Experimental Study of Drainage Basin Evolution and Its Hydrologic Implications.

摘要

An experimental study was undertaken to document the evolution of a drainage basin and to identify hydrologic changes. A 9 by 15 m facility was built and filled with a homogeneous mixture of sand, silt, and clay. A sprinkling system was established along the sides of the container, and it provided four intensities of rainfall to the nearly 140 sq. m drainage basin. Two experiments were performed each of which documented the evolution of the drainage system on gently sloping surfaces. The initial conditions (relief and initial surface slope) of each experiment were different, and these initiated differences in the mode of network growth. Nevertheless, during both experiments drainage patterns evolved through the sequence of network initiation, extension of the network to maximum extension, and, finally, to abstraction. Sediment yields from the basin undergoing erosional evolution show an exponential decline with time. This overall trend is characterized by high variability. Hydrographs generated as basin evolution progressed suggest that runoff produced by lower precipitation intensities is most influenced by the geomorphology of the basin. The ratio of peak discharge to the equilibrium discharge shows a dramatic increase during early basin development. The efficiency of the hydrologic response, appears to increase to a maximum as drainage density and/or relief increases. Further increases in drainage density do not increase the efficiency of the hydrologic system. (Author)