florence.
27 Flooding is sufficiently extensive to reach driveways of property within 1.0 mile of the gage site. Expect extensive cropland and field flooding.
24 Outside the levee system in southeast Florence, flood waters flow across Park Ave Road and reach the foundation of a residential home.
22 Minor flooding of the left bank and roads along the north bank will begin.
7.2. Risk Communication
Community outreach initiatives such as providing flood information flyers, erecting high water mark and flood history signs, can increase the awareness of flood risk among residents, which can lead to better response time in the event of a flood. Results from this assessment may be used by local and county officials to conduct emergency preparedness activities such as evaluating roles and responsibilities, flood fight plans, and response capabilities in the event of a flood. Engaging the public with these suggestions below could have a significant impact on improving the understanding and the usefulness of the previous measures that have been discussed in this report.
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7.2.1. Historic Flood Signage The city has a good web page with information on past flooding and an old photograph that communicates the past flood levels very well. Even though that old photo is prior to the levee construction, the photo would be a very good reminder to the public of the residual risk of the levee flooding in the future. The Silver Jackets Program, at the time of this report, is offering assistance making these signs through 2018. One example is shared in the figure in this section. The signs help remind the community of the flood risk and may help nudge property owners to look at how to diversify their approach to mitigating potential flood damages. Figure 7-2. A historic flood sign used to communicate the
flood risk of high water in nearby Marion, Kansas (2018). 7.2.2. Annual Outreach To Property Owners in the Leveed Area An annual outreach project would be very easy to prepare, given all of the data already assembled in this report. This type of outreach service is creditable for this community, which participates in the FEMA Community Rating System (CRS). The Activity 620 requests that such a project achieve the following: • Tell people about their flood risk • Explain how they would be warned of a levee failure • Provide evacuation routes and meeting points • Describe benefits of purchasing flood insurance An annual outreach project is one of eight specific items that are creditable. The example shown in this section is modeled in a template provided in the appendix. The template can be adapted for Florence, and the city may place the required information on the city’s web page. In addition, the state may provide a web page that could support levee sponsors and their stakeholders to better address Figure 7-3. Example annual their risk management options. mailer for California communities (2017).
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7.3. Development Areas
Additional opportunities for reducing the flood risk may include relocation of existing buildings or businesses to redevelopment sites as identified on higher ground west of Doyle Street. These sites are still within or reasonably close to the central business district, but on parcel which would have a lower flood risk. Areas outside the leveed area are at risk of both inundation and higher velocities associated with the floodway. Bridges and roads may overtop in those areas. In addition or instead of nonstructural mitigation, future flood risk reduction considerations for those roads and bridges could be to improve conveyance through bridges. Local zoning and/or building codes may be used to reduce flood risk for new construction and for community flood risk management required by the National Flood Insurance Program (NFIP). Given the greater flood risk identified between the data developed for this assessment and the effective FIRM, the project team highly recommends that the community coordinate with the Kansas Department of Agriculture, Division of Water Resources, on potential ordinances that could be adopted by the community for increasing flood risk management.
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8.0. Combination Structural and Nonstructural Measures In some situations, the most effective way to reduce a community’s flood risk is to consider a combination of nonstructural and structural features within a project area. Florence has a good example of combined structural and nonstructural measure, currently, related to the levee. The levee relies on two drain pipes for interior drainage, and the figure in this section shows these. The city has open space on the west and upstream sides of the levee, and that allows for ponding. Keeping these areas as open space and not allowing development on that land demonstrates how structural and nonstructural measures can be combined. The levee is the structural measure, and the land regulation
Figure 8-1. Levee interior drainage will pond at two locations (light blue shading) showing the limits for the 1% annual chance exceedance.
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keeping the area as open space is a nonstructural measure. The city and general public should maintain this practice of wise use of the floodplains, keep these zoned as open space, and only allow uses such as ball fields or recreation. USACE recently provided a resource for combining structural and nonstructural features for levee sponsors in the USACE levee program, but also for floodplain leaders across the United States. This new resource, The Sponsor’s Guide To the USACE Levee Safety Program (EP 1105-1-1, June 2018), is very helpful in achieving the goal of mitigating flood risks.
Figure 8-2. Risk management options may be combined to address factors driving the risk (The Sponsor’s Guide To the USACE Levee Safety Program). The graphic above helps communities see the full menu of flood risk management measures that might be combined. A diverse set of measures should be part of the community’s flood risk management playbook. Each community will have a variety of reasons that affect why the select their preferred measures. Each levee owner selects a unique set of risk management options that may work in their community. The only wrong decision in this regard is expecting one measure will provide the most resilience to flood hazards.
A diverse set of measures should be part of the community’s flood risk management playbook.
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9.0. Conclusion and Next Steps Florence, Kansas, a community located behind a levee, will always have a residual risk of flooding. Flood risk management is a team sport. While the governments at the federal and state level have programs to help manage flood risks, the rest of the team is local. The city and the individual property owners become familiar with their roles and responsibilities to reduce flood risks. This is especially true with flood insurance with the role of the property owners. Flood insurance is one of the best ways to reduce risk. After a flood, those with policies can be fully restored for properties similar to those in Florence. Flood insurance is a way to spread out …property the risk through a national program. Flood insurance is not part of home owner insurance. But, property owners alone can take the owners alone can next step to get flood insurance coverage. take the next step Property owners can take action to lower their risk. After reading to get flood this report, property owners better understand the flood risk. Besides flood insurance, many of the other possible risk insurance management options would not cost too much to take action. coverage. The project team recommends several risk management options. The property owners should take advantage of the how flood insurance helps. Emergency managers need to update the emergency action plan, as the flood hazard section has serious deficiencies. Flood warning is another important element that is recommended, and the NOAA National Weather Service’s web page, water.weather.gov, will be very useful to issue evacuations for future flood disasters.
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At the property level, the study recommends the property owners look closely and consider the nonstructural measures, and a count to summarize these is presented in the table below. Elevation on fill is a more costly means to elevate, but this measure has been used in nearby communities, such as on Wildcat Creek in Manhattan, Kansas. The property owner will have to decide on whether elevation on fill is preferred to the other means, therefore, this is listed as zero. This is a good example emphasizing the role of individual property owners.
Table 9-1. A summary counting the nonstructural measures recommended as risk management options for buildings in Florence. Measure Number of Feasible Buildings
No action 29
Wet flood proofing 199
Flood openings 115
Fill basement 13
Dry flood proofing 9
Elevation on foundation walls 132
Elevation on piers 13
Elevation on fill 0
Relocation 44
Buyout / acquisition 43
Anchoring 14
The project team helped identify potential nonstructural measures on a building by building basis which could be implemented for reducing future damages due to flooding. This assessment considered 264 buildings located within the special flood hazard area to determine whether or not nonstructural flood risk adaptive measures would be practical for implementation on a larger scale throughout the community. As a function of the assessment, the characteristics of flooding, such as depth, velocity, and areal extent were combined with building attributes for each of the 264 buildings to determine the flood risk for the target 1% annual chance exceedance flood event. From this information, potential nonstructural measures for each building could be determined. The measures proposed were scaled to the flood risk for each building. As an example, if the 1% annual chance exceedance flood depth were no greater than a foot or two above the first floor elevation of a building, there would be no need to consider acquisition or relocation of the building, when dry flood proofing the building may significantly decrease the flood risk. Since flooding within the city could occur at any given time prior to the community as a whole, or owners/tenants individually, implementing permanent measures, this assessment also provides practical information for the implementation of temporary measures. Materials and equipment needs are described
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in order to provide the owner/tenant with enough background information to develop a successful emergency flood response plan. While dry flood proofing of individual or small groupings of buildings appears to be practicable for eliminating or substantially reducing flood risk, it was noted that many of the nonresidential buildings contain crawlspaces of varying depth (typically between 2- to 4- feet), which could affect the performance of the dry flood proofing if floodwaters are allowed to infiltrate exterior siding, foundations, and surrounding soils to damage the structure from the interior. For these situations, the crawlspace as well as the exterior of the building must be modified in order to successfully prevent floodwaters from entering each individual building. Appendix B contains the recommendations for a sample building, typical of those located in the Florence, which illustrates the structure modifications and material requirements for reducing the existing flood risk through dry flood proofing. Knowing the community level cost for the nonstructural measures for all of the buildings counted in the table above is helpful in gaining perspective. The project team calculated cost estimates using single building values in Table 6-3 in the table below. Table 9-2. Community level cost estimate for implementing all the nonstructural measures for the buildings. Measure Number of Community Level Cost Feasible Effect Structures No action 29 $0 Fill basement 13 $1,544,000 Elevation to BFE+1 132 $13,200,000 Relocation 44 $6,952,000 Buyout / acquisition 43 $3,268,000 Based on the costs to physically implement the nonstructural measures as shown in the table above, the community should have a better understanding of the value of flood insurance. Realistically, to implement the measures above would only be possible if grant assistance were available. However, some property owners could conceivably elect to add this to their approach of managing their flood risk. Compared to a commonly accepted value for levee certification, roughly $250,000 nationwide, the tradeoff is a jump of about $396,000 in annual flood insurance premiums going from Flood Zone X to AE (a certified levee) from $91,000 for Zone X (for 264 properties using flood insurance premiums in Table 6-4). One of the important steps in flood risk management is having the public involved in the decision process. Those that flood are stakeholders in both understanding the risk and understanding the possible options to manage the risk. The Silver Jackets Program is available and can provide technical services for any public meeting. Many of the figures in this report can be produced on posters or with projectors to engage the public in the process of deciding the best flood risk management options for the community and for their own property. This report provides a detailed perspectives into various possible measures. The community can build on this to develop a more specific floodplain management playbook. If so, that activity is creditable under Activity 510 of the FEMA Community Rating System. That action alone can raise the community to a better level in the CRS and continue lowering the flood insurance premiums. All these measures will help make Florence more resilient to flood risks.
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Appendix A: Flood Risk Management Glossary This is a glossary for leaders of flood risk management to use with the public for managing the Nation’s flood risks. Bold words are defined and used to link to other definitions. Actions are specific efforts to implement any Measure(s) intended to mitigate flood hazards and that help a community achieve goals and objectives. Activity is one of two terms associated with being a Measure. An activity could be one-time, periodic, or continuing. Local, state, and federal agencies may do many activities to manage the use of resource(s) to address Goals tied to Risk Management. Acquisition, or Buyout is a physical means of managing flood risks by addressing consequences in the floodplain with the purchase and elimination of flood damageable buildings, allowing for inhabitants to relocate to locations away from flood hazards. Alluvial Fan is a large area of soil, rock, and debris spread out by floodwaters into a cone shape at the base of narrow canyons on a flat plain and creating uneven land at the foot of a mountain range. Alluvial Fan Flooding is dangerous flash flooding occurring on the surface of an Alluvial Fan that may quickly change flow paths and may also have a fast moving Debris Flow. Arroyo is term for dry river beds and creeks in deserts or dry areas of the U.S. that can be dangerous during a Flash Flood because the unexpected rainfall runoff may occur very far away from the area flooding. Base Flood is the flood for a specific location on a stream or river that has a 1-percent probability of being equaled or exceeded in any given year. The flood is wrongly referred to as the 100-year flood, which misleads the public to believe that 100 years pass between such floods. Base flood is a Land Use Regulation definition tied to the federal program for Flood Insurance. Base Flood Elevation is a Land Use Regulation term, which is defined for the federal program for Flood Insurance. The elevation is the height calculated using historic rainfall for the 1- percent chance in a given year and in feet above sea level. The term is not a safety standard. Basin, or Watershed, is all the area that drains rainfall from places higher, or upstream, of a point on land or along a stream or river. Berm (also landform) is a Feature made of soil that act as a barrier along a watercourse to exclude floodwaters from a very limited range of minor flood events from a small portion of the floodplain, usually for one building. Beneficial Use of floodplains is a useful way to go beyond managing flood risks, encourage a more diverse natural environment, and add recreational amenities in what is regarded as a wise use of floodplains. Communities also find this adds value in terms of social benefits, which help the community thrive.
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Building Codes are a part of Land Use Regulation and are for communities to control building design and construction materials, including anchoring, materials resilient to wet conditions, and structural strengths to address water pressure and velocities of waves. They may also place requirements on electrical wiring, mechanical equipment, and often may address sanitary sewer backup. Bridge Raises are a form of a bridge enhancement and are vertical improvements to improve the area of flow, similar to Bridge Widening, although a raise will also require elevating the profile of the road and involve more costs. Bridge Widening is a form of a bridge enhancement that provides more area for floodwaters to drain by increasing the distance between the ends of the bridge and then tying to a wider channel. Bridge widenings may be replacing a structure or culvert that allows a road to cross a stream. Buyout, or Acquisition is a physical Nonstructural Measure and involves purchase and elimination of flood damageable buildings, allowing for inhabitants to relocate to locations away from flood hazards. Bypass, or Diversion, is a Feature that is an additional or new channel to a creek or river and may be used to reduce the amount of floodwaters in the area of concern. Capacity Exceedance is when a feature, such as a Levee, Dam, Channel, or elevated building, has floodwater overflow the top of the structure, overflow above a channel bank, or rise above the level of an elevated building. Channel is a Feature that uses slope and gravity to drain floodwaters. Channel Alteration is a Feature and a change communities may make to Channel. Changes made include those to the stream banks and stream bottoms, including side slopes, straightening the path in a new channel, widening, and deepening. Combinations of these are common, and Bridge Widenings are frequently necessary as well. Climate is defined by the meteorological elements, including temperature, precipitation, and wind, which characterizes the general conditions of the atmosphere over a period of time (typically 30 years) for a particular region. Coastal refers to the coastlines and bays of the tidal waters of the United States or the shorelines of the Great Lakes. This term is used to define a source of flooding, where the other term is Riverine. Community a city, village, town, county, township, parish, borough, Indian tribe or authorized tribal organization, Alaska Native village or authorized native organization, or other local government with the statutory authority to enact Land Regulations. Comprehensive Plan or “Comp Plan,” refers to a document, not limited to flood risk management, covering the entire geographic area of a community and expressing community goals and objectives. The plan lays out the vision, policies, and strategies for the future of the community, including all of the physical elements that will determine the community’s future Development. This plan can discuss the community’s desired physical Development, desired rate and quantity of growth, community character, transportation services, location of growth, and siting of public facilities and transportation. In most states, the comprehensive plan has no authority in and of itself, but serves as a guide for community decision-making. Current and future condition flood mapping will enhance any comprehensive plan. A
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Floodplain Management Plan or risk management plan for flood hazards should build on the vision of a Comp Plan. Consequence is the effect, result, or outcome of flooding reflected in the potential loss of live, economic losses, and adverse environmental impacts. Consequence is a part of defining Flood Risk. Critical Facility is a building or a structure that, if destroyed, damaged, or if function is lost, will badly affect a community. Critical facilities are 1) vital to flood response activities or crucial to the health and safety of the public before, during, and after a flood, such as a hospital, emergency operations center, electric substation, police station, fire station, nursing home, school, vehicle and equipment storage facility, or shelter; and 2) are facilities that, if flooded, would make the flood problem and flood impacts much worse, such as a hazardous materials facility, power generation facility, water utility, wastewater treatment plant, or transportation system. Culverts, sometimes referred to as Bridge Culverts, are assemblies of pipes, which could be metal or concrete, or assemblies of rectangular box segments, often concrete, which allow creeks to cross below roads. Culverts may be considered to be bridges by some, although culverts have more difficulty passing floodwaters on the upstream end than bridges. Dam is a Feature made of soil that allow the long-term storage of large amounts of rainfall runoff to reduce the flood flows impacting those downstream. Dams often have multiple purposes tied to them, including recreation, water supply, and environmental purposes. Detention Basin is a Feature made of soil that allow usually short-term storage and treatment of rainfall runoff to reduce the flood flows impacting those downstream. Detention basins are sometimes dry during wet weather, and they may support recreation activities. Debris refers to trash, junk, litter, discarded remains of something destroyed, landscape waste, or vegetation that may reduce the ability (of one or both) 1) to drain a pipe or channel; 2) to store floodwater behind a Detention Basin or Dam. Debris Flow is a dangerous type of flooding from hills or mountains that is made up typically of mud, rock, and vegetation. These are often tied to channels draining from areas that experienced wild fires, which burned off the trees and brush that kept the soil in place. Depth Grids are an information and education measure that uses web viewers to show inundation maps illustrating the depth of flooding, usually with varying color. Development is any manmade change to improved or unimproved real estate including, but not limited to, buildings or other structures, mining, dredging, filling, grading, paving, excavation, drilling operations, or storage of equipment or materials. Diversion, or Bypass, are Features that are an additional or new channel to a creek or river and are used to reduce the amount of floodwaters in the area of concern. Dry Flood Proofing is a physical Nonstructural Measure for Flood Proofing buildings in the floodplain and involves sealing walls with waterproofing compounds, impermeable sheeting, or other materials to prevent the entry of floodwaters into damageable buildings. Dry flood proofing is applicable in areas of shallow, low velocity flooding.
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Educational Opportunities include the chance to help the public learn of the natural and beneficial values of floodplains and low impact Development upstream. Elected Officials are selected through democratic processes to be mayors, city council members, levee board members, drainage district directors, and similar positions charged with leading and making decisions that benefit the public. Elevation is a physical Nonstructural Measure and involves lifting the building in place so that the building sees a reduction in frequency and/or depth of flooding during high-water events. Elevating buildings can be done with earthen fill, foundation walls, piers, piles, posts or columns. Selection of the proper elevation method depends on flood characteristics such as flood depth or velocity. The additional cost of additional height for the raising of the building is usually minimal compared to the first foot, due to start-up costs for the builder, so frequently property owners add Freeboard. Elevation Certificates are an information and education measure and are official documents provided by professional land surveyors to determine if a building is affected by floodwaters and is used to determine flood insurance premiums. Emergency Preparedness Plans, or Emergency Action Plans, are a measure established by local officials that identifies hazards, risks and vulnerabilities. The plan should include the community’s response to flooding, but the plans should establish the roles and responsibilities related to the following items well in advance: 1) activation of floodfighting measures (closure structures, sandbagging, pumps, etc.), 2) location of evacuation centers, 3) evacuation routes, and 4) flood emergency processes (including public messaging, how to direct volunteers, etc.). Emergency Action Plans are considered a nonphysical Nonstructural Measure under the full menu of flood risk management measures. Emergency Relief includes funding and or staff from a government entity that is available for flood disasters. Typically, federal and state government programs are established to provide relief, although communities also may have mutual aid agreements. Many not-for-profit organizations exist and also provide emergency relief. Erosion Protections are measures that help when fast moving floodwaters cause loss of land, including stream bank failures. Heavy rock and naturally occurring roots can provide erosion protection. Evacuation Plans are a public resource with directions and places to go and are for the public to understand prior to severe flooding. Evacuation plans are normally part of Emergency Preparedness Plans. The foresight should have included action thresholds for leaders to begin flood response, contact methods to effected people, and predetermined messages for risk communication. Effective plans use flood maps and understand the rate of rise of floodwaters for various flood severities. When used in conjunction with flood warning systems, evacuation plans can provide significant loss of life avoidance and flood damage reduction benefits. Evacuation planning should consider vertical evacuation as well as the traditional horizontal evacuation. Rally points as well as evacuation routes should be thoughtfully planned and communicated
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to the public. Evacuation plans are considered a nonphysical Nonstructural Measure. Evaluate is a planning process that a community’s Risk professionals do when reviewing Measures. Resilient communities have included the public and evaluated the full menu of measures to prioritize Actions, then used that evaluation in a playbook for Elected Officials to Mitigate flood hazards over the long-term to help communities thrive. Exposure is the potential for people and assets to come into direct contact with floodwater as a result of their location in a floodplain. Feature is one of two terms associated with being a Measure. A feature is something that may be constructed. Local, state, and federal agencies may build various features to address Goals tied to Risk Management. Fill Basement is a Flood Proofing measure to eliminate flood risks for some buildings. This normally requires breaking up the concrete floor slab to allow water pressure to equalize. Often this measure is done with a first story addition. Flash Flood is a flood occurring with little or no warning and has water levels that rise very quickly. Flood is a term for the temporary condition of partial or complete inundation of normally dry land resulting from the overflow of inland or tidal waters or from rainfall runoff. Flood Elevations are an information and education measure to begin the decision making process with Stakeholders in choosing the best measure to address their flood risk, based on their needs and finances. property owners Flood Insurance is a mechanism for spreading the cost of losses both over time and over a relatively large number of similarly exposed risks. The funds assist in recovery from a flood event and are provided by the federal government through a subsidized national program, although the rates will increase as the government plans to end subsidies. Flood insurance is considered a nonphysical Nonstructural Measure. Flood Hazard is a danger or condition that causes harm to people or property damage in a floodplain. Natural hazards include flood, wind, and earthquake, although a flood loss results from humans making unwise choices in floodplains. Floodplain is the lowland and relatively flat areas adjoining inland and coastal waters including flood prone areas of offshore islands; and including, at a minimum, that area subject to a 1-percent chance of flooding in any given year. Floodplain Management is a continuing process, involving both federal and nonfederal actions that seek a balance between use and environmental quality in the management of the inland and coastal floodplains as parts of the larger human communities. The flood damage reduction aspects of floodplain management involve modifying floodwaters and modifying the susceptibility of property to flood damages. The former embraces the physical measures, or Features, often wrongly referred to as "flood control;" the latter includes regulatory and other measures intended to reduce damages by means other than modifying floodwaters. By guiding floodplain land use and Development, floodplain regulations, or Land Use Regulation, seek to reduce future susceptibility to flood hazards and damages consistent with the risk involved and serve in many cases to preserve and protect natural floodplain values.
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Flood Proofing (also floodproofing) is any combination of Structural Measure or Nonstructural Measure changes or adjustments incorporated in the design, construction, or alteration of individual buildings or properties that will reduce flood damages. Flood proofing is considered a physical Nonstructural Measure and may be considered Dry Flood Proofing or Wet Flood Proofing. Flood Risk, or Risk, is the uncertain possibility of flooding causing bad outcomes, so this includes the Probability and Consequence of the flood impacting humans. Flood Risk Management is the mix of federal and nonfederal government policies and programs that influence the decisions made by communities and individuals relating to floodplain location and use and their choice of actions to reduce flood risk and manage residual risk. The term also encompasses the decisions made by all levels of government and by individuals to implement actions to reduce flood hazard, exposure, and vulnerability and to increase resiliency. Flood Risk Reduction Actions are mitigation efforts, or Actions, taken in advance of a flood that are intended reduce the likelihood of a future flood or the potential adverse consequences. They include actions to reduce the flood hazard, reduce exposure, and reduce vulnerability. Flood Walls are Features commonly made of concrete that act as a barrier along a watercourse to exclude floodwaters from a limited range of flood events from a portion of the floodplain. Flood Warning Systems are a technical means of applying sensors and using notification devices to give the public advanced notice of flood conditions in order to allow actions such as evacuation, flood fighting, and relocation or elevation of property prior to flooding. Flood warning systems are considered a nonphysical Nonstructural Measure. In many locations across the Nation, advance forecasts are available for major river systems, although for other areas flood warning systems can be used on small creeks as well, if they community, property owner, or drainage district finds the cost feasible. Flood warning systems may include rain gages and stream gages to help predict flooding and may be able to tell when to expect high water. Flood Mapping is often tied to these systems to improve public understanding and to do Risk Communication. Floodplain is a land area with any chance of having a flood. Floodplain Leaders are those authorized by a community’s elected officials to be champions of both Floodplain Management as well as sustained Flood Risk Management work. Floodplain Management are the policies and programs of federal and nonfederal government directed to actions taken in advance of a flood that are intended to limit the exposure and vulnerability of people and assets to flooding. Floodplain Management Plan is a playbook for managing the risk of flooding. This includes the story of identifying and assessing flood risk, then reviewing the full menu of Measures and explaining why each measure is or is not a fit for the community. The playbook includes prioritized actions for taking on the long-term process of doing Activities and constructing Features that manage flood risks and can be used by elected officials to justify each actions behind every measure.
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Floodplain Mapping is an information and education measure in the form of a map which shows ranges of flooding surrounding a creek, river, or lake, and this measure is a significant tool needed to begin addressing flood risk and evaluation of other measures. Various ranges of flood severity may be shown, so that the public can understand the Uncertainty of the each flood boundary. Floodplain maps may be referred to as inundation maps or flood insurance rate maps (FIRMs). Floodplain mapping is considered a nonphysical Nonstructural Measure. Freeboard is a margin of safety added to the Base Flood Elevation to account for waves, debris, miscalculations, lack of data, or changes in climate. This is a term used under Land Use Regulation and Building Codes as a protective standard for buildings, requiring additional height above the Base Flood Elevation used in Flood Insurance. The additional height helps to address Uncertainty in the severity of flooding and is included in designs for physical measures, such as Levees and the Elevation of buildings. Freeboard is one of the most common higher regulatory standard states and communities adopt. Goals are general guidelines, developed with public input, that explain what the Stakeholders want to achieve. They are usually broad policy-type statements, long term in nature, and represent the vision of the community. Objectives may accompany goals and provide a more specific intent of a goal. High-Hazard Dam is a dam that is assigned the high-hazard-potential classification for the ones whose failure or mismanagement will probably cause loss of human life. Land Use Regulation is city or county codes or Ordinances that guide Development and manage flood risks. The regulations are equitably applied local policies, sometimes at the city or county level, but also at the state level. Regulations at the local level include Ordinances, Building Codes, and Zoning. Setback Ordinances, Freeboard ordinances, Sanitary Codes, and housing or Subdivision Regulations are also examples. Funding laws may also be considered a form of regulation and serve to support flood risk management, including mill levies that might fund a drainage district’s functionality, stormwater utilities that serve to support capital improvement projects, and even sales taxes on particular Development. Local design manuals are tied to policies and may be considered an extension of flood risk management regulations, such as stormwater detention basin volumes and release rates used by local planners in the process of reviewing Development plans. Communities also may have comprehensive plans or watershed planning documents that tie to regulations. A floodplain Ordinance is the most common regulation, which is required for Flood Insurance. Land Use Regulation is considered a nonphysical Nonstructural Measure. Levees are Features made of soil that act as a barrier along a watercourse to exclude floodwaters from a limited range of flood events from a portion of the floodplain. Local Officials is a term that includes politically appointed positions, such as Chief Resilience Officer, Public Works Director, Floodplain Administrator, Hazard Mitigation Officer, or Chief of Emergency Management. The term can include Elected Officials mayors, city council members, levee board members, drainage district directors, and similar positions charged with leading and making decisions that benefit the public.
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Low Impact Development includes various Measures that promote treating rain where it falls, which is likely the most cost effective way to manage flood risks. These Measures include pervious pavement, rain gardens, rain barrels, and conserving forest canopy. The Activity of incentivizing these use of these measures on a watershed scale is one way to help address the more intense rainfall associated with climate change. Measure (also Management Measure, Mitigation Measure) is a term that refers to either a Feature or an Activity for managing Risks. Measures are combined by flood risk managers to form alternatives and programs for a site or a large geographic area, such as a community. The full menu of measures should be considered in a community’s flood risk management program or Floodplain Management Plan. Mitigate means to lessen the Risks. Mitigation Plan is a plan that documents the process used for a systematic evaluation of the nature and extent of vulnerability to the effects of natural hazards typically present in a state or community. The plan includes a description of actions to minimize future vulnerability to hazards. Floodplain Management Plans or risk management plans addressing floods may complement any all hazard mitigation plan and are a means of taking action on the number one hazard that the Nation faces: Flooding. Nonstructural Measures are permanent or contingent measures applied to a building and/or its contents that prevent or provide resistance to damage from flooding. Nonstructural measures differ from Structural Measures in that they focus on reducing the consequences of flooding instead of focusing on reducing the probability of flooding. Nonstructural measures may be physical or nonphysical. Physical include Elevation, Relocation, Buyout / Acquisition, Flood Barriers, Dry Flood Proofing, and Wet Flood Proofing. Nonphysical include Flood Warning Systems, Flood Insurance, Floodplain Mapping, Flood Emergency Preparedness Plans, Land Use Regulations, Zoning, Evacuation Plans, and Risk Communication. Ordinance is a term for a law or Land Use Regulation adopted by local government. Ponding is a flooding condition in low-lying areas caused when runoff drains to a location that traps the ponded water, which usually remains until the area dries, the ground seeps the water, or pumps take out the water. Post-flood Recovery Processes include flood damage assessments and loss cost estimating, restoring vital services and critical facilities, conducting clean up at salvageable buildings, removing debris, prioritizing repairs, connecting restoration work with funding (governmental and or not-for-profits), and providing social services for people suffering emotional stress from the flood disaster. Preserving Cultural Resources is an Activity that recognizes compatibility between historic buildings and tribal heritage and the natural environment and may require Features such as elevation or relocation, although many sites’ cultural significance is adversely affected, when these measures or flood proofing are used on the site or the building. All preservation efforts for flood risk management on these cultural resources should be coordinated early in the planning phase with the tribal leaders and the state historic preservation officer. Preserve is to prevent adverse modification to the existing floodplain environment or to maintain it. Preserving the Natural Environment is a tool that recognizes Activities and Features that treat rain where it falls, encourage storage and ground water infiltration, or keep erosive resistance, thus preventing the consequential increase in floodwaters as a result. Probability is a statistical measure of the likelihood, or the chance, that a hazard event will occur and is part of defining Flood Risk.
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Process of Relocation, a term tied to Relocation of buildings, is a series of steps to assess buildings, group them per community cohesion, and establish resources for and fund the relocations in a fair and feasible way for the community. Pump Stations are housed pumps. Pumps are mechanical devices that move water. Pump Stations are used to help drain rain from leveed areas or low areas. Public Engagement or Involvement is the process of including Stakeholders in the evaluation of the full menu of measures and by doing so helping build support for necessary actions in a community’s flood risk management planning (see also Floodplain Management Plan). Floodplain leaders achieve a more resilient state for the community by engaging the public in decisions about measures. Recreational Enhancements are Features like hike and bike trails that are compatible with flood risk management features, while contributing to public wellness by integrating infrastructure with the natural environment. Re-Development Policies allow communities to reconsider use of lands and functionality of utilities and services to return that land to open space for floodwaters, including pre-identifying high risk areas, enabling a funding stream in advance, and engaging easement or other real estate mechanisms to permanently evacuate the area. Relocation is a physical Nonstructural Measure and involves moving the building to another location away from flood hazards. Relocation is the most dependable method of protection and provides the benefit of use of the evacuated floodplain. Residual Risk is the level of flood risk realized by people and assets in a floodplain that remains after implementation of flood risk management measures and the actions to apply those measures. Residual risk includes the consequence of capacity exceedance as well. Because even large Features, like dams or levees, always have a residual risk, floodplain leaders consider a diversity of measures to reduce the community’s flood risk. Residual Risk Management Actions are actions that increase the ability of people and property to return to preflood conditions in the aftermath of realizing flood damage. Resiliency (also Resilient) is the ability of communities to return to preflood conditions in the aftermath having flood damages. Restore is to reestablish a setting or environment in which the natural functions of the floodplain can again operate. Restoring the Natural Environment is a tool that recognizes Activities and Features that recreate natural beneficial functions lost due to land Development. Risk, or Flood Risk, is the uncertain possibility of flooding causing bad outcomes, so this includes the Probability and Consequence of the flood impacting humans. Risk Analysis is an approach to evaluation and decision making that explicitly, and to the extent practical, analytically, incorporates considerations of risk and uncertainty in a flood damage reduction study. Risk Assessment is a process of defining the nature of the risk, the chance (Probability) and the Consequences, either described with numbers or simply generally described. Risk Communication is an exchange of information to allow better understanding of risk. Risk communication is considered an information and education measure, or more specifically an Activity, to
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help the public understand risks, involving a variety of information tools such as presentations, workshops, hand-outs, mailers, and pamphlets to communicate flood risk and all possible measures available to communities that can reduce the flood losses. Risk communication is considered a nonphysical Nonstructural Measure. Risk Management is about taking actions to accept, assume, and manage risk. Riverine is a term applied to inland areas of water produced by a river or stream. Riverine floodplains have readily identifiable channels. This term is used to define a source of flooding, where the other term is Coastal. Road Closings is the Activity for managing risk of loss of life at locations where water bodies flood enough to affect traffic and when enough time or forecasting is provided to place signs in advance to close a road. Six inches of water is deep enough to float a car. Sanitary Codes regulate, a part of Land Use Regulation, disposal of water but may also allow a community to regulate septic tanks and other wastewater structures to function properly and prevent contamination in the vicinity of flood hazards. Sediment Controls are Activities and Features that improve water quality but may also reduce runoff. These Features keep soil in place, including vegetation, grading of the ground, or using synthetic materials. Trees and brush for saturated soil on steep slopes are important in preventing landslides and debris flows. Construction sites typically have synthetic Features until vegetation matures. Setback Ordinance is a Land Use Regulation adopted by local government that wants to set aside land adjacent to a stream or river and manage Development to prevent flood losses. Typically, the stream corridor is preserved within a specific distance of the centerline or top of the stream bank on either side. Stakeholder is one individual, or a group, including businesses, private organizations, and citizens that will be affected or believe they may be affected in any way by Measure, an Action, or a Land Regulation. Stage. The vertical distance in feet above a local datum to a water surface. Structural Measures are permanent Features constructed to affect the probability of flooding. Structural measures are a category of flood risk management tools that are separate from Nonstructural Measures Structural measures differ from nonstructural measures in that they focus on reducing the probability of flooding, as opposed to reducing the consequences of flooding. Subdivision Regulations help communities, as a part of Land Use Regulation, developing outside zoning areas by enabling legislation that allows control of public improvements needed along with the new subdivision, such as roads, utilities, and drainage facilities and floodplain areas. Tax Adjustments are a means of taxing. A tax is an amount of money that a government requires people to pay according to their income, the value of their property, etc., and that is used to pay for the things done by the government, like managing flood risks. Tax adjustments are measures that can be offered either to incentivize wise actions in flood risk management by individuals or communities, including multi-objective management measures such as green infrastructure, or to dissuade unwise actions.
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Temporary Flood Barriers are a form of Flood Proofing and help property owners manage flood risks, when enough warning time allows. These barriers can be free standing or may be affixed to openings on buildings. Property owners should check that any flood barriers have been tested by qualified professionals with the same consistent testing standards before use. See also Dry Flood Proofing. Tolerable Risks are risks that society is willing to live with so as to secure certain benefits; risks that society does not regard as something it might ignore; risks that society is confident are being properly managed by the owner; and risks that the owner keeps under review and reduces still further if and as practicable. Uncertainty is a term used by Risk professionals and accounts for the state of something not being well known. For Flood Risk, uncertainty may, for one example, mean a single value for the depth of floodwaters can be misleading, because the amount of rainfall runoff over a Basin varies and how much rain and how ground may soak up some suggests professionals should only communicate a range of depths to the public. Risk Assessments, which can take time and money, can help to narrow the range, however, uncertainty remains an important part of Risk Management. Wash is a term used for a stream in the bottom of many canyons in the western U.S. that have normally dry beds but may be very dangerous during a Flash Flood, because the floodwaters can be very deep and fast. Water Quality Enhancements are measures that help remove contaminants from water by filtering or otherwise providing treatments that reduce pollutants. These enhancements also tend to improve treatment of water quantity. Treating rain where it falls is the most cost effective measure for managing runoff. Watershed, or Basin, is all the area that drains rainfall from places higher, or upstream, of a point on land or along a stream or river. Wet Flood Proofing is a physical Nonstructural Measure for Flood Proofing buildings in the floodplain and is a measure that allows floodwater to enter the building, while vulnerable items such as utilities, appliances, and furnaces are relocated to higher locations. By allowing floodwater to enter the building hydrostatic forces on the inside and outside of the structure can be equalized reducing the risk of structural damage. Wetlands Protection and Restoration are any measure that may preserve and restore floodplains’ environmental quality, including Preserving the Natural Environment and Restoring the Natural Environment. Vulnerability is the characteristics of people and property that affect the likelihood that they will realize adverse consequences from exposure to the flood hazard. Zoning is a part of Land Use Regulation where a community divides a government unit into specified areas for use of buildings and land, height or bulk of buildings, size of lots, and density. Zoning is often associated with a community’s Comprehensive Plan and may be used for minimum finish floor elevations. Floodways and flood fringe are the typical minimum two zones used. Zoning is considered a nonphysical Nonstructural Measure.
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Appendix B: Dry Flood Proofing Example
(Representative of Commercial Structures in Study Area - Not an actual building) This enclosure considers the information required and the decisions needed to address flood risk for a stand-alone commercial building utilizing dry flood proofing. Structure Data:
One story masonry commercial building, dimensions 50 feet (front and rear) by 76 feet (sides).
Structure is freestanding. Floor area = 3800 square feet; Perimeter = 252 feet.
First floor elevation (wood floor) = 7510 feet NAVD88
Lowest ground elevation at front is 7509.5 feet and lowest ground elevation at rear is 7509.0 feet
Foundation is masonry with no exterior openings.
Full crawlspace with earth floor having elevation = 7507.0 feet NAVD88 – no utilities.
Three standard pedestrian doors (entrances). Window panes at least three feet above lowest floor.
Gas furnace and water heater located in first floor utility closet.
Air conditioning unit is exterior at ground level adjacent to side wall.
Gas meter and electric meter are exterior on rear wall. Electric panel is located in utility closet.
Flood Data: Flooding from street and at rear, potential for flows along sides from street to river at rear and shown on Figure B-1. The existing conditions building is shown in Figure B-2 and B-3.
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Figure B-1. Flooding at Example Building.
Base flood elevation at front (BFEf) = 7511.5 feet NAVD88. Base flood elevation at rear (BFEr) = 7511.1 feet NAVD88
The highest base flood elevation of 7511.5 feet is used to compute the flood proofing elevation. Flood depth front - BFEf minus lowest grade at front (7511.5 – 7509.5) = 2 feet.
Flood depth rear - BFEr minus lowest grade at rear (7511.1 – 7509) = 2.1 feet. Maximum design flood depth is 2.1 feet.
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Recommended Nonstructural Technique (Dry Flood Proofing):
The potential dry flood proofing considerations for this building are shown in Figures B-4 and B- 5.
Design dry flood proofing elevation = 7511.5 feet plus 1-foot freeboard = 7512.5 feet NAVD88,
Dry flood proof exterior walls to design flood proofing elevation. Design flood proofing elevation minus first floor elevation (7512.5 – 7510) equals 2.5 feet above first floor elevation.
Incorporate certified closures for the door openings to the design flood proofing elevation. Fill the crawlspace with uniform granular material to just below the floor joists.
Incorporate an anti-backflow valve on the sanitary sewer line.
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Incorporate a sump pump with emergency power supply, to be located at lowest elevation or in vicinity of closures.
Elevate the exterior air conditioning unit to the design flood proofing elevation.
Elevate gas meter to above the design flood proofing elevation and protect from debris impacts.
Flood Proofing Quantities: Flood proofing of exterior walls should extend below the first floor elevation to at least the adjacent ground elevation. For quantities, use maximum flood depth plus freeboard, (2.1 feet+1 foot) = 3.1 feet Flood proof walls with sealant on masonry – 3.1 feet x 252 feet = 781.2 square feet Apply brick veneer to protect sealant layer - 3.1 feet x 252 feet = 781.2 square feet. Door closures – 3 @ 2.5 feet high. Fill Crawlspace – 3,800 square feet x 2.5 feet = 9,500 cubic feet, 352 cubic yards Sump pump – 1 unit. Discharge pipe for sump pump – Length TBD by pump location Air conditioner platform – 1 Gas meter protection – 1
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An example of dry flood proofing applied to a non-residential, commercial, building is shown in Figure B-6. The water resistant sealant was applied to the exterior face of the building.
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Figure B-6. Brick Veneer applied over Water Resistant Sealant. A certified flood barrier door to complete the dry flood proofing is shown in Figure B-7, while Figure B-8 illustrates the finished project.
Figure B-7. Certified Flood Proof Entry Door.
Figure B-8 Completed Exterior portraying Dry Flood Proofing.
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Appendix C: Nonstructural Assessment Glossary 100 Year Flood – The 1% annual chance exceedance event expressed as a return period. Annual chance exceedance flood – The flood that has a (stated percent - %) chance of being exceeded in any given year, such as the 1% annual chance exceedance (ACE) flood. Breakaway Panel – A panel designed and constructed to collapse under water loads without causing collapse, displacement, or other structural damage to a building’s bearing walls or supporting foundation system. Base Flood Elevation (BFE) – Elevation of floodwaters for a 1% annual chance flood event. Base Flood Elevation plus free board (BFE+ X feet) - Equivalent to the elevation of floodwaters for a 100-year (1% annual chance) event plus X ft. of free board. Closures / Shields – Closures, as shown in C-1, act to close the openings and prevent water from entering. They can be of a variety of shapes, sizes, and materials. In some cases closures are permanently attached using hinges so that they can remain open when there is not a flood threat. They may also be portable and stored in a convenient location to slip into place when a flood threatens.
Figure C-1. Closure/Shields. Dry Flood Proofing involves temporarily or permanently sealing building walls with waterproofing compounds, impermeable sheeting, or other materials to prevent the entry of floodwaters into damageable buildings. Dry flood proofing, as shown in Figures C-2 and C-3, are applicable in areas of shallow, low velocity flooding
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Figure C-2. Permanent Dry Flood Proofing.
Figure C-3. Temporary Dry Flood Proofing. Elevation involves raising the buildings in place to reduce frequency and/or depth of flooding during high-water events. Elevation can be done on fill, foundation walls, piers, piles, posts or columns. Selection of proper elevation method depends on flood characteristics such as flood depth or velocity, and condition of the structure. Federal Emergency Management Agency (FEMA) – The agency within the Emergency Preparedness and Response Directorate of the U.S. Department of Homeland Security. FEMA facilitates coordination of Federal dam safety programs and administers the National Flood Insurance Program (NFIP) and several flood mitigation planning and grant programs. FIRM – Flood Insurance Rate Map, a product of the Federal Emergency Management Agency used to determine flood risk and insurance rates. Flood - A flood is an overflow of water that submerges land or buildings that are normally dry. Flood Insurance provides insurance to assist in recovery from a flood event. Typically not included with homeowner insurance policy. Flood Louver / Flood Vent/ Flood Openings – Flood louvers / flood vents are a permanent opening in a wall designed to allow unobstructed passage of water (automatically) in and out of a building thereby preventing water pressure buildup (hydrostatic pressure) that can damage or destroy foundations and bearing walls. Flood Risk - The likelihood and consequences that may arise from flood event.
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Flood Risk Management – Federal and non-Federal policies and programs for managing flood risk. This includes measures that reduce the flood hazard as well as measures that reduce the exposure and vulnerability of persons and property. Flood Risk Management Measures - These measures include implementation of reservoirs, detention storage, channels, diversions, levees, interior drainage systems, flood-proofing, levee raising, relocation of buildings/communities, and flood warning and emergency preparedness actions. It also includes policies and programs intended to inform and to influence the decisions made by Federal, state, and local government agencies, individuals, businesses and communities in their choice of flood risk reduction measures and to locate assets in floodplain. Flood-frequency – A graph, table, or single tabulation showing the relationship of the flood variable of interest (peak flow, peak stage, 3-hour volume, etc.) to the probability of the variable being exceeded in any given year. Foundation Vents – Foundation vents are permanent openings in foundation walls ventilation and unrestricted passage of air for ventilation of the crawl space. In wet flood proofing applications, additional foundation vents may be required to release air pressure changes caused by rising/falling water in confined spaces (crawlspace). Lowest Adjacent Grade (LAG) – The lowest ground elevation adjacent to the building. National Flood Insurance Program (NFIP) – Federal program under which flood-prone areas are identified and flood insurance is made available to the owners of the property in participating communities. Nonstructural Measures – Flood risk management measures that reduce the consequences of a flood event to a building by adapting the structure to the flood characteristics. National Nonstructural Committee (NNC) - The U.S. Army Corps of Engineers National Nonstructural Committee functions under the general direction of the Chief, Planning Community of Practice, Directorate of Civil Works, and HQUSACE. The objectives of the NNC are to: • Promote the development and use of all nonstructural flood risk reduction measures. • Risk expertise on all aspects of nonstructural flood risk reduction and associated opportunities. • Disseminate nonstructural flood reduction information • Partner with Planning Centers of Expertise in all aspects of nonstructural flood risk reduction and associated opportunities. • Provide leadership in all aspects of floodplain management Probability – Likelihood is a measure of the chance, or degree of belief that a particular outcome or consequence will occur. A probability provides a quantitative description of the likelihood of occurrence of a particular event. Relocation- involves moving the building to another location away from flood hazards. Relocation is the most dependable method of protection and provides the benefit of use of the evacuated floodplain. Return period – Alternate term ‘recurrence interval.’ The return period is the average time interval, usually expressed in years, between occurrences of an event of a certain magnitude. The return period is often computed as the reciprocal of the annual chance exceedance. Risk– Measure of the probability and severity of undesirable consequences. Structural Measures– Flood risk management measures such as dams, levees, and floodwalls focused on reducing flood hazard.
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Uncertainty – Used to describe any situations without sureness, whether or not described by a probability distribution. Wet Flood Proofing- measures that allow floodwater to enter the building. Vulnerable, items such as utilities, appliances and furnaces are relocated or waterproofed to higher locations. By allowing floodwater to enter the building hydrostatic forces on the inside and outside of the structure can be equalized reducing the risk of structural damage.
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Appendix D: Template for Annual Notice for Properties in Leveed Areas
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A template file is available to any state, county, or city that would like to alter this mailer for their own use.
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