Why did you decide to create such a project? On February 3, 1998, the City of Palo Alto flooded. The El Niņo effect was in full bloom, it had been raining hard for a long time, and then a severe storm settled in, causing the San Francisquito Creek to spill over it's banks and flood a major portion of Palo Alto. The residents of Palo Alto and the neighboring communities were very upset and outspoken about having received no advanced warning. At that time there was no creek monitoring system. During the storm, the creeks were monitored by direct observation, with reporting done by radio.
After the need became evident, the Public Works Operations department examined the locations of existing City facilities near the creeks, and concluded that creek sensors could be installed and connected to the existing SCADA system. Over a period of a year and a half, five creek monitor points, the flood basin and tide monitors, and a rain gauge were added to the SCADA system, making their statuses immediately available at all times.
The initial goal of the system was to make current creek and rain information available to the Emergency Operations Center (EOC) to aid the Fire Chief in issuing timely notices to Palo Alto residents. After that, moving this information to the City's web page seemed the next logical step.
What kind of technology is used? The creek monitoring system is based on the City of Palo Alto's Water, Gas and Storm (WGS) pump station Supervisory Control And Data Acquisition (SCADA) System. This system monitors and controls the City's water, gas, and storm drain pump stations.
The creek monitoring sites use ultrasonic level detectors mounted above the water. These level detectors measure the distance from a transducer to the water surface using sound waves, like sonar. The time between the sending of the sound pulse and the receiving of its echo is converted to a signal representing distance. The detector is programmed with the distance from the transducer to the creek bed. The measured distance is subtracted from the programmed value and the difference is the creek depth.
We chose ultrasonic level detectors to measure the water level rather than pressure transmitters, bubblers or floats because of the amount of debris that can be carried down the creeks during rain events. We didn't want anything mounted in the creeks that could be hit or damaged during a storm by floating or submerged debris.
This depth value is converted to a digital signal and transmitted over the city's internal telephone wire network to the SCADA System, using four-wire modems.
The West Bayshore monitor site is unique in the system in that it uses radio to send the depth information, and has a DSL connection to make video still pictures of the creek and bridge available on the web.
How does the SCADA information get to the web? One screen on the SCADA System is designed for the creek monitoring web page specifically. This screen is displayed continuously on one of the SCADA system's view computers, where the image is captured every minute and then FTP'd to the web server, where it is inserted into a web page, and then posted to the web every three minutes.
People all over the world view this page, but most importantly, the information is available to the citizens and agencies of Palo Alto, as well as our neighbors.
If you have more questions please contact Public Works Operations 650-496-6974
