Removing Matilija Dam:
- Why Remove Matilija Dam?
- Objectives
- Benefits from Removal
- Impacts: Habitat
- Impacts: Sediment
- Matilija Dam spilling
Final Design:
- Project Description
- Sediment Management
- Slurry Disposal
- Levees
- Bridges
- Robles Diversion modifications
- Arundo (giant reed) management
- Our Comments
Feasibility Study:
Early Progress:
Background Information:
About the Matilija Coalition:
Sediment:
Over the past half century the capacity of the Matilija reservoir has
been reduced by over 90% mainly due to the 6 million cubic yards of
sediment trapped behind the dam. This has rendered it an obsolete structure
that no longer serves a purpose for flood control or water storage. The
dam's effectiveness as a sediment trap has resulted in the erosion
of beaches downstream that rely upon the Ventura River. These
problems were predicted before, during, and after the construction of
the dam, (see history) and today we are witnesses
to the results. The reservoir storage is predicted to be zero by 2020.
This is the back side of the dam with the water drained out of the reservoir.
Current estimates place the sediment volume impounded by the dam at approximately 6 million cubic yards. Over half of this volume is sand, once destined for the beaches of south Ventura County.
This figure shows the historic storage volume and sediment deposition of the reservoir. The reservoir storage is predicted to be zero by 2020.
This diagram shows the current size of the reservoir. Although there is still considerable surface area, the water depth is very shallow (1-30 feet)
This figure shows the compostion of sediments trapped in the reservoir.
The dam traps the coarse particles
(sand, gravel, and cobble) which settle out in the reservoir, while passing
much of the finer silts downstream. This not only impacts the beaches,
but also the biological integrity of the lower reaches of the Ventura
River which now lacks gravel spawning beds for fish.