MIGRATION RATES AND STORM IMPACTS ON DUNES IN SOUTHEAST TEXAS, LANDWARD SIDE OF THE LAGUNA MADRE

Coastal sand dunes are an important feature acting as a barrier from high energy storms and shielding inland areas from damaging forces of wind and waves. Sand dunes develop under a range of climatic and environmental factors. Any change in dune morphology can indicate variations in wind velocity and direction. They receive their supply of sand from adjacent beaches, so changes in sea level and near shore conditions are essential factors. They have the ability to migrate as fast as 10-20 meters a year to engulf entire fields. Satellite imagery was utilized to gather data to analyze, observe, and calculate the changes in dimension of dunes on the landward side of Laguna Madre, southeast Texas. Various satellite data were also analyzed to calculate the rate of migration of dunes over a twenty-one year time span. Tools within Google Earth Pro ©, such as historical imagery, place mark, ruler, and polygon, were utilized to analyze images of dune fields from 1995 to 2016. The study area was subdivided into three sections. In each section, the dimensions of dunes were measured and the migration rate was calculated using the formula: Rate = Distance/Time (R=d/t). A total of 91 dunes were studied, and the average migration rate for time frames 1995-2003, 2003-2009, and 2009-2016 were calculated. The resulting numbers were combined for a comparative analysis for each of the sections. It was noted that each section had peak migration rate in 1995-2003, migrating at average rates from 17.4 meters per year to 19.3 meters per year. An overall decreasing trend in migration rates during 2003-2016 was revealed from the comparative analysis. An examination of weather conditions of the study area within 1995-2003 revealed the tracks of two tropical storms, and one major hurricane coming close enough to impact the study area. Further research will involve the use of SPOT and MODIS to specifically identify the impact zones of those storms and assess the effect on dune migration in the region.