Floodplain Construction Rules

There are floodplain construction regula­tions to protect you and your neighbor.

Here is some basic guidance:

  • Check with the Community Development Department at 360.740.2696 before you build, alter, regrade, or fill on your property. You may be required by law to get a permit. Talk over what you want to do and make sure you can meet all the regulatory requirements.
  • The County’s home elevation guide has a summary of the rules for elevating a building and modifying a crawlspace that will help protect the building from flood damage.
  • Berms and other barriers are prohibited if they divert water onto other proper­ties. Play it safe and don’t move dirt without a permit.
  • Call the Community Development Department if you see construction or filling without a permit. An unper­mit­ted project may increase flooding on your property.
  • Our floodplain regulations are in Chapter 15.35 of the Lewis County Code.
  • These rules only impact new development. They do not affect existing buildings unless the building will undergo a substantial improvement.
  • Substantial improvement: A substantial improvement is where the cost of the improvements, remodeling, or addition is more than 50% of the value of the building. A substantial improvement project must meet the construction standards for a new building in the Special Flood Hazard Area.
  • Substantial damage: Repairs to a substantially damaged building that exceed 50% of the building’s pre-damage value are also considered substantial improvements. It does not matter if the building was damaged by a flood, fire, accident or other reason.
  • Call the Community Development Department at 360.740.2696 to find out more about these rules or see more details in FEMA's guidance and website.
  • More detailed information on floodplain construction rules are found in FEMA’s Floodplain Management Requirements Study Guide and Desk Reference. Note, though, that Lewis County has some requirements that are more restrictive than these national guidelines.


Contact the Community Development Department:

2025 NE Kresky Ave. Chehalis, WA