Lower Poudre River Flood Recovery and Resilience Master Plan

In response to the devastating flood of September 2013, the Coalition for the Poudre River Watershed (CPRW) hired Lynker to develop a flood recovery and resilience master plan for the Lower Poudre River. The project was funded by a grant from the Colorado Department of Local Affairs (DOLA) Community Development Block Grant Disaster Recovery (CDBG-DR) Resilience Planning program.

The master planning effort combined scientific and engineering analysis with community collaboration to identify and prioritize opportunities to improve river resilience and river health. Components of the master plan include reach-by-reach analyses of changes to the historical channel, assessments of geomorphological and ecological values, identification of vulnerabilities, and sediment transport modeling. Lynker led a team of scientists, engineers, geomorphologists, ecologists, modelers and designers from Otak, AlpineEco and LVBrown Studio to create an informative, user-friendly master plan that provided recommendations through the project area.

A sediment transport model was built for the 36 miles of river in the project area, utilizing existing HEC-RAS model cross-sections to determine sediment transport capacity on a reach-by-reach basis. The model focused on the use of total effectiveness, which uses the river flow regime and their respective probability of occurrence to determine the river’s total sediment transport potential over time. Sediment bed samples were collected by performing pebble counts at pre-determined reach cross-sections. Each field visit was thoroughly documented with field data sheets and photos from a GPS camera.

The data collected for the project was used to compile a reach-by-reach river characterization and assessment to determine areas with the greatest need for future restoration work. The assessment included metrics for flood hazards, geomorphology, ecological and aquatic habitat, social vulnerability and local priorities. For instance, the project steering committee and the local community put a high emphasis on the integrity of the Poudre River Trail, a 21-mile paved path the closely follows the river for much of the project area. Therefore, the Poudre River Trail was included as an element of river assessment and the final Poudre River prioritization scoring.

The large project area showcased Lynker’s ability to develop river restoration projects through community outreach and adaptive priorities. The planning process included an extensive public outreach effort that drew on landowners and local community experiences to pinpoint vulnerable areas and important assets. Based on these meetings, a cultural aspect of the community was accounted for when developing restoration projects. Illustrative conceptual designs were developed for the high priority reaches while taking into consideration ongoing projects within the reaches. The master plan and sediment model developed for the Lower Poudre are intended to be continuously evaluated during future planning actions or assessments to make reach-scale decisions that can help inform the solutions that may be best for a reach.