INTRODUCTION 



LOCATION AND PHYSIOGRAPHIC FEATURES 



The latitude of San Antonio is 29 degrees north. San An- 

 tonio is about 15 miles southeast of the Balcones Fault Line 

 which divides the Great Plain to the north and west and the 

 Coastal Plain of the south and east. The Edwards Plateau is the 

 southern most Texas division of the Great Plain. San Antonio 

 has an elevation of six to eight hundred feet. 



The Edwards Plateau is characterized by limestone hills 

 and intervening, wide, fertile valleys. The hills range in height 

 from fifty to two hundred feet and are covered with a thin layer 

 of poor dry clay soil. The majority of them are round-topped 

 and have a terraced appearance due to the weathering of the 

 alternating layers of hard and soft rock. Many have their 

 sides broken by steep cliffs and ragged ledges. Short, deep, 

 sharply-cut, rocky ravines break back into these hills and open 

 down into rock-filled creek beds usually dry but with rains 

 sometimes brimful for several days. As these storm waters run 

 away, they leave pools and wet holes in the deeper depressions 

 that offer residence for fish and frogs, and algae for weeks and 

 months. 



The Coastal Plains to the south are marked by rolling hills, 

 much level land, flood plains, and the general absence of ' i float- 

 ing rocks". The soil is much deeper than that of the Edwards 

 Plateau and varies from a brown-gray loam to a reddish or white 

 sand. The subsoil is alluvial gravel and clay and in many places 

 is cut thru, forming steep high bluffs and deep gullies. A very 

 small percentage of this land is under cultivation, the most of it 

 being used as pasture land. 



The Valley of the San Antonio River is drained principally 

 by the San Antonio River and its few small tributaries. This 

 river has its origin in the fissure springs north of Brackenridge 

 Park and is a permanent flowing stream. On either side the 

 course to the southeast is riverbottom land which serves as a 



