Your property in Lake County may be located within or near a designated 100-year flood plain, also known as a Special Flood Hazard Area (SFHA), as mapped on a Flood Insurance Rate Map (FIRM). To help you protect yourself and you property during flood events, the Flood and Lake Management Division of Public Works has provided you with the information found in this package. Please read this flyer for information on how floods occur in Lake County, as well as the brief guidelines on Flood Insurance, Flood Safety, actions you should take to reduce flood hazards, and the availability of County Flood Services.
Flooding in Lake County can be caused by streams, such as Scott's Creek or Putah Creek, and by lakes, such as Clear Lake or Blue Lakes. Flooding from streams and lakes have different characteristics. In mountainous terrain, flooding by creeks and small lakes occurs quickly in response to individual storms, and floodwaters recede quickly after the storm has ended. However, prolonged storm events can cause extended periods of flooding, and flat areas with poor drainage may also stay flooded for a long time. Floods can occur with little warning, as they did in January and March, 1995 and in January, 1997. Stream levels can increase over ten feet within hours of the storm's onset. Streams also carry debris, such as tree branches, that can cause property damage by slamming into structures, or cause a "log-jam", raising flood levels even higher. Bank erosion is common during flood events. Healthy vegetation on the bank of the stream, but not in the center, will help resist bank erosion and protect your property
Due to its size, Clear Lake responds more slowly to storm events and rises to flood stage only after prolonged, high intensity storms. When this happens, Clear Lake's natural outlet, Cache Creek, is too small to allow floodwater to leave the lake as fast as it enters. Contrary to popular belief, the Clear Lake Dam does not cause Clear Lake to flood. The dam can actually release water much faster than Cache Creek can flow. It is the narrow, shallow Cache Creek channel that slows the release of water from Clear Lake During a flood.
Some historical facts help demonstrate this situation. The highest level ever recorded for Clear Lake was in 1890, before the construction of the Clear Lake Dam. In March, 1995, water was flowing into Clear Lake over ten times faster than it could flow out through Cache Creek, and the lake rose over one foot per day. Additional damage can be caued when high winds accompany lake flooding, such as happened in 1983. Large waves can cause complete destruction of buildings, even though the depth of flooding is small. Although the lake can rise fast, it normally provides us with a couple of days warning to prepare for flooding on its shores. Unfortunately, lake flooding frequently lasts for weeks as it did in 1983, 1995, and 1998.
Your property may be high enough so that it has not flooded recently; however, the next flood could be worse. If you are in a flood plain, the odds are that someday, floodwaters will damage your property. Buildings located in designated flood zones have a 26 percent chance of being flooded during the period of a 30-year mortgage.
