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.
The Santa Clara Valley Water District maintains a Stream Maintenance Program to protect and manage more than 275 miles of streams in the county. A key part of the program is a levee-safety program for approximately 100 miles of levees along local streams.
The efforts are part of the Clean, Safe Creeks and Natural Flood Protection Plan. Approved by county voters in 2000, the measure created a 15-year program funded by a modest parcel tax to provide more flood protection along miles of creeks and to care for those improvements through an aggressive maintenance program.
Inspections look for many things that can affect levee integrity, including overgrown vegetation, burrowing rodents and/or erosion. When an inspection finds a problem, appropriate preventative measures are taken to ensure the safety of the levee, as well as nearby people and properties. Adequate levee maintenance also ensures our ability to access and service streams during an emergency, such as a flood event.
What we do for levees.
Vegetation growth, if abundant, can restrict channel capacity, particularly at constricted locations such as bridge overpasses, culverts and other river 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.
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, sometimes to the point of collapse.
Erosion and scour are probably the leading cause of levee failures during flood events. Erosion or scouring commonly occurs along non-protected levee and bank slopes.
If you have questions or concerns about this project, contact the Santa Clara Valley Water District Watershed Hotline at (408) 630- 2378.