Document Type

Dissertation

Date of Award

1974

Keywords

Geomorphology, Pennsylvania, Hydrogeology, Groundwater

Degree Name

Doctor of Philosophy (PhD)

Department

Geological Sciences

First Advisor

Donald R. Coates

Second Advisor

Marie E. Morisawa

Third Advisor

James R. Beerbower

Abstract

Eight watersheds in Pennsylvania, draining areas of uniform climate and lithology, but different geologic structure, were studied for their geomorphic, geologic, hydraulic, and hydrologic characteristics.

Low streamflow characteristics, defined by base-flow recession curves, and streamflow duration, for 25 summer months, show that streams in the folded and faulted Valley and Ridge province have stronger base-flow regimes than those in the relatively undeformed Appalachian Plateau.

The separate effects of geologic structure and lithology on groundwater regimes can be evaluated quantitatively on the basis of a single geomorphic parameter, the hypsometric integral. In the study area the integral is seen to be an index of the areal distribution of different rock types, and can be mechanistically related to the physical laws which govern groundwater movement. Low flow discharge increases as the value of the integral increases. This is viewed as a lithologic control. Also, a predominantly siltstone-shale section in the deformed terrane produces as much low flow runoff per unit area as a predominantly sandstone section in the plateau terrane. Because these two lithologies should produce significantly different quantities of base flow, their hydrologic similarity is viewed as being caused by structural control.

Longitudinal profiles of the streams are related to basin lithology, structure, and depositional features of tributary streams. The shape of channel materials is related to the sedimentary structure of parent materials, and channel cross sections are related to present climates. Hydraulic geometry of the streams indicate that hydraulic performance is related to low streamflow characteristics.

Experimental data was obtained from watershed models that were built and designed to reflect the effect of structural control as revealed by basin shapes and tributary distribution and orientation. Analysis of these data indicate that the degree of basin eccentricity is an important consideration that determines characteristics of peak flow and recession curves when used to evaluate different configurations within families of generalized shapes.

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