Consideration and Adoption of Resolution No. 2021-52:  A resolution approving the Intergovernmental Agreement between Arizona Board of Regents, for and on behalf of, the University of Arizona and the City of Flagstaff for the Flagstaff Flood Mapping Program.

Approval of the Intergovernmental Agreement ("IGA") between the Arizona Board of Regents, for and on behalf of, the University of Arizona and the City of Flagstaff will formalize the Flagstaff Flood Mapping Program. The City seeks to collaborate with the Arizona Geological Survey Center for Natural Hazards (“AZGS”), a department within the University, to receive scientific reports regarding the geomorphic conditions following flooding events. The AZGS is Arizona’s leading geologic investigations agency with expertise in geomorphology and the documentation and monitoring of natural disasters. Under this IGA, the parties intend to develop and deliver a targeted Flagstaff Flood Mapping Program where the AZGS will provide the City scientific reports that will inform data-driven decisions related to flooding mitigation and improvements. This agreement will begin upon full execution and will continue for a 5-year initial term, with the ability to renew for an additional 5-year term.

Water Services has an on-going budget of $200,000 per year in Water Fund Stormwater Section account number 206-99-000-0000-0-4277 for contingency needs. This IGA commits a not-to-exceed amount of $50,000 annually as described in the IGA, on an as-needed basis as agreed by both parties. The City agrees to waive indirect costs so that the total funding provides a greater direct benefit to the project.

Collaborating with the Arizona Geological Survey supports Council Adopted Water Policy E.2. on Flood Control, E.3. Stormwater and E.4. Watershed Management.

Priority Based Budget Key Community Priorities and Objectives
Key Community Priority: Environmental Stewardship
Key Community Objective: Strengthen Flagstaff’s resilience to climate change impacts on built, natural, economic, health, & social systems
Key Community Objective: Promote, protect & enhance a healthy, sustainable environment
& its natural resources

Regional Plan
Goal WR.5. Manage watersheds and stormwater to address flooding concerns, water quality, environmental protections, and rainwater harvesting.

There has not been previous council direction on this topic.

1. Approve the IGA; or
2. Do not approve the IGA and direct staff to engage the AZGS on an annual basis in a less formal manner. This option greatly reduces the flexibility of the parties to respond quickly in order to capture critical evidence immediately following a flooding event.

Investigating post-fire flooding events in Arizona is one of the core focus areas of the AZGS. Scientists with the AZGS are often at the forefront of documenting the impacts that rain events have on the topography of burn areas and the potential impacts to residents and urban areas. While AZGS scientists are often visiting and documenting sites as part of their core function an agency can ensure scientists are collecting information critical to their needs through funding their work. This IGA allows the City and AZGS to respond quickly while the geomorphic evidence is still fresh following a flooding event.

This IGA formalizes and strengthens the partnership that has loosely existed since the Schultz Fire in 2010. The execution of this IGA allows staff to quickly formulate a work plan with the AZGS that they can execute within a short time period in order to document accurate post-flooding conditions. The AZGS will provide professional geomorphic reports regarding post-flooding and debris flow hazards in the identified field sites, including: (a) recommendations for drainage that is more responsive to potential flood events; (b) recommendations of designs for detention basins or sediment retention structures; (c) creation of a map of incision and aggradation reaches, inundation extents and descriptions of deposits and interpreted flow types; (d) documentation of undisturbed deposits focusing on areas within the City (description of in-place deposits including estimates of grain size, sorting, matrix- vs clastsupported, thickness, and flow type – flood, or hyper-concentrated debris flows); and (e) the collection of deposit samples for lab analysis (particle size distribution).

This IGA specifies that up to $50,000 annually may be paid to Arizona Geological Survey to conduct professional geomorphic research and create reports regarding post-flooding and debris flow hazards in City of Flagstaff watersheds. There are possible economies of scale with this IGA where leveraging of funds or staff time might be possible. The AZGS is funded by multiple federal agencies including the U.S. Forest Service. The AZGS has conducted separate post-Museum Fire geomorphic monitoring on U.S. Forest Service lands. Further, the AZGS has been involved in the Bureau of Land Management Joint Fire Science Project Quantified Wildfire Risk Assessment where the AZGS was separately engaged to assess and quantify post-flooding and debris flow hazards and uncertainties downstream of a forest boundary.

We believe this information collected by the AZGS will help Stormwater and City Council make data-driven decisions. The biggest benefit is that the information provided under the IGA will identify the change in flood frequency and flood risk. The AZGS will provide the City with an understanding of drainages that is more responsive and the potential amount of debris to expect when designing detention basins or sediment retention structures. The City will gain a better understanding of the scour/aggregation potential remaining in a burned watershed and have a better understanding of what material will mobilize in future storms. The City will acquire data to help calibrate of verify hydraulic models and have data to assist staff to assess risk to washout or damage to water infrastructure (water or sewer pipelines.).