Brazos and Colorado Rivers Delta System
Over the past 20,000 years, the Brazos and Colorado Rivers deposited large volumes of sediment, which filled the valleys and prevented the 400 foot rise in sea level from flooding these river valleys. The San Jacinto and Trinity River systems of Galveston Bay and the Lavaca River system of Matagorda Bay delivered smaller volumes of sediment, allowing these river valleys to be flooded due to rapidly rising sea level. (The Lower Colorado shifted its course to the present-day channel less than a few hundred years ago - Van Sicien, 1961).