Community Collaborative Rain, Hail & Snow Network (CoCoRaHS) civilian volunteer Michael Chance made a startling discovery when he checked his official CoCoRaHS rain gage after the May 11-12 rainfall event and found it near the rim. The rain gage registered 11.19 inches – the fourth highest report submitted this year to the CoCoRaHS network.

“I was surprised at that amount - we’ve had some heavy rains,” said Chance, who lives in the Pecan Grove neighborhood in Fort Bend County and has a gage in his back yard. “When I first looked at it, it looked like there wasn’t any water in it. But it was almost to the very top if it. I have never seen it that high before.”

CoCoRaHS is a non-profit, community-based network of volunteers of all ages and backgrounds working together to measure and map precipitation (rain, hail and snow). Volunteers take precipitation measurements each day at approximately the same time and then record those measurements on the CoCoRaHS website (www.cocorahs.org) in order to help weather experts keep track of where and how much it rains across the United States. The Harris County Flood Control District relies on precipitation data collected by CoCoRaHS during and after rainfall and flood events and encourages residents in the Houston/Galveston region to be “data collectors” in their own back yards. 

Radar and reports from the Flood Control District’s Flood Warning System (131 strategically-placed gages that measure and electronically report in real time rainfall amounts and water levels in bayous -- www.harriscountyfws.org) and from Sugar Land indicate that on May 11-12, approximately 8-10 inches of rain fell over central Fort Bend County from north of Beasley to Sugar Land. Approximately 4-7 inches fell over southern Harris County from Friendswood to Missouri City. The result was extensive and widespread flooding over much of Fort Bend and south/southwest Harris counties.

“Even with the Flood Control District’s extensive network of gages, the data provided by the CoCoRaHS volunteer network is extremely helpful in compiling data,” said Heather Saucier, Flood Control District spokeswoman.

Fort Bend County has only one automated reporting site at the Sugar Land airport (8.25 inches was recorded after the May 11-12 rainfall event). It is common in this region for thunderstorms to produce small, localized and intense rainfall events that cover only a few miles in size. For example, during the May 11-12 storm, other CoCoRaHS sites located within 5 miles of the Pecan Grove station only recorded 4-5 inches of rain.

“The CoCoRaHS data are critical for showing how much rain fell, especially in cases where the rain is from thunderstorms, and measurements can vary just a few miles apart,” said Dan Reilly, warning coordination meteorologist for the National Weather Service. “The National Weather Service River Forecast Centers use this data in their hydrologic models to make crest forecasts on area rivers and to determine if river flood warnings may be necessary.“

CoCoRaHS data helps fill in the gaps between official rainfall data collection sites in our region, such as the Flood Warning System and the National Weather Service’s climate sites.

Chance is one of several volunteers who record rainfall data in CoCoRaHS’s Houston/Galveston Region (Austin, Brazoria, Chambers, Colorado, Fort Bend, Galveston, Harris, Jackson, Liberty, Matagorda, Montgomery, Polk, San Jacinto, Waller, and Wharton counties). He said he heard about the CoCoRaHS network several years ago through his volunteer efforts with the Texas State Guard and wanted to be a part of the effort.  He signed up to be a volunteer, ordered an official CoCoRaHS rain gage and installed it in a strategic location in his backyard.

“I feel good about volunteering and I like to be able to help where I can,” said Chance, who is a data analyst at Texas Children’s Hospital in the Texas Medical Center. “It doesn’t take a lot of time and it’s a good service that I can provide.”

Data submitted by CoCoRaHS volunteers is organized and displayed on the CoCoRaHS website for the general public’s observation and use. The National Weather Service, meteorologists, hydrologists, emergency managers, public works managers (water supply, water conservation, stormwater), insurance adjusters, the U.S. Department of Agriculture, engineers, mosquito control, ranchers and farmers, teachers and students, and residents utilize the information to do everything from severe storm analysis to comparisons of how much rain fell in neighboring backyards.

In July 1997, a devastating flash flood dumped more than 12 inches of rain on sections of Fort Collins, Colo., resulting in $200 million in damages. In 1998, CoCoRaHS launched at the Colorado Climate Center at Colorado State University with the goal of making improvements in the mapping and reporting of intense storms.

As more volunteers joined the network, rain, hail, and snow maps were produced for storms of all shapes and sizes and the resulting data patterns caught the interest of scientists and the general public. By 2010, CoCoRaHS was a nationwide volunteer network.  CoCoRaHS is supported nationally by the National Oceanic and Atmospheric Administration (NOAA). Partners in Texas include the Office of the State Climatologist (Dr. John Nielsen-Gammon) at Texas A&M University, the Lower Colorado River Authority, and the Department of Geography and the Environment at the University of Texas at Austin, the Harris County Flood Control District, and many other agencies.

To join, go to the CoCoRaHS website (www.cocorahs.org) and click on the “Join CoCoRaHS” emblem in the upper right corner of the homepage. The website also offers a wealth of information on the organization’s background, training and educational tools, where to purchase the required CoCoRaHS rain gage, how and where to set up the gage on your property, and much more.

The Harris County Flood Control District provides flood damage reduction projects that work, with appropriate regard for community and natural values. With more than 1,500 bayous and creeks totaling approximately 2,500 miles in length, the Flood Control District accomplishes its mission by devising flood damage reduction plans, implementing the plans and maintaining the infrastructure. To learn more about the Flood Control District, visit http://www.hcfcd.org.