Flood Information

Several Denver neighborhoods experience flooding during rainstorms or after very wet winters when the ground is saturated. More extreme flooding is also possible in lower-lying areas of town, and some residents are at increased risk of flooding because of their proximity to a major waterway.  

The city encourages all residents to be aware of flood risks and take precautions to protect their lives and property.  Please use the resources below to understand your flood risk and get information on what you need to do to stay safe.

Did You Receive a Flood Risk Letter from the City?

Rainstorm Safety Tips

Please be safe on Denver’s streets and urban trails this season!

Rainstorms in Denver are common throughout the spring and summer months. It's important to remember that floods caused by rain can occur anywhere, with floodwaters rising gradually or flash floods striking suddenly. Water's powerful force can easily overtake vehicles and people.


Safety Tips For Driving in Heavy Rain

  • If you must drive in the rain, drive slowly and steadily.
  • DO NOT DRIVE THROUGH FLOODWATERS!
  • Six inches of water will reach the bottom of most passenger cars, causing loss of control or possible stalling.
  • One foot of water will float most vehicles.
  • Two feet of rushing water can sweep away most vehicles — including SUVs and pick-ups.
  • Stay away from water that downed electrical or power lines have fallen into; the electric current passes through water easily.
  • Stay off the telephone unless you must report severe injuries or call for help.

Safety Tips For Walking or Cycling on Urban Trails

When rain is falling, it’s best not to walk or bike near a river or stream, even on Denver’s paved urban bike and walking trails; water flow can quickly increase and flooding can occur without notice.

Move to higher ground and never go into a culvert! If you are on a streamside trail during a rainstorm use the alternate trail up to street level to avoid underpasses and culverts.

  • NEVER take shelter in a culvert, under a bridge, or in an enclosed space, especially in low elevations by rivers and streams. Always go to higher ground out of the flow of water.
  • Do not walk or bike through moving water. Six inches of moving water can cause a person to fall.
  • If lightning is present, do not stand under or near an isolated tree or group of trees.
  • Never allow children to play around streams, drainage ditches or viaducts, storm drains or flooded areas

Localized Street Flooding 

In some areas that are geographical low-points and underpasses, water can't be expected to disappear down the storm inlets instantly — the pace and volume of the rainfall is too quick and too great to immediately drain off. It takes time for the system to accommodate it.

If you know that your street tends to flood because it is located in a low point, be sure to move your vehicles to higher ground.

Neighborhood Prevention Tips

What you can do to prevent flooding and keep your neighborhood clean, too

  • Ensure street gutters and alleys are clear of trash and loose items that could potentially interfere with storm drainage.
  • Avoid placing trash and recyclables in bags or containers directly on drains and inlets.
  • Avoid placing your trash or recycling carts, trash bags, trash cans or loose items out early on your collection day, especially on days when rain is in the forecast. City rules prohibit trash or recyclables from being placed out for collection earlier than 7 p.m. on the day prior to collection and requires that emptied containers be removed from the collection location by 7 p.m. the day of collection.
  • When heavy rain is forecast, place trash and recycling bins and items at the end of your driveway close to, but not in, the street to keep the gutter flow line clear and to avoid spillage due to heavy water flow.
  • Do not rake leaves, grass clippings or yard debris into the street or alley or put them down an inlet.
  • Never, ever throw lawn clippings and other yard debris into a gulch or stream. Call the Wastewater Management Division (303-446-3400) if you see dumping or debris in a drainage way.

Downed Power Lines/Cables

Stay clear of downed lines and report them immediately to Xcel Energy at 1-800-895-1999. If a power line has fallen onto a vehicle, stay away from the vehicle. Seek help immediately by calling 911.


Natural Gas Line Damage

Natural gas service lines are buried throughout the city, and they can sustain damage in times of heavy rain and flooding. If you smell natural gas (the odor is similar to sulfur or rotten eggs), it may indicate a gas leak. Immediately leave your home or outside area with gas odor. Once safely outside or away from the area with the odor, call Xcel Energy at 1-800-895-2999 to report your concern. Avoid using anything that has the potential to create a spark. Do not smoke, turn on or off lights, turn on appliances, use garage door openers, start a car, or use phones in an area where gas may be present.


Storm and Tree Damage Information

Property owners are responsible for cleanup of debris from trees on private property and from trees within the public right-of-way adjacent to their property. (For residents on a designated parkway, the adjacent property owners are not responsible for public right-of-way trees on the parkway but would need to address trees on other streets if they live on a corner or have an alley.)

Limbs on the ground are considered debris. Property owners can hire any licensed company to haul limbs away — for this type of work, the company does NOT have to be a licensed tree contractor.

When a tree or limb is blocking safe access to the street or right-of-way, Denver Forestry has an on-call contractor remove the limb or tree and bills the property owner for the work.

See guidelines for tree damage, emergency tree and limb removal, and lists of licensed and insured tree care contractors at www.denvergov.org/forestry

For smaller broken branches and yard debris, see disposal and recycling options from Solid Waste Management

To report significant flooding issues in Denver, please call 311

 


What Is My Flood Risk?

Check The Flood Maps

Denver Regulatory Floodplain

Denver Potential Inundation Area (PIA) - NEW!


Mile High Flood District (MHFD) Flood Hazard Area Delineation (FHAD)

FEMA Flood Insurance Rate Maps (FIRMs)


Terms & Definitions

Flood or Flooding: A general and temporary condition of partial or complete inundation of normally dry land.

Floodplain: Any land area susceptible to being inundated as the result of a flood.

Base Flood: Also known as “100-year flood” or "1% annual chance flood” — A flood having a one-percent chance of being equaled or exceeded in any given year. The term does not imply that the flood will necessarily happen once every one hundred years.

Special Flood Hazard Area (SFHA): The land within a community subject to inundation by the base flood as shown on the FEMA Flood Insurance Rate Map (FIRM).

Flood Insurance Rate Map (FIRM): The official map on which FEMA has delineated both the SFHA and the risk premium zones applicable to the community.

Regulatory floodplain: The area of land subject to inundation by the base flood as delineated by the SFHA and any other floodplain maps that have been adopted by the City & County of Denver. These areas are regulated in accordance with the City & County of Denver Floodplain Ordinance.

Potential Inundation Area (PIA): Areas where stormwater has been reported to collect in depths exceeding 12" during storm events and where various studies have identified the potential for flooding in a major storm event. The areas depicted represent current best-available information of these hazards. PIAs are not to be confused with SFHAs. 

Other Common Flood Terms and Definitions(PDF, 422KB) 

Flood Insurance: Information For Property Owners and Renters

Flood Insurance

Flood insurance is required by law for any primary building with federally backed funding (e.g., mortgage or business loan) in a flood map zone with an A designation — A, AE, AH, AO, AR, and A99. In Zone X and Zone D, flood insurance is optional

The City and County of Denver recommends that property owners (and renters) consider flood insurance even when it not required, especially in areas that are prone to flooding.

Talk to an insurance agent who has experience with flood policies, and check out the National Flood Insurance Program (NFIP) website at FloodSmart.gov. For other flood insurance questions, call the FEMA Flood Insurance Hotline at 1-800-621-FEMA. After selecting the preferred language, select Option 2 for Flood Insurance.


Basic Flood Information Facts

  • Flood insurance is available regardless of whether or not the building is in a Special Flood Hazard Area (SFHA).
  • Areas outside of SFHA may be eligible for low-cost preferred risk policy (PRP).
  • Standard homeowners’ insurance policies do not cover flood losses.
  • Property owners can insure building only or building and contents.  Renters can insure just their contents, even if owner does not insure the structure.
  • There is a 30-day waiting period for flood insurance policies to go into effect; don’t wait until rainy season to get a policy.
  • Flood insurance has limited coverage in basements; talk to your insurance agent about policy details, including exclusions/restrictions.

The City and County of Denver participates in the NFIP Community Rating System (CRS) program which rewards our stormwater and floodplain management efforts by offering flood insurance discounts to certain policyholders. The City and County of Denver is currently a CRS Class 7 (15% discount) effective May 1, 2017. (Previously it was CRS Class 8, 10% discount.) CRS discounts are available to policyholders located in a SFHA. Preferred Risk Policies (PRP) do not receive a CRS discount because these are already low cost policies.


NFIP Policyholder Information

NFIP Policyholder Letters

Beginning in 2017, policyholders will receive annual letters from the Federal Emergency Management Agency as notification that a review of their property's flood risk has been done.

FEMA Letters: Flood Risk and Policy Options


Special Flood Hazard Area Zones

Zone A
Subject to 1% annual chance flooding. No base flood elevations determined.

Zone AE
Subject to 1% annual chance flooding. Base flood elevations determined.

Zone AE Floodway (cross hatched)
The floodway is the channel of a stream plus any adjacent floodplain areas that must be kept free of encroachment so that the 1% annual chance flood can be carried without substantial increases in flood heights.

Zone AH
Subject to 1% annual chance flooding. Base flood elevations determined. Flood depths of 1 to 3 feet usually in areas of ponding.

Zone AO
Subject to 1% annual chance flooding.  Base flood elevations determined.  Flood depths of 1 to 3 feet usually sheet flow on sloping terrain.

Zone AR
This is an area that was formerly protected from the 1% annual chance flood event by a flood control system that was subsequently decertified, and is currently in the process of being restored to provide protection from the 1% annual chance or greater flood event.

Zone A99
This is an area to be protected from the 1% annual chance flood event by a Federal flood protection system under construction; no base flood elevations determined.


Other Flood Areas

Shaded Zone X
Areas of 0.2% annual chance flood; areas of 1% annual chance flood with average depths of less than 1 foot or with drainage areas less than 1 square mile; and areas protected by levees from a 1% annual chance flood.

Unshaded Zone X
Areas determined to be outside the 0.2% annual chance floodplain.

Zone D
Areas in which flood hazards are undetermined, but possible.

Flood Map Changes in Denver: Are You Affected?

Flood Map Updates

Flood risk changes over time due to natural and man-made changes. The corresponding flood maps are revised periodically to reflect these changes and to improve map accuracy using better data and technology. The City and County of Denver works with MHFD and FEMA to study flood risk and update flood maps.

Major Flood Map Revisions ("Physical Map Revision" or PMR)

A PMR is a FEMA process that is used for large changes to the Flood Insurance Rate Map (FIRM) and are commonly used to incorporate MHFD Flood Hazard Area Delineation (FHAD) studies into the FEMA FIRMs.

Minor Flood Map Revisions (called "Letter of Map Change" or LOMC)

  • A FEMA Letter of Map Revision (LOMR) is used to update flood maps to reflect changes as a result of a construction project.
  • A FEMA Letter of Map Amendment (LOMA) can be used to remove a building or property from the SFHA when inadvertently mapped in the SFHA. A successful LOMA can help reduce or eliminate flood insurance premiums. This typically requires the services of a Professional Land Surveyor and may require an elevation certificate. If you think you may be inadvertently mapped in the SFHA, please contact the City & County of Denver's Floodplain Management Group at floodplain@denvergov.org or 720-865-3215 for guidance.

If you live in an area that is under revision

  • Property owners will be notified by MHFD of any FIRM revisions — whether you are at increased risk or have been added to the SFHA, or if you are at reduced risk or removed from the SFHA
  • You are not required to do anything until you are officially notified of a change in the FIRM. However, it is recommended that all flood risk information be considered for emergency planning, mitigation, flood insurance, and development/redevelopment purposes. Carefully consider the impacts of a future FIRM change, especially when developing or redeveloping a property. It is not advised to develop/redevelop in a manner that increases flood risk and thus may impact future flood insurance rates.
  • Consider purchasing flood insurance, even if it is not currently required; there may be benefits for current policyholders if your property's flood risk changes. 
  • If you have questions about buying or selling your property during the study period, please consult with your real estate agent.

Resources for Homeowners and Business Owners

Drainage Complaints or Maintenance Requests

In Denver, contact 311 or use Pocketgov

For properties in the floodplain

Construction & Remodeling

In general, most construction within the floodway is prohibited.

  • Residential construction within the floodplain must elevate the lowest floor (including basement), and all associated machinery and equipment, to a minimum of the flood protection elevation.
  • Commercial or industrial development must elevate the lowest floor (including basement) or dry floodproof, including all associated machinery and equipment, to a minimum of the flood protection elevation.
  • Flood protection elevation is 1.5 feet above the base flood elevation or depth of flooding defined for the regulatory floodplain.
  • Projects on existing buildings in the regulatory floodplain are subject to “Substantial Improvement” rules. If a project (home remodel, commercial tenant finish, repairs, new addition, etc.) on an existing building triggers substantial improvement the entire building must be brought into compliance with the Floodplain Ordinance which can have significant financial implications. Substantial Improvement occurs when the construction cost reaches 50% (or greater) of the existing market value of the building (excluding land value). See Floodplain Entrance Requirements(PDF, 99KB)  for more info on Substantial Improvement requirements.
  • Elevation certificates are required for all structures built within the regulatory floodplain

Read Denver’s Floodplain Ordinance (Article V, Chapter 56, Revised Municipal Code)

City and County of Denver "Flood Protection Handbook"(PDF, 2MB)

FEMA "Homeowner Guide to Retrofitting: Six Ways to Protect Your House From Flooding"

Red Cross Clean Up a Flooded Home

FEMA "Repairing Your Flooded Home"

City and County of Denver "Homeowner's Guide to Runoff"(PDF, 496KB)

All construction (even remodels) located in the regulatory floodplain are required to obtain a Sewer Use and Drainage Permit (SUDP) for floodplain use. Find additional information about the requirements and supporting documents on the Development Services SUDP page under Requirements for Specific Project Types.

Resources for Developers

All development projects for properties or parcels located in the regulatory floodplain are required to obtain a Sewer Use and Drainage Permit (SUDP) for floodplain use. As of August 2018, the SUDP application has been combined with electronic building permit applications for a more streamlined submittal process and faster review times for many SUDP customers. SUDP reviews will now start when a building permit application is received.

Find additional information about the requirements and supporting documents on the Development Services SUDP page under Requirements for Specific Project Types.

Floodplain regulations are summarized in the Storm Drainage Design and Technical Criteria Manual - Floodplain Ordinance (Chapter 4)(PDF, 5MB)

Flood Planning and Projects

The City and County of Denver works with MHFD and FEMA to study flood risk and update flood maps through a Flood Hazard Area Delineation (FHAD), and the FHAD is sometimes paired with a watershed master plan called an Outfall Systems Plan (OSP) or a Major Drainageway Plan (MDP)

About Mile High Flood District (MHFD)

The Mile High Flood District was established by the Colorado legislature in 1969, for the purpose of assisting local governments in the Denver metropolitan area with multi-jurisdictional drainage and flood control problems. MHFD covers an area of 1608 square miles and includes Denver, parts of the 6 surrounding counties, and all or parts of 33 incorporated cities and towns. The population within MHFD is approximately 2.8 million people.