WARNING SYSTEM FOR MONITORING THE TIXTLA LAGOON OVERFLOW

The municipality of Tixtla (Guerrero, Mexico) presents a mean annual precipitation of near 900 mm, frequently affected by inundations caused by meteorological phenomena. In 1989, 2005 and 2013, these suffered severe damage within the population and growing areas. The recent inundation is product of the simultaneous formation of "Manuel" tropical storm (Pacific) and "Ingrid" hurricane (Mexican Gulf) keeping the urban zone flooded over 30 days (0.5 to 3.0 m), causing several adobe houses collapse and material damages to furniture and agricultural areas. The current municipal administration, through the Directorate Civil Protection (DCP) monitors critical areas subject to flooding, in the absence of simple tools or theoretical.-hydrological foundations for accurately accomplishing such surveillance. This study develops a warning system which allows the Civil Protection Municipality personnel to monitor the lagoon overflow, setting in motion immediate actions for protecting the population life and goods. Watch Flood Tixtla (WFT) considers three aspects: operative staff is not informed about hydrologic aspects, the Tixtla lagoon watershed has no hydrometric gauging stations and it must be simple and practical. WFT system brings together the rainfall-runoff process. The hyetograph of at least five days of rain and the lagoon initial level of water are found within the main entrances. The main exit is represented by the level reached after routing the flood through the reservoir and corresponding volume, and by the elevation-duration relationship (graphically). The urban zone begins with a 1335 masl elevation. The critical months of rain are from July to October; the system begins its application and validation during August, September and October 2014 showing acceptable results. The system has been presented and transferred to the Civil Protection personnel for its use in the next rainy season (2015). DCP must inform the population which might take action during prevention, response and recovery stages.