Flooded Bays? Rice Prof Says It's Happening
Thursday, January 4, 2007
By: Jack Williams

A Rice University researcher says upstream, man-made dams and rising seas could lead to significant bay flooding along the Gulf Coast, including Galveston Bay. As Houston Public Radio's Jack Williams reports, professor John Anderson warns the bay changes could come sooner rather than later.

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"We're not talking something here that potentially will happen in 100 or 200 years. We're talking something that could well happen in a matter of decades, changes that could happen in a matter of decades."

Anderson has spent years researching flooding trends along the Gulf Coast and says it's not unusual to have bay flooding events every 1500 years or so, cyclical occurances that result from the combination of slowly rising sea levels and less river-borne sediment flowing into the bays.

"The human influence of putting dams on rivers is equivalent if not greater than some of these natural climate events in terms of how they impact sediment supply from the river to the bay. So as sea level goes up, unless there's enough sediment coming into the bay to keep up with the rate of rise, then you will flood the bay. In other words water depths will increase, wetlands will be lost or at least will shift from their location, and there's going to be an impact from that."

Anderson and his research colleagues have analyzed sediment core samples from Galveston, Corpus Christi and Matagorda bays and several lakes in Louisiana where flooding events have happened in the past and says the decrease in the amount of sediment seems to be the common factor. He says the changes in the bays can be rapid.

"What we basically discovered is that rather than just slowly change as sea level rises due to the flooding that takes place, inundation of the bays, rather than change slowly, they have threshholds and they are able to maintain the setting at certain sea level rise and sediment input, but when there's an imbalance in that supply or sea level rise, the systems respond rather radically."

The most obvious potential problems that arise from bay flooding include the eventual disruption or complete destruction of business or residential developments along bays in Texas and elsewhere. Anderson says getting river sediment past the dams and into the bays is one solution.

"In other words, engineering that would basically pump the sediment or move the sediment through the system to keep it moving in through the system. There are ways to engineer around a lot of these problems. Until we undertand the magnitude of the problem given the cost of the remedies, it's not likely that anything is going to be done."

Based on sedimentary records, researchers say the world's oceans are rising more quickly, 5 millimeters a year now compared to 2 millimeters a year recorded throughout most of the 20th century.