Glossary of Hydrology and River Sciences, Quizzes of Geography

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TERM 1 Stream discharge DEFINITION 1 Streamflow volume past a point in a given unit of time TERM 2 Fluvial DEFINITION 2 Having to do with river TERM 3 Erosion DEFINITION 3 Denudation by wind, water, or ice, which dislodges, dissolves, or removes surface material TERM 4 Transport DEFINITION 4 The actual movement of weathered and eroded materials by air, water, and ice TERM 5 Deposition DEFINITION 5 The process whereby weathered, wasted, and transported sediments are laid down by air, water, and ice TERM 6 Alluvium DEFINITION 6 General term for the clay, silt, sand, gravel, and mineral fragments deposited by running water as sorted or semi- sorted sediment on a floodplain, delta, or streambed TERM 7 Base level DEFINITION 7 Level below which a stream cannot erode its valley TERM 8 Drainage basin DEFINITION 8 The basic spatial geomorphic unit of a river system; distinguished from a neighboring basin by ridges and highlands that form divides, marking the limits of the catchment area of the drainage basin TERM 9 Sheetflow DEFINITION 9 Surface water that moves downslope in a thin film as overland flow, not concentrated in channels larger than rills TERM 10 Continental divide DEFINITION 10 High drainage divide, usually an extensive mountain range or highland region TERM 21 Exotic stream DEFINITION 21 River that rises in a humid region and flows through an arid region, with discharge decreasing toward the mouth; ex- Nile and Colorado Rivers TERM 22 Hydraulic action DEFINITION 22 Work of water flowing alone TERM 23 Abrasion DEFINITION 23 Mechanical wearing and erosion of bedrock accomplished by the rolling and grinding of particles and rocks carried in a stream, removed by wind in a "sandblasting" action, or imbedded in glacial ice TERM 24 Competence DEFINITION 24 A stream's ability to move particles of a specific size TERM 25 Dissolved load DEFINITION 25 Materials carried in chemical solution in a stream, derived from minerals such as limestone and dolomite, or from soluble salts TERM 26 Suspended load DEFINITION 26 Fine particles held in suspension in a stream. The finest particles are not deposited until the stream velocity nears zero TERM 27 Bed load DEFINITION 27 Coarse materials that are dragged along the bed of a stream by traction or by the rolling and bouncing motion of saltation; involves particles too large to remain in suspense TERM 28 Traction DEFINITION 28 A type of sediment transport that drags coarser materials along the bed of a stream TERM 29 Saltation DEFINITION 29 The transport of sand grains by wind or stream, bouncing the grains along the ground in asymmetrical paths TERM 30 Aggradation DEFINITION 30 The general building of land surface because of deposition of material; opposite of degradation. When the sediment load of a stream exceeds the stream's capacity to carry it, the stream channel becomes filled through this process TERM 31 Braided stream DEFINITION 31 A stream that becomes a maze of interconnected channels laced with excess sediment. Braiding often occurs with a reduction of discharge that reduces a stream's transporting ability or with an increase in sediment load TERM 32 PRECIP DEFINITION 32 Precipitation Input. Moisture supply to Earth's surface TERM 33 ACTET DEFINITION 33 Actual Evapotransportation. Evaporation and transpiration combined TERM 34 Evaporation DEFINITION 34 The net movement of free water molecules away from a wet surface into air that is less than saturated TERM 35 Transpiration DEFINITION 35 Cooling mechanism in plants where it moves water through small openings in the leaves, and as the water evaporates the plant cools (like humans sweating) TERM 46 Available water DEFINITION 46 Most capillary water that remains in the soil TERM 47 Field capacity DEFINITION 47 Storage capacity for for plants TERM 48 Gravitational water DEFINITION 48 When soil becomes saturated after a precipitation event, any water surplus in the soil body TERM 49 Soil-moisture utilization DEFINITION 49 The extraction of soil moisture by plants for their needs; efficiency of withdrawal decreases as the soil storage is reduced TERM 50 Soil-moisture recharge DEFINITION 50 Watering entering available soil storage spaces TERM 51 Porosity DEFINITION 51 The texture and the structure of the soil dictate available pore spaces TERM 52 Permeability DEFINITION 52 Property of the soil that determines the rate of soil-moisture recharge TERM 53 Drought DEFINITION 53 No precise definition, but the water-resource demand is not met due to a lack of water. Can be meteorological (dry conditions + lower precipitation + higher temperatures = soil moisture), agricultural (changes soil moisture and weather elements affect crop yields), hydrologic (reservoir levels decrease, streamflow decreases and groundwater mining increases), and/or socioeconomic (water loss leading to loss of life. TERM 54 Groundwater DEFINITION 54 Water beneath the surface that is beyond the soil root zone; a major source of potable water TERM 55 Zone of aeration DEFINITION 55 Where soil and rock are less than saturated (some pore spaces contain air) TERM 56 Zone of saturation DEFINITION 56 Area where subsurfacewater accumulates. Pores are completely filled with water like a hard sponge TERM 57 Aquifer DEFINITION 57 Rock layer that is permeable to groundwater flow adequate for wells and springs TERM 58 Aquiclude DEFINITION 58 Body of rock that does not conduct water in usable amounts TERM 59 Water table DEFINITION 59 Upper limit of the water that collects in the zone of saturation TERM 60 Confined aquifer DEFINITION 60 Bounded above and below by impermeable layers of rock or sediment TERM 71 Undercut bank DEFINITION 71 Outer portion of a meandering stream. Subject to the fastest water velocity and therefore most eroded part. TERM 72 Point bar DEFINITION 72 Inner portion of a meandering stream. Experiences the slowest water velocity and thus receives sediment fill. TERM 73 Oxbow lake DEFINITION 73 When part of a meander stream becomes isolated from the rest of the river, it is this TERM 74 Gradient DEFINITION 74 Rate of elevation decline from a river's headwaters to its mouth TERM 75 Graded stream DEFINITION 75 A stream that, over a number of years, adjusts to provide just the velocity required for transportation of the load supplied from the drainage basin TERM 76 Profile of equilibrium DEFINITION 76 Longitudinal profile of a graded stream TERM 77 Nickpoint DEFINITION 77 Point of interruption in the longitudinal profile of a stream (i.e. a waterfall or an area of rapids) TERM 78 Functional Model of Dynamic Equilibrium DEFINITION 78 Emphasizes the effects of individual processes interacting on streams and hillslope systems TERM 79 Morris Davis DEFINITION 79 Proposed the idea of stream "ages"- youth, maturity, and old age TERM 80 Floodplain DEFINITION 80 Flat, low-lying area flanking many stream channels that is subjected to recurrent flooding TERM 81 Natural levees DEFINITION 81 Long, low ridge that forms on both sides of a stream in a developed floodplain. Depositional products of river flooding TERM 82 Yazoo tributary DEFINITION 82 River prevented from joining the main channel by natural levees and the elevated channel of the river. Flows parallel to the river and through the backswamp area TERM 83 Backswamp DEFINITION 83 A low-lying, swampy area of a floodplain, adjacent to a river, with the river's natural levee on one side and higher topography on the other TERM 84 Alluvial terraces DEFINITION 84 Level areas that appear as topographic steps above a stream, created by the stream as it scours with renewed downcutting into its floodplain; composed of unconsolidated alluvium TERM 85 Delta DEFINITION 85 Level (or nearly so) depositional plain that forms at the mouth of a river