WSPC07406 - Laserfiche WebLink

Home Browse Search

0015G8 30.5--2 WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK Degradation. The geologic process by which stream beds, floodplains. and the bottoms of other water bodies are lowered in elevation by the removal by water of material from the boundary. Deposition. The mechanical or chemical process through which sediments accumulate in a resting place. Drawdown. The difference between the flood elevation recorded at a stream gage and the actual flood elevation which is caused by the effects of high velocity on the gage. As used in the 'procedure' - the lowering of a water level, as for example. depth to groundwater, lake level, or stream stage. Equilibrium. (Or dynamic equilibrium). The condition of a stream where a reach is neither aggrading nor degrading and can be represented by the qualitative relationShip Osd - OwS where Os = sediment discharge, Ow = water discharge, d = sediment particle size. and S represents slope. Erodible Bed/Bank Channels. Those natural, perennial, alluvial. and fluvial stream channels or channel reaches which are free to adjust their dimensions, shape, pattern, or gradient in response to changes in s treamfl ow. Flood Elevation. given recurrence the level of the The height above the thalweg at which a discharge of a interval flows. Most commonly applied to heights above banks of the active channel. Flow-Duration Curve. A graphical plotting of magnitudes of stream diSCharge (ordinate axis) against the percent of time each magnitude is equaled or exceeded (abscissa axis). Geomorphology. That branch of both physiography and geology which deals with the form of the earth, the general configuration of its surface. and the changes that take place in the evolution of landforms. Hydrograph. A graph showing stage, discharge. velOCity. or other properties of water flow with respect to time. When the discharge is shown against time, the graph is a discharge hydrograph, or commonly called simply a hydrograph. Inner Berm. Equivalent to the "depositional-bar level" described as a longitudinal. in-channel feature formed along the borders of a stream channel at a stage of the flow regime when the local competence of the stream is incapable of moving the sediment particles on the submerged surface of the bar. Non-Erodible Channels. Those stream channels or channel reaches in which the materlal forming the bed and banks determines the morphology of the channel rather than the force of moving water.