Much of Santa Clara County is dependent on the ability of local streams to keep floodwaters away from homes, businesses, and transportation routes. Many of those streams rely on levees to hold back floodwaters.
Valley Water implements a Stream Maintenance Program to protect and manage more than 333 miles of streams in the county. A key element of the program is a levee-safety program for approximately 100 miles of levees along local streams.
The efforts are funded in part by the Safe, Clean Water and Natural Flood Protection Program. Renewed by county voters in 2020, the measure continues funding via a modest parcel tax to provide flood protection along miles of creeks and to care for those improvements through an aggressive maintenance program.
Levee inspection
Inspections comprise looking for many things that can affect levee integrity, including overgrown vegetation, burrowing rodents, and/or erosion. When an inspection results in an identified problem, appropriate corrective or preventative measures are taken to ensure the levee continues to function as constructed, for the safety of nearby people and properties. Adequate levee maintenance also ensures our ability to access and service streams during an emergency, such as a flood event.
Vegetation management
Vegetation growth, if abundant, can restrict channel capacity, particularly at constricted locations such as bridge overpasses, culverts, and other creek crossings. Thick vegetation on a levee slope makes it difficult to detect rodent burrows. Root systems from vegetation can also damage the system’s integrity. Appropriate vegetation management allows for levee inspections to occur.
Burrowing animals and erosion
Burrowing animals can create an extensive and interconnected maze of burrows in a levee and its foundation. These holes can weaken the levee and contribute to levee failure by increasing the potential for “piping,” or water running through the burrow passage. Piping weakens the soil and enlarges passageways. This, in turn, weakens the structure of the levee, and can lead to sloughing, slumping, or failure. Erosion and scour can also contribute to levee failures during flood events. Erosion or scouring commonly occurs along non-protected levee and bank slopes. Various techniques can be employed to address burrowing animal- or erosion-related issues on levees, including surface compaction, filling burrows with soil or slurry material, or installation of physical barriers.
If you have questions or concerns about this project, contact the Valley Water Watershed Hotline at 408-630- 2378.