Flood Alert System
The City of Petaluma has installed and maintains a computerized Flood Alert System to enhance its ability to provide timely emergency flood response and evacuation warning to residents in flood prone areas. This system was originally installed 15 years ago after the catastrophic floods of 1982 and has recently been updated. The system consists of ten stations which monitor river levels, rainfall and weather data.

The City of Petaluma maintains an Emergency Operations Center (EOC). Emergency procedures are initiated during a flood event. These procedures were used for the first time during the 1995 flooding. Data from stream monitoring stations is radio relayed to a central computer and a central base station at the City’s Emergency Operations Center in the Police Department. Data is logged to files by the computer. The intent of the monitoring system is to enable personnel to study the cumulative impact, in real time, of inclement weather on various areas of the City. In general, when a rainfall rate of ½ inch per hour continues for more than one hour, emergency personnel begin continuous monitoring of river levels. Weather records are kept on file to document flood events and flood related claims.

As certain water elevations are registered on these gauges, various City procedures are activated. The first of these procedures is the activation of the City’s Emergency Operations Center (EOC). Once activated, City staff begins to execute standard management operation plans.

Five evacuation plans exist for the Payran area, which has been flooded most frequently over the past 20 years. These plans are labeled and prioritized, with the lowest topographical areas designated as most at risk for flooding. Once the evacuation order is given, field personnel go door-to-door to notify residents that they must leave.

When stream gauge readings reflect a pre-determined level, the National Weather Service Alert System is activated, and a flash flood warning is automatically announced to the National Oceanic and Atmospheric Administration (NOAA). These warnings are relayed as standard radio and TV broadcasts. In addition, the Sonoma County EOC releases warnings to the media; however it is up to the media to distribute the information at their discretion.