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E.4: How to Address Adverse Effects

Adverse effects to floodplains include increasing flood elevation or velocities upstream or downstream, modifying the function or value of the floodplain, and encouraging the occupancy of the floodplain. If you anticipate that your project will have an adverse effect to the floodplain, then you should consider ways to avoid those effects, minimize the effects, and if necessary, compensate for the effects. When possible, all projects should be designed to avoid adverse effects to floodplains. If adverse effects cannot be avoided, develop appropriate treatment measures into the scope of work so adverse effects are reduced and minimized. Listed below are some of the possible adverse effects that your project may have, together with possible treatment measures that you may include in your project to avoid, reduce or minimize, or compensate for adverse effects. The list is illustrative, and does not include all adverse effects that a project may have or all of the ways to potentially treat those effects.

Adverse Effects

  • Increase floodplain elevations or velocities upstream or downstream

Treatment Measures

  • Consult with the floodplain manager and obtain a permit
  • Acquire a “no-rise” certification
  • Construct retention ponds Treatment Measures
  • Expand the floodplain through excavation

Adverse Effects

  • Occupy the floodplain with a building or structure

Treatment Measures

  • Consult with the floodplain manager and obtain a permit
  • Acquire a “no-rise” certification
  • Design the building or structure to accommodate flooding
  • Choose a location outside the floodplain for the building or structure

Adverse Effects

  • Project encourages occupancy of the floodplain Treatment Measures

Treatment Measures

  • Restrict occupancy of the floodplain through zoning
Last Updated: 
07/24/2014 - 16:00
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