Download the full document: CPW Post Flood Assessment and Guidelines (.pdf)
Severe flooding impacted rivers and streams in the Colorado Front Range during September 2013. The flooding had devastating effects on communities and infrastructure, but had many beneficial effects on river ecosystems and stream functions. Flooding is a natural component of river systems that is vital for many ecological and physical processes. Following the flood, rebuilding infrastructure was given top priority and permitting processes were suspended or expedited to facilitate reconstruction activities. In many cases, emergency reconstruction activities led to degradation of stream functions and aquatic habitat. Degradation was often associated with the creation of trapezoidal and armored channels. Initial monitoring following the flood showed variable impacts to fish populations, with changes in trout abundance ranging from -58% to +69% at sites that were severely impacted by the flood but not further altered during emergency reconstruction. Monitoring sites that underwent substantial channel alterations during emergency reconstruction had an average change in trout abundance of -95%. Floods may provide an opportunity to improve a variety of stream functions related to channel stability, flood conveyance, geomorphology, water quality, and habitat connectivity. However, programmatic constraints at both the state and federal level limit opportunities to improve rivers beyond their pre-flood condition. Addressing permitting and funding constraints prior to the next major flood could greatly improve the efficiency and effectiveness of emergency flood response while reducing long-term maintenance and stream restoration costs.