|Rolling Acres is a subdivision located within a larger area known as Plainfield, or West Plainfield. It is a small residential area comprised of approximately 50 properties of various sizes, located directly east of the Yolo County Municipal Airport along County Road 96. See Attachment A for location map.
Approximately 40% of these properties are within the area of 1% chance of annual flooding, commonly known as the 100-year floodplain. See Attachment B for area map with FEMA flood hazard zones. It is estimated that residential development in this area began over three decades ago. Given the location of these properties relative to the floodplain, localized flooding occurs frequently. Over the years, the Rolling Acres residents have sought assistance from the County to help mitigate the effects of flooding. Due to several factors including, but not limited to, development patterns in the region, siltation of natural waterways, and climate change, localized flood events are becoming more frequent and the effects more severe.
Following some localized flood events in 2019, several meetings were held with representatives of FloodSAFE Yolo 2.0 (“FSY2.0” is a joint effort between the County and the Yolo County Flood Control and Water Conservation District) and elected officials. The purpose of these meetings was to identify the issues and find possible solutions to address the residents’ concerns regarding these instances of localized flooding. In these meetings, the residents listed what they believed were some of the reasons for flooding in their area. Some were things that potentially could be addressed locally and quickly, such as the cleaning of sloughs and ditches that were subject to public agency maintenance responsibility, while others were of larger scale and costs, such as the revival of previous efforts to divert storm waters from the area to Putah Creek.
One thing that became apparent in these meetings was that numerous drainage and hydrological studies had been done over the years in different areas but had not resulted in any concrete project. To understand if past hydrologic and hydraulic analysis could eliminate the need to commission new studies and/or modeling to implement specific improvements to reduce flood risk in the area, FSY2.0 funded a $14,300 contract with a local expert firm, MBK Engineers. Specifically, MBK was tasked to summarize and review relevant drainage reports and studies conducted over the last 40 years.
MBK Engineers compiled a comprehensive list of 26 relevant hydrologic and hydraulic studies which was reviewed by the County and Rolling Acres residents. Once the list was finalized, MBK Engineers’ review of 23 documents showed many of the past studies utilized outdated modeling and therefore weren’t helpful in identifying a solution that could be implemented without further studies. The MBK report, "Plainfield Studies Summary Report" is provided as Attachment C to this staff report.
A few studies did analyze potential regional flood reduction strategies. These strategies typically focused on diverting flows to Putah Creek from Chickahominy Slough, Moody Slough or Dry Creek. These studies, however, were also based on outdated hydrologic standards and outdated hydrologic models. In summary, the review revealed that no study or models currently exist that can be implemented at this time without further hydrologic and hydraulic analysis.
Despite this, the effort still provided helpful information. The conceptual regional solutions to divert flows to Putah Creek did emerge as top candidates in terms of reducing flood concerns in the larger region. However, this potential solution comes with significant challenges. To successfully implement a flood control project of this magnitude significant local funding would be required for design, environmental compliance, right of way, utility relocation, capital, and ongoing operational costs. Since there is no existing County funding source for building or operating and maintaining flood control improvements, a tax assessment and formation of a new district would need to be voted on by the property owners who would benefit, through a Prop 218 process and LAFCo consideration.
While grant funds may be available for a portion of the capital costs for construction, a hydrologic and hydraulic study and preliminary design work would need to be completed first which is estimated to cost between $250,000 to $500,000. Staff is investigating whether grants may be available that would fund this work. Typical grant programs for flood mitigation projects require a cost-benefit ratio greater than 1, so an engineer’s report would also be needed to show regional benefits in excess of the project costs which are unpredictable at this time. For example, small regional projects may range from $1M to $15M while large-scale regional projects may easily exceed $50M to $100M. Given that the County does not have experts in this field, there would be additional staffing costs to this effort, by either hiring specialized staff or by hiring and managing a consultant.
The challenge for the Rolling Acres area is that the scale of potential damages is small when compared to the scale of the project required to address the localized flooding problem. This is taken into account when looking at a cost-benefit ratio for solutions. Since the cost to divert regional flows is likely much greater than the benefits provided to the Plainfield area watershed alone, such a project would need to demonstrate benefits to the region as a whole to successfully compete for grant funds. The jurisdictions needed as partners in this effort include the City of Davis, City of Winters, the University of California at Davis, various reclamation districts, and the Department of Water Resources. Staff cannot assess at this time whether the regional benefit might exceed the cost of the project, nor whether any of the potential public agency partners, listed above, are interested in pursuing a planning effort related to flood risk reduction.
Another result of this collaborative process was the identification of smaller-scale improvements that could mitigate, but not solve, the flooding problem. Three strategies were identified, all of which require private property owner initiative.
For the first two strategies, the County cannot compel property owners to perform this work on their property. Nevertheless, County staff mailed letters to approximately 70 property owners in the Plainfield area urging them to perform this work for the upcoming winter season to allow for proper flow of storm waters.
- Cleaning out the local creeks and sloughs that run through private property
- Implementing winter tilling practices that minimize runoff
- Raising repetitive loss homes through a FEMA mitigation grant program
The third alternative will require significant property owner financial contribution, but it is a viable option to eliminate future flood losses. The region has had some success with this program in the past. In 1997 the YCFCWCD applied for and was awarded $2.6M from the Governor’s Office of Emergency Services for implementation of the “Madison Flood Hazard Mitigation Project”. The Project proposed to elevate 80 structures at least one foot above the 100-year base flood elevation and required property overs to pay 25% of the total cost, with the grant program funding the remaining 75%. The 1997 funding application describes the Project thusly, “Flooding in the area is a recurring problem with no apparent achievable solution due to the complexity of the problem and the interrelationships with other local flood problems.” The application further notes that “…elevating the structures to one foot above the 100-year flood elevation is the most feasible mitigation for this area at this time. It does not solve the problem, but it will mitigate losses…”. It is worthy of note that only three (3) properties elected to participate in the structure elevation project.
Staff have developed three options for Board consideration:
- Keep the status quo.
This option recognizes that flood protection in areas of high risk is largely a responsibility of the property owners, and that the County has no jurisdiction to improve drainage on private property. Property owners will have to work individually or collectively to find flood protection measures through FEMA (see option 3 below) or grant funding. Staff and partner agencies would continue to coordinate implementation of best management practices for drainage in the County's area of maintenance responsibility. Staff would also continue to educate private landowners on actions that could be privately undertaken to improve drainage on private property.
- Pursue a regional approach as described above.
This option is the preferred option by the residents that have worked with staff, and will require partnerships with the stakeholders identified in the staff report and local funds to prepare the initial studies. Provided there is interest and financial commitment from all affected jurisdictions, and agencies, in addition to community support for a tax measure, staff estimates that preparation of the study that will identify the actual project could take 18 months. Once a project is identified and the decision to move forward is given, a California Environmental Quality Act report must be prepared, which will take approximately 12 months. During this time staff would identify potential funding sources for construction. Final engineering and permits will take approximately 24 months. Construction timing is dependent on project design and scale but could take between 12 and 24 months. In addition, a yet unknown maintenance and operation cost will have to be borne by the benefited through the passing of a Prop 218 vote which could take a year to complete. Actual maintenance and operation costs would be calculated once final project design is completed. In total, staff estimates this approach to be in the 6 to 8-year timeframe. Until then, the status quo conditions would remain.
Staff recommends the Board receive public testimony, consider the options developed by staff, and provide staff direction.
- Direct staff to assist property owners in the Rolling Acres area to pursue FEMA grant program funding to raise repetitive loss homes above flood levels. This option was presented to the residents during meetings with staff but there was little interest by the residents in pursuing this option. It should be noted that this option is more timely, efficient, and cost-effective than the option described above and would mitigate against losses from recurring nuisance flooding.