Because of its location, the Aransas Refuge is vulnerable to the sporadic 

 hurricanes (and associated tornadoes) which typically frequent the gulf coast 

 during late summer and fall. Storm-associated damages result from the effects 

 of high-velocity winds and/or flooding. Water damage is caused by abnormally 

 high tides preceding the storm and/or flooding resulting from accompanying 

 heavy rains. The barrier islands (St. Joseph and Matatorda Islands) moderate 

 the storm effects and thus offer significant protection. 



Hydrology . The Ingleside barrier complex, which was deposited on top of 

 impermeable clays of a preceding geologic period, lies beneath the Aransas 

 Refuge. Underlying these impermeable clays is the gulf coast aquifer, a series 

 of interconnected lenses and fingers of sands, silts, and clays. The source 

 of water for the shallow (17 m, or 56 ft) surface unit is direct percolation 

 of rainwater through the overlying sands. This water is slightly saline to 

 saline due to saltwater seepage and leaching of wind-borne surface salts. The 

 strata comprising the Gulf Coast aquifer slope seaward (0.5 to 0.8 m per km, 

 or 1 to 1.5 ft per mi), and groundwater in this aquifer thus occurs under 

 artesian flow conditions. Groundwater is recharged inland where the units 

 outcrop (Bernard and LeBlanc, 1965). 



The relatively low surface relief and the rapid permeability of the sandy 

 substrate discourage the formation of extensive surface drainage features, 

 "xisting drainage is generally to the south and southwest via small creeks and 

 groundwater. Burgentine, Twin, and Salt Creeks discharge into northern St. 

 Charles Bay after collecting surface runoff from the less permeable soils of 

 higher clay and silt content. No major rivers pass through the refuge, nor do 

 any major creeks flow across the deep sand substrate of the peninsula. Soil 

 erosion is not a problem. 



Low-lying areas of the uplands commonly form wetlands varying from slightly 

 wet depressions to deeper ponds and sloughs. There can be considerable annual 

 variation in the areal coverage of these sites, depending on topography, degree 

 of soil saturation, and annual precipitation. The largest body of standing 

 water in the refuge uplands, Burgentine Lake, was created by the impoundment 

 of Burgentine Creek. 



Saltwater flooding associated with hurricane tidal surges can be expected 

 to affect uplands below the 3-m (10-ft) contour. However, much of the land 

 below an elevation of 6,1 m (20 ft) may be flooded locally when maximum storm- 

 surge conditions are focused on this specific section of the shoreline. Inland 

 freshwater flooding will result from stream flooding and hurricane-aftermath 

 rainfall (Brown et al., 1974). 



Vegetation . The Aransas Refuge lies in the Gulf Prairies and Marshes vege- 

 tational area of Texas (Gould, 1969). Site elevation, proximity to salt water, 

 and fire frequency are the chief factors regulating the vegetation of the refuge. 

 Upland terrestrial communities have been catagorized by various authors as con- 

 sisting of several vegetation types: oak thickets or mottes, oak brush, 

 savannahs, and meadows or grass-sedge flats. (Halloran, 1943; Blakey, 1947; 

 White, 1973; Springer, 1975). 



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