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Published byDiane Kelley Modified over 9 years ago
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TEXAS COASTAL WETLANDS Surface Water and its link to coastal wetlands loss Christine Otto
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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
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URBAN DEVELOPMENT Alteration of wetland hydrology, topography, and vegetation
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URBANIZATION INCREASED IMPERVIOUS SURFACE RUNOFF (more and faster) DECREASE GW RECHARGE EROSION REDUCED FLOWS IN WETLANDS
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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
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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
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§Classify huc12.shp theme based on HUC codes (4 subbasins) METHODOLOGY 120402 120904 121004 121102
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METHODOLOGY §Classify huc12.shp theme based on HUC codes (4 subbasins) §Selected features of other themes within area of extent
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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
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METHODOLOGY: Precipitation Balance of I and O = water budget Natural Water Level Fluctuations Hydroperiod
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METHODOLOGY: Runoff Wetland Response Time Change in water levels Change in detention time R (mm/yr) = 0.51 * P (mm/yr) - 339
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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
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FLOW 90% loss Submerged marine grasses in Galveston
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AREA OF INTEREST 9,563 acres lost along upper coast
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TIDAL INFLUENCES Salt water intrusion Erosion
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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
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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
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