The amount of rain Tennessee recieved in a two day period more than doubled that in the historical record.
Now if you wish to discuss geological records, take a look at the Karoo Formation in South Africa, and what happened there at the P-T event. Former serpentine river channels that laid down silt and clay fines suddenly changed to braided river channels with cobbles and boulders.
Methane Catastrophe
More water vapor in the atmosphere, however, would have meant more precipitation, and this precipitation would have come in the form of more severe storms. Some continental areas therefore may have been subject to a kind of double whammy: drying out more because of increased evaporation, and then periodically getting hit by powerful storms. This is a prescription for drought punctuated by flash floods and rapid erosion, and would have imposed difficult living conditions on the many of the creatures of the affected areas. Other areas simply received more precipitation, which ameliorated harsher climates and made arid climates less so (Retallack, 2003).
In South Africa's Karroo Basin, the additional precipitation may have been responsible for changing river dynamics and altering meadering rivers (which sweep in great curves across their valleys) to braided rivers (which are comprised of many interwoven strands). Although numerous factors control the specific shapes of rivers, the amount of flow is an important one, and braided rivers tend to indicate higher flow rates than meandering ones. The major extinction of terrestrial plants, whose root systems tend to anchor soils, is also a likely factor in altering river shape (Ward, 2000).
