• Floodplains


    Jefferson County FloodplainsColorado winter storms and heavy rains have a big impact on flood potential. A floodplain is an area near a water source that is at a greater risk of being covered by flood water.

    Take a look at the Jefferson County Floodplains brochure View document in PDF format. with answers to some of the most frequently asked questions.

    The Local Flood Hazard

    The local flood hazard is discussed in detail in FEMAs January 20, 2016 Flood Insurance Study (FIS). Read a portion of the FIS, including the Community Description and Principal Flood Problems.View document in PDF format.  

    Floods are one of the most common hazards in the United States. However, all floods are not alike. Riverine floods develop slowly, sometimes over a period of days. Flash floods can develop quickly, sometimes in just a few minutes, without any visible signs of rain. Flash floods also often have a dangerous wall of roaring water that carries a deadly cargo of rocks, mud and other debris, which can sweep away many things in its path. Overland flooding occurs outside a defined river or stream, such as when a levee or dam is breached. Flooding can also occur from a dam break producing effects similar to flash floods. Be aware of flood hazards no matter where you live, but especially if you live in a low lying area, near water or downstream from a dam. Even very small streams, gullies, creeks, culverts, dry streambeds or low lying grounds that appear harmless in dry weather can flood.

    Planning and Zoning staff can answers questions related to floodplain management, including determining if a property is located within a floodplain within Jefferson County. Copies of elevation certificates can be obtained on the Floodplains Elevation Certificates page or by contacting the Planning and Zoning Division.

    For additional floodplain information or questions please contact the Jefferson County Planning and Zoning Division at 303-271-8700. In addition, see our FAQs regarding floodplains in Jefferson County.

    Flood Safety

    1. Be aware of possible flash flooding hazards. If there is any possibility of a flash flood, move immediately to higher ground. Do not wait for instructions to move.
    2. Listen to radio or television stations for local information.
    3. Be aware of streams, drainage channels, canyons or other areas known to flood suddenly. Flash floods can occur in these areas without such typical warning signs as rain clouds or heavy rain.
    4. If local authorities issue a flood watch, prepare to evacuate.
      • Secure your home. If you have time, tie down or bring outdoor equipment and lawn furniture inside. Move essential items to the upper floors.
      • If instructed, turn off utilities at the main switches or valves. Disconnect electrical appliances. Do not touch electrical equipment if you are wet or standing in water.
      • Fill bathtubs with water in case water becomes contaminated or services cut off. Before filling the tub, sterilize it with a diluted bleach solution.
    5. Do not walk through moving water. Six inches of moving water can knock you off your feet. If you must walk in a flooded area, walk where the water is not moving. Use a stick to check the firmness of the ground in front of you.
    6. Do not drive into flooded areas. Six inches of water will reach the bottom of most passenger cars causing loss of control and possible stalling. A foot of water will float many vehicles. Two feet of water will wash away almost all vehicles. If floodwaters rise around your car, abandon the car and move to higher ground, if you can do so safely. You and your vehicle can be quickly swept away as floodwaters rise.

    Flood Insurance

    The National Flood Insurance Program is a federal program that enables property owners to purchase insurance protection against losses from flooding.

    The Insurance Program is administered by the Federal Insurance Administration, a part of the Federal Emergency Management Agency.

    The Federal Insurance Administration has state-licensed insurance companies' agents and brokers sell flood insurance to you!

    Contact your insurance agent for more information on the National Flood Insurance Program View exit disclaimer policy page for links to third-party websites. or call 1-888-FLOOD29.

    Property Protection Measures

    There are a number of measures to take to protect your property from damage from a flood.

    • Check to see that you have slopes that drain away from your homes exterior walls a minimum of seven feet on all sides.
    • Check your gutters and downspouts to ensure they drain away from your foundation. Use downspout extensions if required. Also make sure your downspouts do not drain to your neighbor’s foundation.
    • Do not dump or throw things into gulches and ditches, including branches, grass clippings, garbage, dirt or other material because debris clogs drainage ways, creates hazards, and is not permitted.
    • Report any dumping in gulches and ditches by calling Planning and Zoning at 303.271.8700.
    • Always check with Jefferson County before building, grading, fencing or otherwise altering your property. Any work with our Floodplain Overlay District requires a Floodplain Permit from Jefferson County. Call Planning and Zoning at 303.271.8700 with any questions.
    • Check to see if you have current flood insurance policy for your property. Homeowners insurance typically do not cover damage from floods.
    • Jefferson County participates in a federal program that provides lower flood insurance rates for property owners in Jefferson County. Verify to ensure the insurance covers both the structure and contents. For additional information about your flood insurance issues, contact your insurance agent.

    Natural and Beneficial Functions

    Floodplains in Jefferson County are the lower areas adjacent to rivers, lakes, and creeks that are periodically flooded at intervals of varying frequency. Floodplains are important components of their respective watersheds. Floodplains are hydrologically important, environmentally sensitive and ecologically productive areas within a watershed that perform many natural functions.

    Floodplains contain a wealth of cultural and natural resources that are of enormous value to society. Riverine floodplains, such as the floodplains found in Jefferson County, vary in steepness, width, stream flow, sediment deposition and erosive characteristics. The natural functions that are associated with a particular floodplain depend in part on its location within this system. The frequency, duration and extent of flood events will also vary among different types of floodplains, dependent upon their hydrology, geology, and amount of floodplain development.

    Floodplains are formed and modified by the dynamics of stream and river migration and periodic flooding. Although many riverine floodplains usually flood during the spring storms, they can also experience multiple flood events within the same year with duration varying from hours to days. Periodic flooding of riverine systems and the related processes of erosion and deposition determine, to a considerable extent, the shape of the floodplain; the depth and composition of soils; the type and density of vegetation; presence and extent of wetlands; richness and diversity of wildlife habitats; and depth to the groundwater.

    The major flood conveyance component of the floodplain is the floodway. The National Flood Insurance Program defines the floodway as that area of the watercourse and adjacent floodplain necessary to carry the base flood without increasing the water surface elevation more than a designated amount (generally one foot). The base flood is the flood that has a one percent chance of being equaled or exceeded in a given year. Communities are required to prohibit development within the floodway that would cause an increase in flood heights. This requirement has the effect of limiting development in floodways that in turn helps to maintain some of the floodplain’s most important natural resources and functions.

    There are a number of walking paths and bike paths throughout many of the floodplains in Jefferson County. These paths provide an opportunity for out citizens to enjoy the vegetation and wildlife that thrives in our floodplains.

    Map of the Local Flood Hazard

    Planning and Zoning staff can answers questions related to floodplain management, including in determining if a property is located within a floodplain within Jefferson County. In addition you can access the Jefferson County interactive mapping application

    Flood Warning System

    The most comprehensive weather information is obtained by listening to a NOAA Weather Radio. Weather Radio is operated by National Weather Service offices across the country and broadcasts frequently updated recordings containing current high climatological data. During threatening weather, live broadcasts issue warnings for winds, large hail, tornadoes, flash floods and winter storms. You can purchase a tone-alert NOAA Weather Radio at many local electronic stores.

    The Emergency Alert System (EAS) is one tool that Jefferson County can use to warn its citizens in case of an impending disaster on participating radio and television stations. In most cases however, the National Weather Service has already activated EAS.

    The other system we use more regularly is commonly referred to as “reverse 911”. To ensure that you phone number is registered to your home address for targeted emergency calls, please visit the Jefferson County Sheriff's Office CodeRED page.

    We also regularly use other means of local media to put out critical information such as evacuation orders, sheltering information and other emergency messaging.

    Floodplain Development Permit Requirements

    Always check with Jefferson County before building, grading, fencing or otherwise altering your property. Any work with our Floodplain Overlay District requires a Floodplain Permit from Jefferson County. Call Planning and Zoning at 303-271-8700 with any questions including reporting of an illegal floodplain development

    Substantial Improvement/Damage Requirements

    "Substantial improvement" means any rehabilitation, addition, or other improvement of a building when the cost of the improvement equals or exceeds 50 percent of the market value of the building before start of construction of the improvement. Substantial improvements shall be counted cumulatively for a period of 5 years from the Start of Construction date of the first approved building permit. The term includes buildings that have incurred "substantial damage." "Substantial damage" means damage of any origin sustained by a building when the cost of restoring the building to its pre-damaged condition would equal or exceed 50 percent of the market value of the building before the damage occurred. Substantial damage is determined regardless of the actual repair work performed.

    Substantial improvement or damage does not, however, include any project for improvement of a building to correct existing violations of State or local health, sanitary, or safety code specifications identified by local code enforcement officials as the minimum specifications necessary to assure safe living conditions. Also excluded from the substantial improvement requirement are alterations to historic buildings as defined by the NFIP.

    Drainage System Maintenance

    Jefferson County prohibits impeding or interfering with the flow of storm water in the natural drainage ways, unimproved channels or watercourses, or improved ditches, channels or canals in such a manner as to cause flooding where it would not otherwise occur. This includes debris, branches, or other material that may interfere with the flow of water.

    Call Planning and Zoning at 303-271-8700 with any questions regarding maintenance or including reporting of a violation.