1. TEXAS COASTAL WETLANDS Surface Water and its link to coastal wetlands loss Christine Otto

2. BACKGROUND §Texas wetlands § 7.6 million acres of wetlands in Texas § Between mid 1950’s and 1979, 35% loss §Link of wetland loss to population growth and density § Between 1960 and 1990, population along coast more than doubled § 187 persons/mile squared

3. URBAN DEVELOPMENT Alteration of wetland hydrology, topography, and vegetation

4. URBANIZATION INCREASED IMPERVIOUS SURFACE RUNOFF (more and faster) DECREASE GW RECHARGE EROSION REDUCED FLOWS IN WETLANDS

5. OBJECTIVE §Incorporate the use of GIS in an analysis of the wetland loss along the Texas Coast §Determine if a correlation exists between the decline in wetlands and the urban growth in the Texas Coastal Area

6. DATA SOURCES §Texas WetNet (General Land Office): Wetland Files, Texas Coastal Boundary §Dr. David Maidment’s CE394K.3 class folder: §huc12 - polygon theme of Hydrologic Cataloging Units for Region 12 of the US §rf1huc12 - EPA River Reach files for Region 12 §Texasppt - grid of mean and annual precipitation over Texas (mm) §Texas USGS database: Texas Discharge Data §ESRI: Urban development along coast

7. §Classify huc12.shp theme based on HUC codes (4 subbasins) METHODOLOGY 120402 120904 121004 121102

8. METHODOLOGY §Classify huc12.shp theme based on HUC codes (4 subbasins) §Selected features of other themes within area of extent

9. METHODOLOGY §Classify huc12.shp theme based on HUC codes (4 subbasins) §Selected features of other themes within area of extent §Calculate Precipitation, Runoff, and Flow Grids

10. METHODOLOGY: Precipitation Balance of I and O = water budget Natural Water Level Fluctuations Hydroperiod

11. METHODOLOGY: Runoff Wetland Response Time Change in water levels Change in detention time R (mm/yr) = 0.51 * P (mm/yr) - 339

12. METHODOLOGY §Classify huc12.shp theme based on HUC codes (4 subbasins) §Selected features of other themes within area of extent §Calculate Precipitation, Runoff, and Flow Grids §Discharge Data compiled and graphed

13. FLOW 90% loss Submerged marine grasses in Galveston

14. AREA OF INTEREST 9,563 acres lost along upper coast

15. TIDAL INFLUENCES Salt water intrusion Erosion

16. CONCLUSION §Correlation between urban growth and wetlands loss along Texas Coastal Boundary §Too early to determine long-term impacts §Many factors affecting loss; difficult to delineate exact causes

17. FUTURE WORK §Determine areas of loss versus areas of conversion §Compare data found with USGS and Texas General Land Office’s findings § EPA’s Dallas Office: Trinity River Basin and Galveston Bay