Enhancing local river flood hazard communication at the Rio Grande Valley

River flooding along the lower Rio Grande reached record to near record levels in middle to late July of 2010, after estimates of more than 127 cm (50 inches) of rain fell across the northern portions of the Sierra Madre Oriental in northeast Mexico, mainly in the states of Nuevo Leon, Coahuila, and Chihuahua, associated with the remnants of Hurricane Alex and Tropical Depression Number Two. Initial heavy rains across mountainous Nuevo Leon produced devastating flash floods in Monterrey; and additional heavy rains produced additional runoff which filled up a network of reservoirs on the lee side of the Sierra Madre in México, and along the lower Rio Grande. Ultimately, the water flowed into a network of floodways in the Lower Rio Grande Valley. Flooding impacted a number of communities along and near the river in Texas and Mexico. The National Weather Service Forecast Office (WFO) in Brownsville, Texas, utilized multiple sources of information to communicate the threat of flooding to locations along the lower Rio Grande. These sources included observed and forecasted river stage levels; near-real time situation reports from towns, cities, and portions of counties impacted by high water; expertise from the U.S. International Boundary and Water Commission, West Gulf River Forecast Center, and WFO Brownsville; photographic and video evidence, and Geo-referenced data. The data was assimilated into a number of information streams including standard NWS River Flood Warning text products, areal-based Hydrologic Flood Advisories for potential flood areas not in or near a river forecast point, near-real time web page news articles and event stories, and routinely updated river-at-a-glance observed and forecast graphics. Several of these information streams were provided in English and in Spanish. The effectiveness of combining multiple data sources into clear, specific messages for a variety of stakeholders will be discussed. Results from conversations with stakeholders will be used to provide a possible framework for location-specific hydrologic messages that incorporate geographic, demographic, and sociological information to further improve how flood threats are communicated to those in harm's way.