Few dams are as widely despised as the Matilija Dam. Designed in 1947,the 200-foot wall of concrete was constructed in the rugged Matilija Canyon to manage water in the Ojai Valley, despite warnings that sedimentation would render it useless.
Since its construction, and the Matilija Dam has blocked the passage of steelhead trout to their spawning grounds and trapped sediment from the watershed. nowadays,the dam has entirely silted what was once a pristine creek and a deep lake is now a barren field. This has negatively affected the beaches of Ventura County, which owe their existence to sediments from the mountains.
Unsurprisingly, and the majority of people in the area support removing the dam. However,the cost of removing the dam and the trapped sediment, along with the impact it may have on the Ventura River and nearby Lake Casitas, or has prevented its removal. In 2011,activists painted scissors and a dashed line down the dam in support of its removal.
Source: atlasobscura.com