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Flood Maps & Studies

The Federal Emergency Management Agency (FEMA) administers the National Flood Insurance Program and publishes flood maps and supporting flood insurance studies for over 750 communities in Ohio for the purpose of identifying areas at risk of the 1%-annual-chance flood, or base flood. In Ohio, ODNR Division of Water Resources is the State Coordinator of the National Flood Insurance Program. In terms of local floodplain management programs, possession and use of the appropriate FEMA floodplain map(s) and Flood Insurance Study is a participation requirement for all communities in the National Flood Insurance Program.

If you cannot find what you are looking for in FEMA's resources, contact your community's local floodplain administrator.

FEMA Resources

FEMA Map Service Center (MSC) is the official resource for all mapping products such as Flood Insurance Rate Maps (FIRM), Flood Insurance Studies (FIS), Letters of Map Change (LOMCs), Flood Risk Products, and preliminary and historical flood maps and studies. 

What Do Flood Maps Show?

The hazard area or, Special Flood Hazard Area (SFHA), shown on the flood map is known as the 100-year floodplain. It is more precisely defined as the floodplain associated with a flood that has a 1% annual chance of being equaled or exceeded in any given year. The 100-year flood is not a flood event that happens once in a hundred years, rather a flood event that has a 1% chance of occurring every year. Flood maps may include:

  • Major highways, secondary roads, lakes, railroads, streams and other waterways
  • Special Flood Hazard Areas (SFHA) identified on the FIRM as zones A, AE, AH, AO, AR, V, VE or A99
  • Base Flood Elevations (BFEs) or depths (BFE is the calculated elevation of the 100-year flood)
  • Areas subject to inundation by the 500-year flood (0.2%-annual-chance flood)

Flood Insurance Risk Zones

Zone A corresponds to the 100-year, or 1% annual chance, floodplain determined by approximate methods. Detailed hydraulic analysis is not performed for such areas, and no Base Flood Elevation (BFE) or depth is shown for this zone.

Zone AE and A1-A30 corresponds to 100-year, or 1% annual chance, floodplain that is determined in the Flood Insurance Study by detailed methods. Usually, BFEs derived from detailed hydraulic analysis are shown at select intervals within this zone.

Zone AH corresponds to areas of the 100-year, or 1% annual chance, shallow flooding with a constant water-surface elevation (usually areas of ponding) where average depths are between 1 and 3 feet. BFEs derived from detailed hydraulic analysis are shown at select intervals within this zone.

Zone AO corresponds to areas of the 100-year, or 1% annual chance, shallow flooding (typically sheet flow on sloping terrain) where average depths are between 1 and 3 feet. Average flood depths derived from detailed hydraulic analysis are shown within this zone.

Zone VE and V1-30 corresponds to areas subject to inundation by the 1%-annual-chance flood event with additional hazards due to storm-induced velocity wave action. Base Flood Elevations (BFEs) derived from detailed hydraulic analyses are shown. Mandatory flood insurance purchase requirements and floodplain management standards apply.

Zone V corresponds to areas along coasts subject to inundation by the 1-percent-annual-chance flood event with additional hazards associated with storm-induced waves. Because detailed hydraulic analyses have not been performed, no Base Flood Elevations (BFEs) or flood depths are shown. Mandatory flood insurance purchase requirements and floodplain management standards apply.

Zones B, C and X correspond to areas outside the 100-year or 1%-annual-chance floodplains, areas of 100-year sheet flow flooding with average depths less than 1 foot, areas of 100-year stream flooding where contributing drainage areas are less than 1 square mile, or areas protected from the 100-year or 1%-annual-chance flood by levees. No BFEs or depths are shown within these zones.

Map Changes

Letters of Map Change (LOMC) are letters which reflect an official change to an effective Flood Insurance Rate Map (FIRM). LOMCs are issued in response to a request to FEMA to revise or amend its effective flood map to remove a property or reflect changed flooding conditions on the effective map.  There are several types of LOMCs including: Letter of Map Amendment (LOMA), Letter of Map Amendment - Out as Shown (LOMA-OAS), Letter of Map Revision based on Fill (LOMR-F), Letter of Map Revision- Floodway (LOMR-FW) and Letter of Map Revision (LOMR).  LOMC applications are available for download at the link shown below.  For most LOMC applications, an applicant will need to hire a Professional Surveyor or Professional Engineer to acquire the necessary data and prepare the application. 

Periodically, FEMA will revise or update Flood Insurance Rate Maps (FIRM).  During this process, all LOMCs on the affected map panels will be reviewed to determine if the LOMC should be 1) incorporated into the revised panel; 2) superseded by new information used to prepare the revised panel; or 3) revalidated once the revised panel becomes effective.

Letters of Map Amendment (LOMA)

LOMAs are the most common type of mapping changes and are only applicable to changes that are the result of inadvertent inclusion due scale limitations and available topographic data. Please note that a LOMA cannot be obtained for a site and/or structure that is elevated on fill material; this would require a LOMR-F. A LOMA may only be obtained for a site and/or structure on natural grade. There is no fee for to apply for a LOMA.  LOMAs are not available for sites within the floodway.  Applicants may use the LOMR-FW process for a property in the floodway.  An MT-EZ application must be completed for a LOMA.

Conditional Letter of Map Amendment (CLOMA) is a letter from FEMA that states that the proposed structure on natural ground which is not elevated on fill will not be inundated by the base flood.  After the structure is constructed, the property owner must apply for a LOMA to formally change the FIRM.

Letter of Map Amendment- Out as Shown (LOMA-OAS)

LOMA-OAS is a determination made by the Federal Emergency Management Agency (FEMA) for a property and/or buildings as to whether it is located within the Special Flood Hazard Area (SFHA). This method is only used if it is clear, visually, that the structure in not in the SFHA.

Letters of Map Revision Based on Fill (LOMR-F)

LOMR-Fs are only applicable to mapping changes that are a result of a structure or parcel being elevated on fill above the Base Flood Elevation (BFE) An MT-1 application must be completed for a LOMR-F. All requests for changes to effective maps, other than those initiated by FEMA and LOMAs, must be made in writing by the Chief Executive Officer (CEO) of the community or an official designated by the CEO. Because LOMAs, LOMR-Fs, and LOMRs officially revise the effective NFIP map, they are public records the community must maintain. Any LOMR should be noted on the community's master flood map and filed by panel number in an accessible location. There is a fee to apply for a LOMR-F.  A completed Community Acknowledgement Form will be required for a LOMR-F submission.   A LOMR-F is not available within the floodway.  Applicants may use the LOMR-FW process for a property in the floodway.

Conditional Letter of Map Revision Based on Fill (CLOMR-F) is a letter from FEMA state that a parcel of land or proposed structure that will be elevated by fill would not be inundated by the base flood is fill is place on the parcel as proposed or the structure is built as proposed.  The letter does not revise an effective NFIP map, it indicates whether the project, if built as proposed, would be recognized by FEMA.  Any future development on the site must be “reasonably safe from flooding” and meet the criteria outlined in Technical Bulletin 10-01.  After the structure is built, the property owner must apply for a LOMR-F to formally change the FIRM.

Letter of Map Revision - Floodway (LOMR-FW)

LOMR-FW is used for any LOMCs proposed within the regulatory floodway. 

  • In situations where a building was constructed (or fill placed) before the area was delineated as Special Flood Hazard Area (SFHA), but the property is now depicted in the regulatory floodway on the Flood Insurance Rate Map (FIRM) – the MT-1 form should be used.  A copy of the FIRM in effect at the time of construction, current effective FIRM, and the Community Acknowledgement Form must be included with the submission.  No application fee is required. 
  • If fill was placed and/or a building was constructed on fill in a mapped SFHA fringe (not floodway), but it is now mapped within the floodway – the MT-1 form should be used.  A copy of the FIRM in effect at the time of construction, current effective FIRM, and the Community Acknowledgement Form must be included with the submission.  An application fee will be required. 
  • If fill was placed after the floodway was designated on the FIRM, a hydrologic and hydraulic analysis must be submitted with the request.  If the hydraulic and hydrologic analysis is not provided, the LOMR-FW request will be identified by FEMA as a potential violation.

Letter of Map Revision (LOMR)

A Letter of Map Revision (LOMR) is FEMA's modification to an effective Flood Insurance Rate Map (FIRM), or Flood Boundary and Floodway Map (FBFM), or both. LOMRs are generally based on the implementation of physical measures that affect the hydrologic or hydraulic characteristics of a flooding source and thus result in the modification of the existing regulatory floodway, the effective Base Flood Elevations (BFEs), or the Special Flood Hazard Area (SFHA). The LOMR officially revises the Flood Insurance Rate Map (FIRM) or Flood Boundary and Floodway Map (FBFM), and sometimes the Flood Insurance Study (FIS) report, and when appropriate, includes a description of the modifications. The LOMR is generally accompanied by an annotated copy of the affected portions of the FIRM, FBFM, or FIS report.

All requests for changes to effective maps, other than those initiated by FEMA, must be made in writing by the Chief Executive Officer (CEO) of the community or an official designated by the CEO. Because a LOMR officially revises the effective NFIP map, it is a public record that the community must maintain. Any LOMR should be noted on the community's master flood map and filed by panel number in an accessible location. An MT-2 application must be submitted to FEMA for all LOMRs.

A Conditional Letter of Map Revision (CLOMR) is FEMA's comment on a proposed project that would, upon construction, affect the hydrologic or hydraulic characteristics of a flooding source and thus result in the modification of the existing regulatory floodway, the effective Base Flood Elevations (BFEs), or the Special Flood Hazard Area (SFHA).  The letter does not revise an effective NFIP map, it indicates whether the project, if built as proposed, would be recognized by FEMA. FEMA charges a fee for processing CLOMR requests.  Once a project has been completed, the community must request a revision to the Flood Insurance Rate Map (FIRM) to reflect the project. "As-built" certification and other data must be submitted to support the revision request.

  • A CLOMR is required if the hydrologic and hydraulic analysis shows that the BFE would be increased by the project.
  • The current effective model must be used when performing the analysis.

How to View a LOMC

Most LOMCs can be downloaded from the Map Service Center, however, some older LOMCs may not be available from the site.  ODNR has a comprehensive database of Letters of Map Change, which are available upon request.

Mapping Programs

Risk MAP

Risk Mapping, Assessment, and Planning (Risk MAP) is a new Federal Emergency Management Agency (FEMA) program that provides communities with updated flood hazard information and risk assessment tools they can use to enhance their mitigation plans to better protect their citizens. Through more accurate flood maps, risk assessment tools, and outreach support, Risk MAP builds on Map Modernization and strengthens local ability to make informed decisions about reducing risk. Risk MAP uses a watershed-based study approach which improving engineering credibility and allows for the understanding of risks in a more comprehensive way.

Principles of Risk MAP

  • Mapping – Identification of Flood Hazards and Risk
  • Assessment – Gather Local, State and Federal information to assess the potential flood risk
  • Planning – Use the data obtained through Risk MAP to update Hazard Mitigation Plans which will lead to better mitigation actions

Risk MAP Goals

  • Address gaps in data to ensure quality flood hazard data
  • Promote better public awareness and understanding of flood risk
  • Inspire mitigation actions that reduce risk
  • Provide an enhanced digital platform that improves communication and sharing of risk data
  • Increase collaboration between local, state and federal partners

Risk MAP Life Cycle

The Risk MAP life cycle can range from three to five years. During that time there are at least four community meetings.

  • Discovery- Identification of local community flood hazard mapping needs, data availability and areas of mitigation interest
  • Flood Risk Review- Review and discuss mapping project data assumptions
  • Resilience- Discuss incorporating Risk MAP data in local mitigation plans and opportunities for mitigation project development with communities
  • Open House- Review and receive comments on preliminary floodplain maps from local officials and citizens. Answer questions about potential impacts

Floodplain Mapping — Non-Regulatory Products

As FEMA transitions from the Map Modernization program to the Risk Mapping, Assessment, and Planning (Risk MAP) program, there are new ways to use the data from Map Modernization to help communities identify potential hazards. Through the Risk MAP, FEMA has developed several non­ regulatory products that can assist communities with community planning, outreach, and education. These products can further identify where flooding may take place within a community. Developing additional locations could be used to help prioritize potential mitigation actions within the community.

The non-regulatory products are grouped into two categories: Basic and Enhanced. Basic products will be produced for every Risk MAP project while enhanced products will be produced if there is data available to support their development.

Basic Products and Datasets

Flood Risk Map / Flood Risk Dataset / Flood Risk Report

The Flood Risk Report provides stakeholders with a comprehensive understanding of flood hazard and risk exposure within their community, watershed, or county. The report parallels the Flood Insurance.

Study report by providing a narrative of the flood risk assessment methodology and results. The report provides risk assessment information at the project level, placing emphasis on risk reduction activities that may have impacts beyond the specific stream area or community. The report will also provide risk assessment information that can be incorporated into mitigation plans. The report will also include a Flood Risk Map that depicts select flood risk data for jurisdictions within the project area, emphasizing that risk reduction activities may have an impact beyond the site.

The Flood Risk Database will be the primary source to access information collected and developed during the flood risk assessment process. The Flood Risk Database parallels the Flood Insurance Rate Map database. It is a project­level database that includes flood risk assessment data collected, created, and analyzed during the flood risk project. FEMA will publish and maintain the database in a standardized form to support national, state, regional, and local distribution. Viewing tools are currently under development, to provide users without access to Geographic Information System (GIS) software, the ability to visualize and understand the multiple flood risk datasets contained within the database.

Flood Risk Assessment

Flood Risk Assessments helps guide community mitigation efforts by highlighting areas where risk reduction actions may produce the highest return on investment. Building on the foundation of the 2010 nationwide HAZUS Level 1 Average Annualized Flood Loss (AAL) Study, basic refined HAZUS loss estimation analyses will be done for flooding sources with default HAZUS building stock information. Where local built environment data is available, enhanced HAZUS or other risk assessment analyses are possible. Communities are encouraged to pursue enhanced analysis where possible by providing FEMA with additional GIS data such as parcel data, building footprints, or elevation certificates. Communities may also provide additional funding to support analysis enhancement. The results of both the basic refined and enhanced HAZUS analysis can be incorporated into hazard mitigation plans.

Changes Since Last FIRM (CSLF)

The Changes Since Last FIRM dataset helps communities understand changes to their flood maps and prepare for the upcoming flood map adoption process. This product is a spatial dataset that identifies areas of floodplain and flood zone changes that have occurred since the previous flood map study. The dataset captures areas where the floodplain and floodway have increased or decreased, as well as areas where the flood zone designation has changed (e.g., A to AE). In areas where the mapped flood hazard has changed, the engineering factors that may have contributed to that change will also be identified within the dataset. The built environment affected by the change is quantified and summarized to help locate previously unidentified areas at risk.

Depth and Analysis Grids

Depth grids provide the depth of flooding for the 10% (10-yr), 4% (25-yr), 2% (50-yr), 1% (100-yr), and 0.2% (500-yr) annual chance flood events. This product is developed by subtracting the water surface elevation from the ground elevation at a given point for any given flood event. Better topography data will result in more accurate depth grids. The depth grids help people to understand not just whether their house is "in" or "out" of the floodplain but how deep the flooding will be in their area for a given flood event. The analysis grids will be used to create additional analyses that depict the percent annual chance of flooding and the percent chance of flooding over a 30-­year period in the floodplain. This product will visually depict levels of risk within the Special Flood Hazard Area.

Enhanced Products

Where data is available, there are several Enhanced products that can be requested by the local community. The dam­related products are intended to be used by the dam owner/operator, emergency management officials, and planners. These products would depict upstream impoundment areas, downstream inundation areas from a partial or full release, depth grids, flood velocity, and estimated time of flood wave arrival. This information could be used to identify structures and critical facilities that may warrant consideration for mitigation projects.

Areas of Mitigation Interest (AOMI)

The Areas of Mitigation Interest dataset helps communities better understand the impact of multiple physical factors on the floodplain elevation and extent. An AOMI identifies areas that would benefit from mitigation measures such as repetitively flooded structures, undersized culverts, emergency routes historically impacted by flooding, and significant erosion areas.This enhanced spatial dataset, identifies conditions within a flood risk project area (watershed or otherwise) that may contribute to the severity of the flood hazard and associated losses. These conditions include areas with a history of flood claims, hydraulic or other structures that contribute to backwater (e.g., undersized culverts, bridges and dams), and areas experiencing land use change or development. By identifying these conditions within the watershed, this product will also assist communities in determining potential mitigation opportunities. If your community has any AOMIs, they can be entered online on the State Hazard Analysis Resource and Planning Portal (SHARPP) website.

Coordinated Needs Management Strategy

The Coordinated Needs Management Strategy (CNMS) defines an approach for the identification and management of flood hazard mapping needs and requirements that will provide support to data-driven planning and the flood hazard information production planning process. Floodplains inherently change over time, which is a characteristic that makes their management and mapping a challenge. The underlying concern is that there will be an unending supply of mapping needs due to the changing nature of the physical environment, climate patterns, and engineering methods. The CNMS Database is available to communities for review and comments. Please contact the Floodplain Management Program to request the CNMS database.

Components

  • Steam study inventory
  • Validation process documentation
  • Documents local and state needs and requests. for studies to be updated

What CNMS does

  • Tracks needs, requests and study status in a GIS format
  • A tool used to report, project and predict New, Valid or Updated Engineering (NVUE) statistics
  • A tool to assist with Risk MAP Discovery
  • Import component to multi-year and specific project planning

Benefits of CNMS

The CNMS is intended to improve efficiencies in communication, documentation, analysis, planning, tracking, and reporting of floodplain mapping needs. Using Geographic Information Systems (GIS) technology to allow for spatial analysis as an effective means to visualize, enter, review, and update a needs inventory. By standardizing and storing data in a geospatial format, CNMS will accomplish the objectives of maintaining current data in a readily available format for improved analysis and reporting.

Validation of Flood studies

The review and analysis of flood studies consist of critical and secondary elements (see table below). There are seven critical elements reviewed to assist in the validation of each flood study. If any one of these critical elements is evaluated to be “Yes” as a result of the identification of a deficiency, it is significant enough to trigger an “Unmet Need” validation status. There are ten secondary elements reviewed to assist in the validation of each flood study. If four or more secondary elements are evaluated to be “Yes” as a result of the identification of a deficiency, that is sufficient to trigger an “Unmet Need” validation status. Please see the inset table detailing the critical and secondary elements considered in this review. The “Unmet Need” validation status signifies that a flood study may no longer provide an accurate representation of the flood risk and suggesting the need for an updated study.

CNMS Elements

CRITICAL

  1. A major change in gage record since the initial FIRM
  2. Updated and effective peak discharge differ
  3. Model methodology no longer appropriate
  4. Addition/Removal of major flood control structures
  5. Current channel outside of effective SFHA
  6. Addition/removal of >5 hydraulic structures
  7. Significant channel fill or scour

SECONDARY

  1. Use of rural regression equations in urban areas
  2. Repetitive losses outside of SFHA
  3. Addition/removal of <=5 hydraulic structures
  4. Increase in the impervious area in sub-basin more than 90%
  5. Channel improvements/shoreline changes
  6. Availability of better topography data
  7. Changes to vegetation or land use
  8. Failure to identify primary dune in coastal areas
  9. Significant storms with high watermarks
  10. New regression equations

Cooperating Technical Partners (CTP)

Cooperating Technical Partners (CTPs) are state, regional, or local agencies/communities that have an interest in becoming involved with FEMA's flood map update. Potential CTPs should have the capabilities and resources necessary to be active participants in this program. Such involvement results in better, more accurate maps that may reflect unique characteristics of their community. Furthermore, map products are optimized when FEMA and the respective partner set specific goals and combine resources to meet them.

Benefits of such a partnership are numerous. First, CTPs help create more accurate maps than an independent agency (i.e. FEMA), and they facilitate faster map updates. Also, information that is used for planning and permitting will become a key component for the maps developed, which can assist in better floodplain management. Finally, community CTPs can receive Community Rating System credits for their involvement. These credits can lead to discounted flood insurance premiums for property owners in the community. Funding for CTP mapping projects are limited through FEMA. One objective of this program is to leverage available funding to attain more mapping for the same amount of resources. However, some funding is available for certain mapping activities. This funding is managed by FEMA regional offices and can be obtained through a cooperative agreement. Funded activities include:

  • Refinement of approximate Zone A boundaries
  • Hydrologic and hydraulic analyses and floodplain mapping
  • Coastal floods hazard analyses and floodplain mapping
  • Digital Flood Insurance Rate Map (DFIRM) preparation
  • Redelineation of detailed flood hazard information using updated topographic data
  • Digital topographic data development
  • Scoping up to 10%
  • Post preliminary processing
  • Outreach

Even though funding may not be available for these activities, FEMA may provide the CTP with support data and/or technical assistance. Non-funded activities include:

  • Base map inventory development
  • Digital base map data sharing
  • DFIRM maintenance
  • Hydrologic and hydraulic review
  • Analysis of community map update needs
  • Technical standards adoption

Types of CTP Agreements

There are three types of agreements available under the CTP Initiative:

  1. Partnership Agreement
  2. Mapping Activity Statement
  3. Cooperative Agreement

The Partnership Agreement formalizes the partnership with FEMA, and it highlights the importance of flood hazard identification, flood insurance, and floodplain management. Overall, it indicates that the partner and FEMA will work together on the update of flood maps. You may view a template for this agreement, and an example by downloading the below PDF documents.

A Cooperative Agreement must be obtained for federal funding of a particular mapping activity. Locally funded activities can be initiated at any time without such an agreement.

Current Ohio CTPs

Partner: Ohio Department of Natural Resources
Primary Contact: Katherine Goeppner, (614) 265-6709
Mapping Activities Undertaken:

  1. Digital Flood Insurance Rate Map (FIRM) Preparation
  2. Risk MAP projects for Cuyahoga, Huron-Vermilion, Licking, Little Scioto-Tygarts and Upper Ohio Shade Watersheds.

Partner: Ohio Department of Public Safety, Emergency Management Agency Mitigation Branch
Primary Contact: Steve Ferryman- State Hazard Mitigation Officer, (614) 799-3539

National CTP List

Map Modernization

Prior to Map Modernization, many communities throughout Ohio had flood maps that were 10-30 years old, and many of these maps did not reflect the current flooding conditions of their particular areas. Such outdated maps directly affected flood risk management, potentially putting more citizens at risk of sustaining losses of property or lives.

FEMA’s Flood Map Modernization initiative was a nationwide, $1 billion effort to modernize the nation’s inventory of flood maps. During this update, the maps were produced in a seamless, countywide format. The digital flood layer that was generated is compatible with most Geographic Information Systems (GIS) and Auto-CAD platforms. Thus, local communities can utilize this digital data in conjunction with other data (such as parcel data) in order to enhance their local floodplain management programs.

 

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