Floodplain Management

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Floodplain Management

Floodplain management are the corrective and preventative measures for reducing flood damage. These measures are adopted by state and local governments so that the citizens in the community will be eligible to purchase flood insurance.

National Flood Insurance Program

The NFIP is a federal program enabling property owners in participating communities to purchase insurance protection against losses from flooding. This insurance is designed to provide an alternative to government assistance to meet the escalating costs of repairing damage to buildings and replacing properties lost as a result of flooding. If a community adopts and enforces a floodplain management ordinance to reduce future flood risks to new construction in Special Flood Hazard Areas, the federal government will make flood insurance available within the community.

A list of NFIP Guidance Material Essentials (PDF) can be utilized to find relevant information available on the NFIP, including technical bulletins, templates, forms, links, documents, and training resources.

A new federal law, the Biggert-Waters Flood Insurance Reform Act of 2012, will change flood insurance rates. Expected changes to the flood insurance program are explained in Analysis of Expected Changes to the Flood Insurance Program (PDF).

Floodplain Mapping Program

In cooperation with the Federal Emergency Management Agency (FEMA), the State developed the Floodplain Mapping Program to aid FEMA's Flood Hazard Mapping. New York State Preliminary Floodplain Maps and mapping status updates are available in the important links section below.

Reducing Flood Damage - State and National Information Resources

Click the links to state and national associations like the Association of State Floodplain Managers (ASFM) and the New York State Floodplain and Stormwater Managers Association for guidance on floodplain management policy and practice.

The ASFM's "No Adverse Impacts Toolkit," offers local governments a way to prevent the worsening of flooding and other negative impacts on the community.

Do You Need Assistance?

For further assistance on floodplain development requirements, please call your regional DEC floodplain management official, or DEC's Floodplain Management Section in Albany at 518-402-8185. A complete list of Floodplain Management Coordinators (PDF) is available for your convenience. 

Flood Response and Substantial Damage in New York State

NYSDEC Floodplain Management Section has developed NYS specific substantial damage resources to support communities in their post disaster response. Included is a New York Flood and Substantial Damage Quick Guide for community officials, a Substantial Damage Management Plan Template, and fillable forms and letters. 

Learn More

Floodplain Management Guidance

Floodplain Management Requirements for Water Quality Improvement Project (WQIP) Program Resources

For those applying to the 2021 WQIP program, please see the guidance below for any projects located within an Enhanced Flood Hazard Area, Enhanced Coastal High Hazard Area, or the 0.2% floodplain. Get more information about the WQIP Program.

If the project is within an Enhanced Flood Hazard Area, Enhanced Coastal High Hazard Area, or the 0.2% floodplain, the following information must be provided:

  • A floodplain map with the location of the project indicated;
  • A site plan with the contours indicating the Enhanced Flood Hazard Area, Enhanced Coastal High Hazard Area, or the 0.2% floodplain;
  • Location and elevation of non-critical and critical equipment (if applicable to project);
  • Certification of floodproofing (if applicable to project) and;
  • A floodway analysis with a no-rise certificate if the project is within a regulated floodway.

For additional guidance and information to meet the above requirements please review the following:

  • The FEMA Map Service Center for available Flood Insurance Rate Maps (FIRMs). Communities with mapping dated to 1978 to 1986 may have the floodways delineated on a separate map panel. This critical information is not shown when searching by address on FEMA's Map Service Center. To check for separate floodway panels, search all products for a community.
  • To determine the Enhanced Flood Hazard Area and additional flood risk considerations please review the NYS Flood Risk Management Guidance for Implementation of the Community Risk and Resiliency Act.
  • For Wastewater Treatment Improvement projects please review TR-16 Guides for the Design of Wastewater Treatment Works. This guide must be considered in the design of wastewater treatment and is newly revised to reflect the need for resiliency in the face of storm surge and extreme weather.
  • Non-residential structures located within the Flood Hazard Area have the option to floodproof instead of elevating. FEMA's Technical Bulletin 3 provides guidance on the NFIP floodplain management requirements for the design and certification of dry floodproofing.
  • Any development within a regulatory floodway, as indicated on a community's FIRM or Flood Boundary and Floodway Map, requires a hydraulic analysis to demonstrate "no-rise" in flood levels as a result of the project before a floodplain development permit can be issued. Requests for modeling can be sent to [email protected] - please include the community and stream reach needed with the request.

Note: Floodplain management is locally administered, any development within a FEMA identified Special Flood Hazard Area requires a local floodplain development permit from the municipality with jurisdiction. This is in addition to any other necessary local, State, or Federal permits or approvals. Being awarded funding or issued a DEC permit does not remove the requirement for a local floodplain development permit.

Joining the National Flood Insurance Program

The National Flood Insurance Program is a Federal program enabling property owners in participating communities to purchase insurance protection against losses from flooding. This insurance is designed to provide an insurance alternative to disaster assistance to meet the escalating costs of repairing damage to buildings and their contents caused by floods.

Participation in the National Flood Insurance Program is based on an agreement between local communities and the Federal Government that states if a community will adopt and enforce a floodplain management ordinance to reduce future flood risks to new construction in Special Flood Hazard Areas (100-year floodplain, or areas subject to a 1 percent or greater chance of flooding per year), the Federal Government will make flood insurance available within the community as a financial protection against flood losses. If communities do not participate in the National Flood Insurance Program then insurance companies can not write policies for that community and federally regulated lending institutions are prohibited from issuing mortgages for properties within mapped Special Flood Hazard Areas as depicted on the Flood Insurance Rate Map.

Currently, the majority of New York State communities with mapped flood hazard areas are already in the National Flood Insurance Program. There are also many communities which do not have maps that participate so that their residents may have access to flood insurance.

In order to join the National Flood Insurance Program a municipality simply needs to pass a resolution indicating that it is interested in joining the program, fill out an application (see right column of this page) and adopt the necessary flood damage prevention local law to be approved by the New York State Department of Environmental Conservation and the Federal Emergency Management Agency. This local law indicates that if a community has mapped flood hazard areas and if development is to occur in those flood hazard areas then the development is required to be built to certain standards, identified in the National Flood Insurance Program's regulations (44 CFR 60.3) and the New York State Building and Residential Codes. If development is being considered for a Special Flood Hazard Area, then the local floodplain administrator, an office designated in the local law, reviews the development to ensure that construction standards have been met before issuing a floodplain development permit. Non-structural development within a Special Flood Hazard Area is also subject to a local floodplain development permit.

DEC has three model local laws for flood damage prevention that communities can adopt to join the program: one for communities without mapped flood hazards, one for communities with standard mapped flood hazards, and another for communities with coastal flood hazard areas. Materials needed to join the National Flood Insurance Program are listed in the right-hand column on this webpage. If your community would like more information on joining the program please contact the floodplain management section at the number also listed in the right-hand column.

To request the Model Flood Damage Prevention Law appropriate for your community, please email the DEC Floodplain Management Section or call 518-402-8185.

Floodplain Development and Floodway Guidance

Purpose

The purpose of this guidance is to provide aid in those situations when floodplain development is proposed and the intent of the project is to meet the "no-rise" and/or "no adverse effect" criteria by using the effective hydraulic model, but not to revise the flood maps. Under those conditions the analysis can be reviewed at the local or state level, and the Federal Emergency Management Agency (FEMA) need not be involved. If changes to the maps are required, such as a change in base flood elevation (BFE), or the extent of the special flood hazard area (SFHA), or the location of the floodway, then a request must be submitted to FEMA for a map change.

"No-Rise" versus "No Adverse Effects"

There is a two-tiered system of technical evaluation for proposed development in the floodplain. All proposed floodplain development must meet the "no adverse affect" criteria, while proposed floodway development must also meet the "no-rise" criteria. For streams with detailed studies/AE-zones, the 100-year floodplain has been divided into two zones, the floodway and the floodway fringe. The floodway is that area that must be kept open to convey flood waters downstream. The floodway fringe is that area that can be developed in accordance with FEMA standards as adopted in the local law.

"No-Rise" Any proposed development within the floodway requires a hydraulic analysis performed by a qualified registered professional engineer (PE) to demonstrate "no-rise." "No-rise" is defined as a 0.00-feet difference in the computed BFE's at each modeled cross-section. The determination of "no-rise" would normally be demonstrated by comparing the natural run, base flood elevations (BFE) as listed in the output of the Pre-project and Post-project Models. See Table 1 - Comparison of BFEs, for an example. Using such a table, the differences stemming from each successive modeling step can be clearly seen, then the reasons for those differences can be adequately justified and documented.

Table 1-Comparison of BFE's
profile Section LabelModel Section #Effective ModelDuplicate Effective ModelDup-EffPre-project ModelPre-DupPost-project ModelPost-Pre
F52351325.331325.330.001325.330.001325.330.00
 52651325.381325.380.001325.380.001325.380.00
 53301325.481325.480.001325.480.001325.480.00
G55101325.821325.830.011325.860.031325.860.00
 55801325.771325.790.021325.780.001325.780.00
 56201325.871325.880.011325.900.031325.900.00
H58201326.491326.46-0.031326.630.161326.630.00
 6225   1327.00 1326.97-0.03
 6306   1326.95 1326.89-0.06
 6387   1326.90 1326.82-0.07
 6468   1326.86 1326.80-0.05
 6549   1327.15 1327.340.19
I66301327.191327.270.081327.480.211327.600.12
 75401329.091329.290.201329.480.191329.620.14

When attempting to use the procedure described below to satisfy the "no-rise" requirement, the entire proposed development should be added to the Post-Project model, regardless of whether it is in the floodway. The no-rise analysis with appropriate mitigation should be completed, as appropriate, prior to starting a no adverse effects analysis.

"No Adverse Effects" The local Flood Damage Prevention law defines "adversely effected" as any physical damage to an adjoining or other property. It is not the intent of the National Flood Insurance Program regulations to require a detailed engineering analysis for all developments within the floodway fringe. However the local floodplain administrator may require a "no adverse effect" analysis for larger projects that can potentially result in physical damage to other property.

One method of determining if an adverse effect would occur is to compare the BFE's as listed in the output of the Pre-Project and Post-Project Models. When attempting to use the procedure described below to satisfy the "no adverse effects" requirement, both the mitigated floodway development and the proposed floodway fringe development should be added to the Post-Project Model. Then any rise in BFE can be attributed to the portion of the proposed development that falls in the floodway fringe, which by definition should be less than 1-foot. In any area where there is an increase in BFE, the lowest adjacent grades (LAG) at all potentially affected structures in the area could be surveyed, and if a structure's LAG was below the BFE resulting from the proposed development, then it could be assumed that water would enter and damage that structure and/or its contents. Any such identified adverse effects would then be mitigated as a condition of the floodplain development permit. There is a wide variety of technical publications available from FEMA and the US Army Corps of Engineers that discuss the range of mitigation techniques that are available.

Ultimately, it is the responsibility of the local Floodplain Administrator (FPA) to determine what form of technical evaluation is acceptable. However, it should be noted that NYSDEC has Regional Floodplain Coordinators who are available to provide advice and technical support for specific floodplain development situations. In general, if the FPA has any doubt whether the "no-rise" and no adverse effect criteria can be met, then the applicant should be required to conduct a hydraulic analysis using the effective model. Such a hydraulic analysis, when properly developed, is considered to be both definitive and defensible.

Authority

In general, the authority for requiring a hydraulic analysis to satisfy the "no-rise" criteria stems from 44 CFR Part 60.3(d)(3) which states that where a regulatory floodway has been designated the community shall: "Prohibit encroachments, including fill, new construction, substantial improvements, and other development within the adopted regulatory floodway unless it has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practices that the proposed encroachment would not result in any increase in flood levels within the community during the occurrence of the base flood discharge." Specific State authority to require a "no-rise" analysis (for State-owned and State-funded projects, only) stems from 6 NYCRR Part 502.4(b). Local authority stems from Article 36 of the Environmental Conservation Law (ECL), as well as various provisions in the applicable local law for flood damage prevention, which are based on FEMA minimum standards, and require technical evaluations for "no-rise" and "no adverse effect." While a hydraulic analysis is considered an option for satisfying the "no adverse effects" criteria for proposed development solely in the floodway fringe, it may be unreasonable to require such an analysis for anything but a large development with a large quantity of fill.

Hydraulic Modeling Software

Historically, HEC-2 was the most commonly used software for hydraulic modeling in flood studies. FEMA now encourages the use of the software package known as HEC-RAS for new flood studies. The conversion of effective studies from HEC-2 into HEC-RAS is also encouraged. However, it should be noted that FEMA does accept models developed using other software packages, when appropriate. A list of accepted hydraulic modeling software packages can be viewed at: http://www.fema.gov/fhm/en_modl.shtm

It should be noted that there is a difference between a hydraulic model and the software package used to develop a model. A software package generally includes the algorithms used to perform the calculation, along with any associated input and output interfaces. A "model" is the input file containing the flow rate and channel geometry information for a specific study reach, which is used with the software to simulate how that reach would respond to a specific set of flood conditions.

Recommended Procedures

The following is a summary of recommended procedures for use in updating an effective study to reflect changed and/or proposed conditions. By using this procedure, the effects of model changes at each step can be properly documented and isolated, so that ultimately, only the effects of the proposed development are considered.

Special Circumstances

From time to time, situations such as changed flow conditions or undocumented, man-made changes are discovered. As the available period of record grows for gauge data, or as better hydrologic techniques are developed and applied, significant changes in flows can be encountered during the modeling process. Ideally, any man-made modifications to the floodplain will have been documented through the map revision process. However, significant undocumented, man-made changes are sometimes also discovered during the modeling process.

Care should be taken to incorporate these conditions into the analysis in an acceptable manner. When either of these conditions is encountered, the appropriate map revisions must be requested by the community. However, if these undocumented changes are not the result of a previous action on the part of the developer, then the developer should not be penalized for circumstances that are outside of his/her control. The developer can then either wait for the required map revisions to be implemented (a process which may take several months, or more), or the developer can proceed with a two-scenario approach.

The first scenario would use the Corrected Effective Model to represent the pre-project conditions without the flow changes and/or undocumented, man-made changes included, and would serve to meet the requirements of the current regulatory standard in effect in the community. The second scenario would convert the Corrected Effective Model into a Pre-Project Model by incorporating the flow changes and/or undocumented, man-made changes that have been discovered. The second scenario would serve to meet the requirements of a theoretical, "corrected" version of the regulatory standard. Both scenarios would be developed in parallel based on the same Effective, Duplicate Effective and Corrected Effective Models, and each scenario would be carried through the Post-Project Conditions Model and the Post-Project with Compensatory Actions Model, as appropriate. Both scenarios must separately satisfy the "no-rise" and "no adverse effect" criteria.

The effective model is the basis of the current regulatory standard in effect for a community, and serves as the starting point for the modeling of any proposed development in the floodplain. Ideally, the Effective Model will include the "natural run" (resulting in the 10-, 50-, 100-, and 500-year water surface profiles), which is used to define the extent of the floodplain, and the "encroachment run," which is used to divide the floodplain into the floodway and the floodway fringe. It should be noted that the Effective Model often includes more cross sections than are shown on the Flood Insurance Rate Map (FIRM), Flood Boundary and Floodway Map (FBFM) and Flood Insurance Study (FIS). If an FIS has been published for the community and base flood elevations are shown on the FIRM covering the site, the effective model is likely to be available, at no charge from this office. If we don't have it, then we can provide the procedures for requesting that information from FEMA. We can also provide procedures on what to do if the Effective Model cannot be recovered.

Copies of the hydraulic model used in the effective FIS, referred to herein as the Effective Model, must be obtained and then reproduced on the requester's equipment/software, thus creating the Duplicate Effective Model. The same equipment and software should be used for all succeeding modeling steps. The documentation of this step is required to assure that the Effective Model's input data has been transferred correctly to the new equipment/software and to assure that the revised model will be integrated into the effective data to provide a continuous water surface profile both upstream and downstream of the revised reach. The differences in the water-surface elevations between the Effective and Duplicate Effective Models must be fully documented and thoroughly explained. The entire Effective Model may not need to be recreated. 

Differences between the Effective and Duplicate Effective models can often be attributed to computational differences between succeeding versions of the model software, such as: (1) differences in bridge/culvert modeling routines, (2) method of conveyance calculations, (3) critical depth default, and (4) floodway computations.

The HEC-RAS User's Manual and the HEC-RAS Hydraulics Reference Manual provide details on computational differences between the HEC-2 and HEC-RAS and guidance on simulating HEC-2 results; such manuals should be consulted to explain the differences between the Effective and Duplicate Effective Models. The HEC-RAS software and manuals can be downloaded from the internet at: http://www.hec.usace.army.mil/

Another useful reference is FEMA's "HEC-RAS Procedures for HEC-2 Modelers," dated April 2002. This publication can be downloaded from the internet at: http://www.fema.gov/fhm/dl_fpmm.shtm

The Corrected Effective Model corrects any modeling errors that exist in the Duplicate Effective Model, adds any additional cross sections to the Duplicate Effective Model required to represent the proposed project, incorporates natural changes in the floodplain (such as stream meandering), and incorporates more detailed topographic information than that used in the Effective Model.

An error could be a technical error in the modeling procedures (such as improperly addressed or ignored warning and error messages), or any development in the floodplain that occurred prior to the effective date of the study, but was not incorporated into the effective model. Changes in structures or vegetation would be reflected in updated n-values. Changes in the floodplain geometry, such as cut or fill, would be reflected in the cross-section. The Corrected Effective Model must not reflect any man-made physical changes since the date of the effective model.

All cross-sections that are required to represent the proposed development should be added during this step. The number and location of cross-sections in the model should remain constant for all remaining steps. The cross-section should represent all significant breaks in slope along the section. Ideally, the collection of new cross-section information will be supervised and certified by a surveyor, engineer or architect who is licensed in New York State. However, cross-sections compiled from available information may be acceptable, if suitably justified and documented. When adding cross-sections, the roughness coefficients (Manning's n-values) for the reach should remain the same, unless a reasonable explanation of why they should be changed is included in the supporting data. The cumulative reach lengths should also remain the same, unless justified and documented.

Note: If it becomes necessary to revise the floodway run, the effective encroachment stations must be retained for those cross-sections that were in the Effective Model. Ideally, encroachment stations for any new cross-sections that are added, should be developed by performing a linear interpolation between the cross-sections immediately upstream and downstream, as included in the Effective Model. If the Effective Model is not available, then the encroachment stations can be approximated by scaling the effective floodway width off of the FIRM or FBFM. Estimated encroachment stations should be confirmed by completing a floodway run, and ensuring that the surcharge (the rise in water surface elevation between the natural and encroachment runs) is no more than 1-foot anywhere along the profile. The estimated encroachment stations must be adjusted until this 1-foot surcharge criteria is met.

Under the second scenario of a two-scenario approach, the Corrected Effective Model is modified to reflect any changed flow conditions and/or undocumented, man-made changes that have occurred within the floodplain since the effective study was adopted, but prior to the construction of the project for which the revision is being requested. If no changed flow conditions or undocumented, man-made changes have been identified, then this model would be identical to the Corrected Effective Model.

The Pre-Project Conditions Model (or Duplicate Effective or Corrected Effective Model, as appropriate) is revised to reflect post-project conditions. This model must incorporate any physical changes to the floodplain since the effective model was produced as well as the effects of the project. Depending on the circumstances of the project, the applicant may be requested to mitigate to an earlier condition, as represented by the Corrected Effective or Duplicate Effective Models. Output values should be limited to two decimal places. In some cases, the proposed development may result in "no-rise," but will result in increases in water velocity. Such increases may also require mitigation. The Post-Project Model must merge with the effective water-surface profile, to within +/- 0.5-feet at the upstream and downstream ends of the revised reach, in compliance with 44 CFR Part 65.6(a)(2).

If a rise results from a proposed development, then subsequent model runs should be developed to represent the impacts of any proposed compensatory action and demonstrate compliance with the "no-rise" and "no adverse effect" requirements. A list of potential compensatory actions has been included in FEMA's "Procedures For Compliance With Floodway Regulations," dated May 1990. Copies of this document can be obtained from this office. Any proposed compensatory actions involving the alteration of the stream channel or within 50-feet of the stream banks should be reviewed by the appropriate DEC Regional Permit Administrator for compliance with 6 NYCRR Part 608, Use and Protection of Waters.

NYSDEC Hydraulic Model Download Application

The NYSDEC Hydraulic Model Download Application allows users to download available hydraulic models for stream segments in New York State. Click on a stream segment to view reach specific information and download the applicable model. There may be models within the downloaded materials that cover additional stream segments. Folders in the downloaded file have descriptive names and notes to assist the user in determining the applicable model to use. Refer to the map legend to identify if the hydraulic model is currently available for the stream segment of interest. This website is currently under development. Contact [email protected] with any questions about this application.

The Application can be found at the following link: Hydraulic Model Download App (arcgis.com)

Hydraulic Model Download Tool Map

The models available are electronic copies of the input files used to calculate the floodplain limits and water surface profiles. The State of New York, the New York State Department of Environmental Conservation (“Department”), and the Department’s officers and employees do not guarantee these models to be the legal models for FEMA purposes or any other purpose. It is the user's responsibility to confirm that these models are the effective models for the Flood Insurance Studies in question. Dates of models listed and model extents shown are not guaranteed by the State of New York, the Department, or the Department’s officers and employees to be accurate. Additional models not listed may be available. 

The data and information on this website are subject to change. All models are provided "as is" without any kind of warranty or guarantee as to their accuracy or applicability for any particular purpose. The user and third parties assume all risks concerning the suitability and accuracy of the models. These models may contain technical inaccuracies, typographical errors, and/or other errors. The State of New York, the Department, and the Department’s officers and employees assume no responsibility for and disclaim all liability for any inaccuracies and errors in the models.

The State of New York, the New York State Department of Environmental Conservation (“Department”), and the Department’s officers and employees make no representations or warranties as to any content on this website, and do not warrant that the functions, information, links or content will meet your requirements, or that they are fit for any purpose, legal or otherwise, or that the content will be error free, or that defects will be corrected. Under no circumstance, including but not limited to negligence, will the State of New York, the Department, or any of the Department’s officers or employees be liable to you or any third party for any direct, indirect, special, or incidental or consequential damages or expenses whatsoever, including attorney fees that result from the use of, or inability to use, the information on this website.   

The modeling and associated data available on this website are, to the best of the Department’s knowledge, electronic copies of the input files to various modeling programs used to calculate the floodplain and floodway limits and water surface profiles for the respective Flood Insurance Studies.  However, the State of New York, the Department, and the Department’s officers and employees do not warrant or guarantee these models to be the legal models for FEMA purposes (or any other purpose).  It is the user's responsibility to confirm that these models are the effective models for the Flood Insurance Study in question. Please refer to the FEMA website for information on how to obtain copies of this modeling. Dates of models listed and model extents shown are not guaranteed to be accurate. The user must verify the model information. All models available may also not be listed; the user should not assume that if a model is not shown, that it does not exist. 

All models are provided "as is" without any kind of warranty or guarantee as to their accuracy, fitness, or applicability for a particular purpose. Even though every effort is made to provide accurate information, the user and third parties assume all risks concerning the suitability and accuracy of the model viewed or downloaded from this website. These models may contain technical inaccuracies or typographical errors. The State of New York, the Department, and the Department’s officers and employees assume no responsibility for and disclaim all liability for any such errors in the models. 

The Department may make changes to these models at any time and without notice. The Department strives to have this modeling resource as complete and accurate as possible; any possible errors found in these models can be reported to the Department by emailing the Floodplain Program. The Department staff can only provide limited assistance in interpretation or guidance regarding these models, and assume no responsibility for any such assistance. For more information on the modeling process, you may consult the Floodplain program Floodplain Development and Floodway Guidance (“Guidance”), however that Guidance also is not guaranteed to be accurate or suitable for any particular purpose, and the State of New York, the Department, and the Department’s officers and employees assume no responsibility with respect to that Guidance.

By using this website, the user and third parties waive the right to bring any claim, cause of action, or suit whatsoever against the State of New York, the Department, and the Department’s officers and employees that arises out of, or relates to, this website, or information referenced in this website, to the fullest extent allowed by law. Furthermore, the user and third parties agree to indemnify and hold harmless the State of New York, the Department, and the Department’s officers and employees for any and all claims, causes of action, and suits whatsoever that arise out of, or relate to, this website and/or the information referenced in this website. However, to the extent that any claim, cause of action, or suit may be determined, these terms and conditions and any claim, cause of action, or suit arising out of, or relating to, this website and/or any associated information, shall be governed by the Laws of the State of New York. Any claim, cause of action, or suit arising from, or relating to, this website, associated information, or these terms and conditions, shall be determined by a New York court of competent jurisdiction. In the event that any of these terms and conditions are determined by a court of competent jurisdiction to be invalid or unenforceable, the remaining terms and conditions shall remain in full force and effect.

By accessing this website, you agree to the General Disclaimer & Terms and Conditions.

Floodplain Construction Requirements in New York State

When Floods Occur

Floods occur when runoff from rain or snowmelt exceeds the capacity of rivers, stream channels or lakes and overflows onto adjacent land. Floods can also be caused by storm surges and waves that inundate areas along tidal or Great Lakes coastlines. Throughout history, floods have claimed uncounted human lives and devastated property, even destroying cities. Yet people continue to settle and build in floodplains, increasing the risk of property damage and loss of life.

What is a floodplain?

Floodplains are low-lying lands next to rivers and streams. When left in a natural state, floodplain systems store and dissipate floods without adverse impacts on humans, buildings, roads and other infrastructure. Natural floodplains add to our quality of life by providing open space, habitat for wildlife, fertile land for agriculture, and opportunities for fishing, hiking and biking.

Floodplains can be viewed as a type of natural infrastructure that can provide a safety zone between people and the damaging waters of a flood. But more and more buildings, roads, and parking lots are being built where forests and meadows used to be, which decreases the land's natural ability to store and absorb water. Coupled with changing weather patterns, this construction can make floods more severe and increase everyone's chance of being flooded.

The National Flood Insurance Program

The National Flood Insurance Program is a federal program created in 1968 to provide flood insurance to people who live in areas with the greatest risk of flooding, called Special Flood Hazard Areas. The program provides an alternative to disaster assistance and reduces the escalating costs of repairing damage to buildings and their contents caused by floods. The program provides flood insurance, while at the same time encouraging the sensible management and use of floodplains to reduce flood damage.

The National Flood Insurance Program offers flood insurance to homeowners, renters and business owners, provided their communities use the program's strategies for reducing flood risk, including adopting and enforcing floodplain management ordinances to reduce future flood damage. Community participation in the National Flood Insurance Program is voluntary. However, flood insurance and many kinds of federal disaster assistance are not available in communities that do not participate in the program. Fortunately, in New York, 1,466 communities participate in the National Flood Insurance Program.

Each participating community has a local law for flood damage prevention that contains specific standards for any development in federally mapped Special Flood Hazard Areas. These areas have a one percent or greater chance of experiencing a flood in any year and are shown on Flood Insurance Rate Maps provided by the Federal Emergency Management Agency (FEMA).

The New York State Department of Environmental Conservation (DEC) is the state's National Flood Insurance Program coordinating agency. Local officials, developers, and the public may contact the DEC for technical assistance and guidance in all matters associated with the National Flood Insurance Program.

Find the National Flood Insurance Application here.

Questions about Flood Insurance in NYS?

Find frequently asked questions about flood insurance in NYS.

Learn More

Construction Regulations

All communities that participate in the National Flood Insurance Program have a local law or ordinance that regulates development within mapped floodplains. The basic standards are contained below. However, anybody who wishes to develop any area within a floodplain should consult with their local floodplain manager, often a building inspector or zoning officer, for specific requirements.

All development, including buildings and other structures, mining, dredging, filling, paving, excavation, drilling, or storage of equipment or materials is subject to construction regulations if it occurs within a Special Flood Hazard Area. The Special Flood Hazard Area is the area that would be inundated by the100-year flood, better thought of as an area that has a one percent or greater chance of experiencing a flood in any single year. Special Flood Hazard Areas are shown on federal flood maps, known as Flood Insurance Rate Maps, as shaded areas labeled with the letter "A" or "V" sometimes followed by a number or letter.

  • "V" zones are coastal flood hazard zones subject to wave run-up in addition to storm surge.
  • "A" zones include all other special flood hazard areas.
  • "VE" zones, "AE" zones, "V" zones, or "A" zones followed by a number are areas with specific flood elevations, known as Base Flood Elevations.
  • A zone with the letter "A" or "V" by itself is an approximately studied flood hazard area without a specific flood elevation.
  • Within an "AE" zone or a numbered "A" zone, there may be an area known as the "regulatory floodway," which is the channel of a river and adjacent land areas which must be reserved to discharge the 100-year flood without causing a rise in flood elevations.

The floodway is shown either on the community's Flood Insurance Rate Map or on a separate "Flood Boundary and Floodway" map for maps published before about 1988. Within regulatory floodways, more stringent development controls exist than elsewhere in the Special Flood Hazard Area.

In New York State, local communities that participate in the National Flood Insurance Program regulate development in Special Flood Hazard Areas. An exception is development funded and undertaken by the State or Federal government, which is regulated by the responsible agency, subject to technical assistance by the New York State Department of Environmental Conservation and the Federal Emergency Management Agency. Nearly all New York communities participate in the National Flood Insurance Program. Each participating community in the state has a designated floodplain administrator. This is usually the building inspector or code enforcement official. Local communities are encouraged to provide an extra margin of safety by requiring structures to be elevated above the base flood elevation. Always check with your local community to find out what their standards are.

Private development is subject to local floodplain development permits. In addition, New York State Environmental Conservation Law states that local laws or ordinances passed to qualify for participation in the National Flood Insurance Program shall apply to any development undertaken within the community by any county, city, town, village, school district or public improvement district.

Any new structure or structure that is substantially improved or substantially damaged by any cause is subject to floodplain development regulations. Substantial improvement or damage occurs when the improvement or the value of the damage exceeds 50% of the market value of the structure.

New construction and substantial improvement or substantially damaged structures must be elevated on pilings, columns or sheer walls such that the bottom of the lowest horizontal structural member supporting the lowest elevated floor is elevated to or above the base flood elevation (plus two feet beginning in 2007). Detailed standards exist regarding how to elevate the structure.

When there is a base flood elevation available, the lowest floor including any basement, must be at or above the base flood elevation (plus two feet beginning in 2007). Elevation may be by means of properly compacted fill, a solid slab foundation, or a "crawl space" foundation which contains permanent openings to let flood waters in and out. Non-residential structures may be flood proofed in lieu of elevation.

No development is allowed within a regulatory floodway unless the developer has first proven that the development will not increase flood elevations at any location during the 100-year flood. For more information please see our Floodplain Development and Floodway Guidance webpage.

The base flood elevation (BFE) is the elevation that the one hundred-year flood, better thought of as the flood that has a one percent or greater chance of occurring in any given year, rises to. It is the basic standard for floodplain development, used to determine the required elevation of the lowest floor of any new or substantially improved structure. As of May 2020, the new requirement as stated in R322.1.4.1. Determination of Design Flood Elevations requires a BFE be obtained from a local, federal, or state source, or the applicant can have a BFE established by a licensed P.E. The use of historical flood data may be used if it is well documented.

Note: Machinery and equipment servicing a building must be elevated to or above the base flood elevation.

Building Elevation and Flood Insurance

Flood insurance for a house built two or more feet above the base flood elevation will cost about half as much as for a house built to the base flood elevation. Flood insurance for a house built just one foot below the base flood elevation will cost about four times more than for a house built to the base flood elevation. This additional cost could mean tens of thousands of dollars over the life of a 30-year mortgage. Get more information about flood insurance.Floodplain Management Training Resources

DEC offers professional development workshops and trainings for local floodplain administrators across the state. These trainings provide county and municipal officials the background to properly enforce their local floodplain management ordinances. In addition to DEC-sponsored trainings, there are several other state or federally sponsored training opportunities available.

Floodplain Management Training Resources

DEC encourages community officials interested in learning more about the National Flood Insurance Program (NFIP) and their role in administering the program to participate in the training opportunities below.

Upcoming Training Events

There are no training events planned at this time.

Independent Study Training for Floodplain Administrators (Non-Residential)

An online study guide and four tutorials available through FEMA's website include:

FEMA National Flood Insurance Program (NFIP) Floodplain Management Requirements: A Study Guide and Desk Reference for Local Officials
  • The NFIP Floodplain Management Requirements Study Guide and Desk Reference can enhance the knowledge and skills of local officials responsible for administering and enforcing local floodplain management regulations, as well as function as a study guide to help them study for the exam for the Association of State Floodplain Manager's (ASFPM) Certified Floodplain Manager designation.
Introductory Tutorials
  • How to Read a Flood Insurance Rate Map Tutorial:
    This tutorial educates users on the use and application of the Flood Insurance Rate Maps (FIRMs) produced by the Federal Emergency Management Agency (FEMA). Each component of the FIRM is explored. The tutorial includes a section that contains examples of how to get specific information from FIRMs.
  • How to Read a Flood Insurance Study Tutorial:
    This tutorial educates users on the use and application of the Flood Insurance Study (FIS) reports produced by the Federal Emergency Management Agency (FEMA). Each component of the FIS report--including Flood Profiles, cross sections, and notes-- is explored and explained.
  • Letter of Map Change (LOMC) Tutorial for Amendments: The online LOMC is an easy way to request a Letter Of Map Amendment (LOMA) from FEMA. All the information and supporting documentation can be submitted and the status of your LOMA can be checked. The PowerPoint presentation, provides information about LOMCs including a how to guide of the amendment process.
  • Letter of Map Amendment (LOMA)/Letter of Map Revision - Fill (LOMR-F) Tutorial
    The tutorials include how and what to submit for a LOMA using the MT-EZ form and how and what to submit for a LOMR based on fill using the MT-1 form. These forms and information are necessary to request removal of one or more properties and/or structures from a Special Flood Hazard Area (SFHA).

NYS After-the-Flood Quick Guide

Recovering from a flood is a challenging process for many property owners in New York State. Taking the right steps and knowing important contact information can make recovery easier and reduce the chances of flood damages occurring in the future. This After-the-Flood Quick Guide is a tool to help NYS residents navigate recovery from flooding and access essential resources following a flood event:

  • Step One – Returning Home After the Flood. Tips on clean up, debris removal, and getting help.

  • Step Two – Now What? Guidance on floodplain rules, permit requirements, and starting repairs.

  • Step Three – Make Sure it Doesn’t Happen Again. How to protect your building from future flooding, who to contact, and programs to help pay for it. 

This guide was developed and funded jointly by the New York State Department of Environmental Conservation (NYSDEC) and the Federal Emergency Management Agency (FEMA).

NYS Floodplain Management Quick Guide

The NYS Floodplain Management Quick Guide provides community officials with essential information about floodplain development standards and floodplain permitting requirements as well as technical resources available to community officials, developers, and residents. This guide incorporates federal requirements based on the National Flood Insurance Program (NFIP) in addition to New York State-specific standards and program information. Floodplain administrators across the state can use this resource as a reference during the implementation of the NFIP within their community.

This Quick Guide was developed and funded jointly by the New York State Department of Environmental Conservation (NYSDEC) and the Federal Emergency Management Agency (FEMA).

Community Rating System (CRS) Training

The CRS Program is a voluntary incentive program that recognizes and encourages community floodplain management practices that exceed the minimum requirements of the National Flood Insurance Program. In CRS communities, flood insurance premium rates are discounted to reflect the reduced flood risk resulting from the community's efforts that address the three goals of the program:

  1. Reduce and avoid flood damage to insurable property
  2. Strengthen and support the insurance aspects of the National Flood Insurance Program
  3. Foster comprehensive floodplain management

The CRS Webinar Series will be providing live and on-demand training to communities that are not yet participating in the CRS Program, local government staff who are new to the CRS, and those with experience in the program. For registration information and further details, please see the CRS Resources webpage.

Recommended Training for Floodplain Management Administrators (Residential)

Residential courses are offered through FEMA's Emergency Management Institute (EMI) at the National Emergency Training Center in Maryland. These courses are designed for Local, State, and Federal officials who administer the National Flood Insurance Program. Recommended Residential Training Courses offered through FEMA EMI include the following:

E0273 focuses on the National Flood Insurance Program and concepts of floodplain management, maps and studies, ordinance administration, and the relationship between floodplain management and flood insurance This course provides a comprehensive overview to the NFIP and is designed for officials with limited floodplain management experience.

This advanced floodplain management course provides a dynamic and interactive instruction that covers the following four topics in detail:

  • Local Floodplain Manager Roles and Responsibilities (1 day)
  • National Flood Insurance Program Floodplain Rules and Regulations in Depth (1 day)
  • Letter of Map Change Procedures for Applying and Floodplain Management Implications (1 day)
  • Preparing for Post-Disaster Responsibilities (1 day)

This advanced floodplain management course is a dynamic and interactive instruction that covers the following four topics in detail:

  • Placement of Manufactured Homes and Recreational Vehicles in the Floodplain (1 day)
  • National Flood Insurance Program Flood Insurance Principles for the Floodplain Manager (1 day)
  • Higher Standards in Floodplain Management (1 day)
  • Hydrology and Hydraulics for the Floodplain Manager (1 day)

This advanced floodplain management course is a dynamic and interactive instruction that covers the following five topics in detail:

  • Floodway Standards (1 day)
  • Disconnects between National Flood Insurance Program Regulations and Insurance (1 day)
  • Common Noncompliance Issues (1/2 day)
  • Digital Flood Insurance Rate Maps (DFIRMs) (1/2 day) Substantial Improvement/Substantial Damage (1 day)

E0278 covers the Community Rating System (CRS), a nationwide initiative of FEMA's NFIP. It describes activities eligible for credit under the 2017 CRS Coordinator's Manual, how a community applies, and how a community modifies an application to improve its classification.

E0297 provides engineering and economic guidance to architects, engineers, and local code enforcement officials in retrofitting existing 1- to 4-family residential structures situated in flood-prone areas. The retrofitting measures presented are creative, practical, compliant with applicable floodplain regulations and satisfactory to most homeowners.

Additional Information and Resources

NYS Office of Emergency Management Hazard Mitigation Program
FEMA Coastal Analysis and Mapping
Federal Emergency Management Agency
FEMA Forms
National Flood Insurance Program
NYS Floodplain and Stormwater Managers Association
FEMA Map Service
Association of State Floodplain Managers
ASFM - No Adverse Impact Toolkit
Contact for this Page

DOW, Bureau of Flood Protection
625 Broadway
Albany, NY 12233

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