Raymond M. Slade, Jr., Certified Professional Hydrologist and Adjunct Professor
Biography: Raymond served as a Hydrologist for 33 years with the U.S. Geological Survey (USGS) in Texas before retiring in 2003. He has authored about 200 reports or presentations on the hydrology and water quality of surface and groundwater in Texas, with emphasis on the Edwards Aquifer, floods, and droughts.
Since his retirement from the USGS he has been an Adjunct Professor and a self-employed Consulting Hydrologist. He is Certified and Registered as a Professional Hydrologist with the American Institute of Hydrology. Raymond is a member of eight water-resource related professional organizations and has served on about 20 committees related to water-resource planning or management.
Key Points of talk: Central Texas often leads the nation in drowning deaths and flood-damage costs—more than 300,000 people reside within the 100-year floodplain in the five-county IH-35 corridor from Williamson to Bexar County. The area is characterized by fast-developing intense storms, some of which have produced world-record rainfall depths. Also, geographic characteristics such as thin soils and steep land slopes contribute substantially to the flooding. However, perhaps the most substantial flooding threat is from easterly moving storms which often follow basin orientation—such storms can overlie and move with channel flooding thus causing immense increases in downstream flood peaks.
Additionally, climate change likely is increasing the flooding threat. For example, trend analyses of data for all long-term NOAA rainfall gages in Central Texas indicate temporal increases in annual-maximum 6-hour storm depths and in annual-maximum 2-day depths during the past 60 years. For example, 23 of the 31 two-day storm depths exceeding 10 inches since 1950 in Central Texas occurred during the second half of the period. Additionally, analysis of data for all 15 long-term streamflow gages in the area document annual-peak discharges to have increased by a mean value of 72 percent during the past 60 years--the 16 largest gaged peaks occurred in the second half of the period. Finally, based on the trend analyses, the flooding threat in Central Texas is expected to increase even more in the future.
