a\<- 



133 



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unfenced tract adjacent to the South tract on the east side of the Laurel- 

 Bowie road, and that part of the refuge in Anne Arundel County are not 

 covered in this study. 



Topography and Water Supply 



The refuge is situated entirely within the watershed of the Patuxent 

 Fdver, which here flows through a valley the maximum dimensions of which 

 are about 3 miles wide and 150 feet deep. The altitude of the area varies 

 fron less than 80 feet above sea level along the river to mere than 220 

 feet near the west ana south ends, "but the slopes are mostly gentle, ex- 

 cept for frequent 5- to 15-foot bluffs along the highland side of the bot- 

 toms. The river falls 20 to 25 feet in its rather crooked course through 

 a part of the refuge, traversing for the entire distance a bottom land 

 that, on the southwest side of the river, except at one place, is a quar- 

 ter to half a mile wide. In places, between the bottoms and the upland 

 slopes, are broad, nearly level terraces that lie only a few feet above 

 the bottoms. 



Several brocks rise just outside the boundary of the refuge and flow 

 more or less directly toward the river. They are so small that the ma- 

 jority do not maintain channels across the bottom land, but spread out or 

 disappear on broad, flat areas or lose their identity in high-water chan- 

 nels along the highland side of the bottoms. One and one-half miles is 

 the greatest length of any brook except the southeasternmost, Cash Branch, 

 which drains the south tract and has a length of over 3 miles. Its lower 

 course is outside the refuge boundary. Cash Branch ha.s been dammed to 

 form 2 lakes in the south tract. In most years, the bottom lands are 

 flooded on one or more occasions for a few days at a time, but the river 

 normally flows between well-defined banks. A small flow of water continues 

 through a few shallow side channels, except in summer; and in places along 

 the highland side of the bottoms there are permanent swampy areas. The 

 deepest and largest of these, which is more of a peat bog than a river 

 swamp, lies just southwest of Duvall Bridge. A few springs occur along the 

 bottom-land bluffs and elsewhere. 



Geology and Soils 



The refuse is only a few miles from the inner boundary of the Atlan- 

 tic Coastal Plain, which follows a northeast-southwest lino in the vicin- 

 ity of Laurel. Underlying strata are all unconsolidated sediments of Cre- 

 taceous age. 



The soils have developed mostly from weathered Coastal Plain rocks. 

 An exception is the Congaree silt loam (See 1925 Soil Survey of Prince 

 Georges County, Md. ) , which covers the Patuxent bottom land but which has 

 been washed there from the Piedmont Plateau. This loam is potentially 

 one of the most productive of soils. Its origin partially accounts for 

 this ani for the fact that on the better drained parts of the bottom land 

 many "rich woods" species of herbaceous flowering plants occur that are 

 characteristic of the Piedmont Plateau and that have not been discovered 



