On the basis of the Manning equation and basic mass conservation principles, we derive an expression for scaling the steadystate width (W) of river channels as a function of discharge (Q), channel slope (S), roughness (n), and width-to-depth ratio (!): W " [!(! # 2)2/3]3/8Q3/8S$3/16n3/8. We propose that channel width-todepth ratio, in addition to roughness, is a function of the material in whic...

Accelerated loss of ice from Greenland and Antarctica has been observed in recent decades. The melting of polar ice sheets and mountain glaciers has a considerable influence on sea level rise in a changing climate. Ice thickness is a key factor in making predictions about the future of massive ice reservoirs. The ice thickness can be estimated by calculating the exact location of the ice surfac...

The significance of stochasticity in the characteristics of the surface layers of a site to the resulting spatial variation of seismic ground motions and the seismic ground strains is investigated. For this purpose, an analytical site-specific model is developed. The model approximates the site topography by a horizontally extended layer with random characteristics overlying a half-space (bedro...

[1] Tracer buoyancy has been shown to influence breakthrough from two-well tracer experiments conducted in porous media. Two-well tracer experiments are presented from fractured crystalline bedrock, in which the specific gravity of the tracer injectate varied from 1.0002 to 1.0133. Under the forced hydraulic conditions imposed, no difference in breakthrough was noted for the three experiments. ...

i Preface iii Summary v Introduction 1 Measurement techniques employed 3 Ground 3 Airborne 3 Magnetometer survey 4 Results 4 Ground control study 4 VLF survey 8 Bedrock geology and resistivity 8 Aeromagnetic survey results 13 Conclusions 13 Literature cited 13 Appendix A. Theory of electromagnetic resistivity si rveying 15 Appendix B. Magnetic surveying 19

Did you know that the earth beneath your feet is teeming with life? Imagine yourself standing outside. If you started digging, at some point beneath the soil you would eventually hit hard rock—that is the bedrock forming the Earth’s crust. Even this seemingly solid material has cracks and pores that contain groundwater (water that is held in the ground), and where there is water, there can be l...

Introduction The Potomac Formation is a heterogeneous assemblage of ancient river deposits consisting chiefly of unconsolidated and poorly consolidated sands, silts, clays, and small amounts of gravel, along with localized zones of diamictons of uncertain origin. It is the dominant geologic unit in the City of Alexandria. It crops out or is close to the surface everywhere west of Old Town and D...