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Rivers
Term | Definition |
---|---|
Discharge | the volume of water flowing in a river per second, measured in cumecs (m^3/s) |
Precipitation | all forms of moisture that reach the Earth's surface (including rain, snow and dew). |
Evaporation | the transformation of water droplets into water vapour by heating. |
Evapotranspiration | the loss of water from a drainage basin into the atmosphere from the leaves of plants. |
Surface storage | the total volume of water held on the Earth's surface in lakes, ponds and puddles. |
Groundwater storage | the storage of water underground in permeable rock strata. |
Infiltration | the downward movement of water into the soil surface. |
Percolation | the gravity flow of water within soil. |
Overland flow | the movement of water over the surface of the land, usually when the ground is saturated or frozen or when precipitation is too intense for infiltration to occur. |
Throughflow | the movement of water downslope within the soil layer |
Groundwater flow | the deeper movement of water through underlying rock strata |
Dynamic equilibrium | rivers are constantly changing over time to reach a state of balance with their processes that determine their form. As the flows of energy and materials passing through a river system vary, the river changes to move towards this equilibrium. |
Soil moisture | the total amount of water, including the water vapour, in an unsaturated soil. |
Hydrograph | a graph showing for a given point on a stream the discharge, stage (depth), velocity or other property of water with respect to time; a graphical representation of stream discharge (volume/time) during a storm or flood event. |
Flood | a temporary excess of water which spills over onto land. |
Baseflow | water that reaches the channel largely through slow throughflow and from permeable rock below the water table. |
Storm flow | water that reaches the channel largely through runoff. This may be a combination of overland flow and rapid throughflow. |
Hydraulic radius | the ratio of the cross-sectional area of the channel and thelength of its wetted perimeter. |
Wetted perimeter | that portion of the perimeter of a stream channel cross-section that is in contact with the water. |
Cross-sectional area | the total length of the bed and the bank sides in contact with the water in the channel. |
Attrition | the reuction and rounding of particles of sediment carried in water by repeated collision with each other and the banks and bed of the river. |
Abrasion (corrosion) | is the rubbing or scouring of the bed and banks by the sedimentary material carried along the river. |
Corrosion | occurs where rocks dissolve into the water and are carried away. |
Topography | the arrangement of the natural and artificial physical features of an area. |
Simuosity | the curving nature of a meander, described as: actual channel length / straight-line distance. |
Isostatic | changes in sea level resulting from the rise and fall of land masses. |
Eustatic | changes in sea level induced by variations in the amount of water in the oceans. |
Recurrence interval | the interval at which particular levels of flooding will occur. |
Urbanisation | an increase in the proportion of a country's population living in urban areas. It is sometimes used to mean the process of moving from rural to urban areas. |
Frequency | how often floods occur. |
Magnitude | the size of the flood. |
Interception storage | the total volume of water held of the surface of vegetation. |