When unusually large amounts of collected water build-up along a watercourse, flooding occurs. The land areas adjacent to the streams, rivers, lakes and oceans that are inundated when flooding occurs are floodplains. Under purely natural conditions, this flooding causes little or no damage.
Damage does occur, however, when man attempts to occupy the flood-plain.
There are approximately 80,000 miles of river and streams throughout the State of Texas. Historically, these watercourses have served as focal points for the establishment and growth of cities and towns by providing needed water resources and vital transportation corridors. Along with the benefits of locating next to rivers and streams, however, there is also a certain danger. Triggered by heavy or prolonged rainfall, rivers and streams periodically overtop their banks, spreading floodwaters onto adjacent low-lands or floodplains. Floods are by the most common and serious natural hazard with which Texas municipalities must contend.