Publication Date

2012

Document Type

Thesis

Committee Members

Dominic F. David (Committee Member), Mark N. Goltz (Committee Member), Robert W. Ritzi (Advisor)

Degree Name

Master of Science (MS)

Abstract

Hyporheic exchange can be influenced by channel meanders, by streambed topography, and by the heterogeneity within subsurface sediments. Fluvial systems with streambed sediments composed of sandy gravel can be heterogeneous and contain open-framework gravel stratasets that comprise roughly one-third of the sedimentary deposit by volume. The open-framework gravel stratasets have an average lateral length scale on the order of 10 m, average thickness on the order of a decimeter, and an average dip on the order of 10 degrees downstream. The hydraulic conductivity of open-framework gravel stratasets is on the order of 10-1 m/s, and for the larger volume of sandy gravel it is on the order of 10-3 m/s. Connected open-framework gravel stratasets form tortuous higher-permeability pathways throughout the sub-streambed sediment. The results of modeling show that the heterogeneity within the sub-streambed sediment influences the location and magnitude of the interfacial flow (flow across the streambed) more than the effect of meanders, and more than the effect of streambed topography. The heterogeneity gives rise to regions of positive and negative interfacial flow (flow over areas on the order of 50 m by 50 m) scattered across the streambed surface, which are not present in an equivalent but homogeneous system. The heterogeneity also gives rise to interfacial fluxes that are more than an order of magnitude higher than would occur in an equivalent but homogeneous system. These highest-magnitude interfacial flows are typically found at the location of connected open-framework gravel.

Page Count

47

Department or Program

Department of Earth and Environmental Sciences

Year Degree Awarded

2012

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