Many areas of Santa Clara County rely on local streams to keep floodwaters away from homes, businesses, and transportation routes. Several of those streams depend on levees to hold back floodwaters.
Valley Water operates a Stream Maintenance Program that protects and manages more than 333 miles of streams in the county. A key part of this program is ensuring about 100 miles of levees along these local streams are in good condition.
The Safe, Clean Water and Natural Flood Protection Program, a parcel tax that county voters renewed in 2020, provides funding for various efforts, including flood protection work along miles of creeks and the proactive maintenance of those projects.
During levee inspections, Valley Water workers look for issues that could weaken the levee, such as overgrown vegetation, burrowing rodents, and erosion. If we find a problem, our teams take the necessary steps to fix it and prevent future issues. This maintenance helps keep the levees safe for nearby people and properties. It also ensures we can access and service streams in emergencies, such as flood events.
Excessive vegetation can block water flow in a creek, particularly in narrow areas such as bridge overpasses, culverts and other creek crossings. Thick vegetation on a levee slope makes it difficult to spot animal burrows. Roots from plants can also damage the levee’s integrity. Managing vegetation properly allows for better levee inspections to occur.
Burrowing animals can create a complex maze of tunnels in a levee and its foundation. These holes can weaken the levee, increasing the risk of “piping,” where water flows through the burrow. Piping erodes the soil and enlarges the tunnels, which can lead to sloughing, slumping or failure of the levee. Erosion and scouring can also contribute to levee failures during flood events. Erosion or scouring commonly occurs along non-protected levee and bank slopes. We can use various techniques to address issues caused by burrowing animals, such as compacting the surface, filling in burrows with soil or slurry material, or installing barriers.
Before: Stevens Creek downstream of La Avenida Street, Mountain View: The east levee was eroded due to January 2023 storm events. (Photo taken March 2023.) 
During: Stevens Creek downstream of La Avenida Street, Mountain View: Excavation of eroded levee slope as part of repairs. (Photo taken August 2023.) 
After 1: Stevens Creek downstream of La Avenida, Mountain View: east levee repaired. (Photo taken October 2023.) 
After 2: Stevens Creek downstream of La Avenida, Mountain View: One year later, the east levee remains in good condition. (Photo taken November 2024.)
In 2023, Valley Water repaired the levee along Stevens Creek downstream of La Avenida Street in Mountain View. Approximately 100 feet of the creek’s eastern levee eroded during high flows caused by atmospheric rivers early that year. In accordance with permits obtained through our Stream Maintenance Program, Valley Water repaired the levee later that year. We dug out the existing slope, brought in clean fill material, compacted it, and then covered the area with hydroseed and a biodegradable erosion control blanket.
Levee inspection and maintenance work like this is one of the many ways Valley Water helps reduce flood risks in Santa Clara County.