The Meadows Stormwater Flood Mitigation project addressed complications resulting from years of severe flooding events in Sidney, MT.

The Meadows Subdivision is located at the downstream end of a large drainage basin of nearly 1,000 acres that produces a significant amount of runoff. Residents in the subdivision have experienced severe flooding caused by rapid melting. The large basin contributes increased runoff volumes during rain and snow storms that overwhelm the existing culverts and spread stormwater through the neighborhood.

The most severe flooding occurred on February 8, 2015. While only 0.37 inches of precipitation was recorded, which is less than a 2-year rain event, the rapid snow melt in the basin caused significant volumes of runoff that inundated the drainage infrastructure and roadside ditches. The upgradient detention pond exceeded its capacity and released peak flows to the Meadows neighborhood. The pooling runoff threatened several homes in the area when it could not pass through the outfall culvert, which was already operating at maximum capacity. Volunteers from the community and fire department were onsite sandbagging and pumping water to prevent homes from flooding.

To mitigate the potential damages caused by stormwater flooding in the subdivision, the City of Sidney partnered with Morrison-Maierle to complete preliminary design and obtain grant funding for the stormwater improvements project. The project design includes modifications to the regional detention pond to increase storage and attenuate peak flows, new storm inlets, and a large diameter stormwater pipe to safely direct runoff out of the residential area.