Foothills
Boulder County floodplain work needs review before construction
A Porch Note from Colorado Porch — plain-English local details for all 64 Colorado counties.
Anyone who watched the September 2013 flood tear down Boulder County’s canyon drainages knows how far the water can reach when it wants to. Floodplain review grew out of lessons like that, and it covers far more than big new buildings.
Work in a regulatory floodplain often needs a permit before construction starts. Some smaller projects fit under a General Floodplain Development Permit. Other work needs its own permit through the county’s Floodplain Management Program. Either way, the review is meant to happen first.
The reach is wider than people expect. Filling, grading, repairs, bridges, additions, and any work in a stream can all raise questions, and the risk is not limited to homes right on the water. Creeks, irrigation ditches, narrow canyon drainages, and low spots that sit dry most of the year can all fall inside a mapped floodplain. The ground looking calm in June says nothing about where the water goes in a storm.
So the first move is to learn whether the parcel sits in a regulatory floodplain, then talk to Boulder County Floodplain Management about what your specific project needs. The review is built to happen before fill is placed or a foundation is poured, which is the whole point of asking while a project is still on paper.
Sources
Official or primary sources used for this note. Local details can change, so confirm before acting.