Flood Mitigation Projects
The 2016 Flood Protection Plan was based on a “study to quantify relative flood risk level within the watershed” … “to identify existing creek flooding concerns, prioritize those concerns, and propose potential alternatives for the mitigation of the highest priority concerns”. The District is currently focused on addressing flooding in two of the most at-risk areas in the County. Flood Mitigation projects will protect infrastructure and improve emergency access to the area by reducing flood risk at multiple road crossings.
Dam Rehabilitation Projects
Like all aging infrastructure, dams require rehabilitation to keep them working safely and effectively. The 2020 Dam Assessment Study categorized breach risk using the Joint Federal Risk Category method – an approach developed by multiple federal dam agencies for use in portfolio risk management (FEMA 2015). The Study prioritized rehabilitation projects to evaluate and implement the most cost-effective ways to alleviate current issues and protect against future ones.
|Dam 9 Regional Detention
Rehabilitation Projects typically include work on the type of items listed below:
Embankments -As earthen dams age, their steep, sloping sides can become unstable as their soil settles or as animals or people compromise the soil, vegetation, etc. The Dam Assessment Study found that approximately 25% of the risk of the District’s portfolio is associated with the embankments and parapet walls.
Principal Spillways -Water typically leaves a dam’s reservoir through its principal spillway. The spillway’s many elements can deteriorate over time and require reinforcement or replacement. The Dam Assessment Study found that only a small percentage of the District’s portfolio had principal spillway issues. In addition, to remediate existing issues the District will look to optimize the spillway capacity.
Auxiliary Spillways-Auxiliary spillways perform the critical unction of safely passing floodwaters without compromising the dam’s integrity. Erosion on an auxiliary spillway can result in damage and potential dam failure. The Dam Assessment Study found that more than 60% of the risk of the District’s portfolio is associated with the auxiliary spillways. Rehabilitation projects will strengthen the spillways and protect against future issues.