The GNWT is developing new flood maps for NWT communities at highest risk of riverine flooding. This work is supported thanks to financial and technical assistance from Government of Canada through the Flood Hazard Identification and Mapping Program (FHIMP), until March 2028.

Many NWT communities currently depend on flood maps produced in the 1980s under the former federal Flood Damage Reduction Program. Using improved tools, technology and data, as well as local knowledge, the GNWT’s Department of Environment and Climate Change and the Department of Finance’s NWT Centre for Geomatics are developing more accurate, up-to-date flood maps. This work is focused on riverine communities at highest risk of flooding and is carried out with community and Indigenous governments and engineering consultants.

For flood mapping information for the NWT’s coastal communities please contact the Department of Municipal and Community Affairs’ Beaufort Delta Region office at (867)-678-8045.

Flooding in the NWT

Flooding is one of the NWT’s most severe natural hazards, as identified in the 2024 NWT Hazard Identification Risk Assessment. Recent flood events have caused major damage and required multiple community evacuations.

Residents can find flood preparedness information on the GNWT’s Be Ready for Floods page.

ECC provides current water level and climate information through monthly Water Monitoring Bulletins and an annual Spring Outlook Bulletin. During spring breakup, ECC publishes more frequent bulletins to update communities on potential ice jam or high-water conditions. To receive bulletins by email, contact nwtwaters@gov.nt.ca.

Types of flooding

There are different types of flooding affecting communities in the NWT. The most common is riverine (fluvial) flooding.

Riverine (fluvial) flooding – Occurs when water flows outside of a river, stream, or creek channel and onto normally dry land. Causes may include ice jams, heavy rainfall and snowmelt.

Riverine flooding is either ice-affected or open water:

• Ice-affected flooding – Occurs when river ice changes the flow of water, causing water levels to rise. This is often, but not always, caused by an ice jam. The risk is highest during spring breakup.
• Open water flooding – Occurs due to high streamflow not changed by river ice. It may be caused by heavy rain or snowmelt which could happen some distance away from the location of flooding.

NWT Communities at Highest Risk of Riverine Flooding

The NWT communities at highest risk of riverine flooding are:

• Aklavik
• Fort Good Hope
• Fort Liard
• Fort McPherson
• Fort Simpson
• Hay River
• Kátł’odeeche First Nation
• Jean Marie River
• Nahanni Butte
• Tulita

Flood Maps and Community Planning

Flood maps are important tools for community planning and government decision-making. They can be used by communities, governments and residents to support community land use planning, guide flood mitigation activities, prepare for emergencies, improve public safety, and increase public awareness about flood risk.  

The Department of Municipal and Community Affairs’ Planning in Flood Hazard Areas Guide provides guidance to community governments, and planners, engineers and other qualified professionals they retain, on the integration of flood hazard mapping into community planning and land management decisions. This guide was developed under the NWT Community Planning Framework.

Engaging Community and Indigenous Governments on Flood Map Development

As flood mapping projects advance, ECC Water Monitoring and Stewardship Division staff meet with community and Indigenous governments to discuss the mapping approach, historical and technical information needed for mapping, and key steps in the process.  This may include targeted engagement sessions, meeting with leadership and staff, and public open houses. In some communities, Indigenous guardians and local staff support field activities and collection of historical flood information.

Understanding Flood Mapping

Flood mapping includes a number of technical terms. A list of flood mapping definitions adopted by the GNWT is available here (INSERT PDF OF TECHNICAL DEFINITIONS). 

There are two types of flood maps being developed in the NWT – flood hazard maps and flood inundation maps.

Flood Inundation Map

• A map that shows where water went during a past flood. Most inundation maps in the NWT show the highest flood on record.
• Some flood inundation maps can show where water would go in a potential future flood.
• Flood inundation maps are usually created using high-water marks, satellite imagery, aerial photos, community observations, or engineering studies of how water moves.
• These maps do not show the depth of flooding. The depth could be very shallow to several feet deep.
• These maps are not a perfect representation of flood inundation, but they provide the best possible depiction based on the available data and information.
• Flood inundation maps are intended for community emergency planning.

Flood Hazard Map

• A map that shows the area that would be covered by water during a flood with a specific chance of happening any given year. This chance is called the annual exceedance probability (AEP).
• These maps are usually created through detailed engineering studies and may rely on some of the same information used to make flood inundation maps.
• This is a detailed and technical map that must be authenticated (stamped) by a qualified professional, such as a Professional Engineer.
• Flood hazard maps are intended for community land use planning and flood mitigation planning.

Flood Hazard Area

• This is the entire area at risk of flooding shown on a flood hazard map. This area is usually divided into two parts – the floodway and the flood fringe. The definitions differ depending on whether the flood is ice-affected or open water.
  • Floodway – includes the river and any parts of the flooded area where the water is deepest, fastest and most destructive, or where moving ice is present during ice-affected floods. This is the area where flood waters and/or ice pose the greatest risk to people, property and infrastructure.
  • Flood fringe – includes parts of the flooded area where water is shallower, slower and less destructive, and where there is no moving ice during ice-affected floods. Flood impacts in this area are generally less severe than within the floodway.

In the NWT, flood hazard maps are being developed for the following:

• 100-year flood (1% AEP): a flood with a 1% chance of occurring or being exceeded in any given year
• 200-year flood (0.5% AEP): a flood with a 0.5% chance of occurring or being exceeded in any given year

Annual Exceedance Probability (AEP)

• The AEP is the chance that a flood of a certain size will happen in any given year. For example, a flood with a 1% chance of occurring in any given year is called a 1% AEP flood, which is the same as a 100-year flood. This does not mean that a flood that size happens only once every 100 years – it could occur more or less often. A 1% AEP (or 100-year flood) is more likely to occur in any given year than a 0.5% AEP (or 200-year flood). A 200-year flood has the potential to be more damaging than a 100-year flood.

Flood Hazard Maps and Climate Change

Climate change is considered in the flood mapping process, and, where possible, flood maps are informed by future predicted climatic conditions.

Flood Maps

The following communities have new flood maps completed under the Flood Hazard Identification and Mapping Program (FHIMP). Final reports are also available for each flood map project.

Aklavik (mapping completed 2025):

• Aklavik 2006 Flood Inundation Map
• Aklavik 200-year Ice Jam Flood Hazard Map
• Aklavik 100-year Ice Jam Flood Hazard Map
• Aklavik Flood Hazard Mapping Study

Fort Simpson (mapping completed 2025):

• Fort Simpson (Łı́ı́dlı̨ı̨ Kų́ę́) 2021 Flood Inundation Map
• Fort Simpson (Łı́ı́dlı̨ı̨ Kų́ę́) 200-year Ice Jam Flood Hazard Map
• Fort Simpson (Łı́ı́dlı̨ı̨ Kų́ę́) 100-year Ice Jam Flood Hazard Map
• Fort Simpson (Łı́ı́dlı̨ı̨ Kų́ę́) Flood Hazard Index Map
• Fort Simpson Flood Hazard Mapping Study – Summary report

Hay River and Kátł’odeeche First Nation (mapping completed 2025):

• Hay River (Kátł’odeh) 2022 Flood Inundation Map
• Hay River (Kátł’odeh) 200-year Ice Jam Flood Hazard Map
• Hay River (Kátł’odeh) 100-year Ice Jam Flood Hazard Map
• Hay River (Kátł’odeh) 100-year Open Water Flood Hazard Map
• Hay River (Kátł’odeh) Flood Hazard Index Map
• Hay River (Kátł’odeh) Flood Hazard Mapping Study – Summary report

Nahanni Butte (mapping completed 2025):

• Nahanni Butte (Tthenáágó) 2012 Flood Inundation Map
• Nahanni Butte (Tthenáágó) 200-year Open Water Flood Hazard Map
• Nahanni Butte (Tthenáágó) 100-year Open Water Flood Hazard Map
• Nahanni Butte (Tthenáágó) 200-year Open Water Flood Hazard Map – Climate Change Scenario SSP2-4.5
• Nahanni Butte (Tthenáágó) 200-year Open Water Flood Hazard Map – Climate Change Scenario SSP5-8.5
• Nahanni Butte Flood Hazard Mapping – Final report

As flood maps are finalized for remaining communities, they will be added to this site.

New 200-year flood hazard data will replace the 1980s flood data where updates have been made on the GNWT Administration of the Territorial Lands Act System (ATLAS).  This data will also be available to GIS professionals as a Web Map Service.

Other Flood Map Related Products

NWT Ice Jam Flood Mapping Guidelines V1.0: This document outlines best practices for preparing flood hazard maps in regions where ice jam flooding is the primary driver of flood risk. Created by ECC, in collaboration with Natural Resources Canada through the Flood Hazard Identification and Mapping Program, these evergreen guidelines help address a gap in national standards for ice-jam flood mapping and are intended to complement the Federal Flood Mapping Guideline Series.

ECC and the NWT Centre for Geomatics conduct additional research and modelling to support flood understanding and resilience in the NWT.

New tools and products informed by research and modelling will be added to this page as they are completed.

ECC would like to acknowledge the continued financial and technical support of Natural Resources Canada through the FHIMP. Technical support is also provided by Environment and Climate Change Canada. Additional financial contributions from Crown Indigenous Relations and Northern Affairs Canada’s Climate Change Preparedness in the North program has supported NWT flood mapping and related products.