Rivers, flood and management – definition

precipitation
all forms of moisture that reach the Earth’s surface
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 volumen 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
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 within the processes that determine their form – as the flows of energy and materials passing through river system vary, river changes moving towards this equilibrium
velocity
speed and the direction at which a body of water moves
erosion
the wearing away of the surface of the land including the breakdown of rock and its removal by wind, water or ice
interception
the prevention of rain from reaching Earth’s surgace by trees or plants
condensation
process by which water vapour is converted into water
channel flow
the movement of water within the river channel
soil moisture
the total amount of water, including water vapour in an unsaturated soil
hydrograph
graph showing for a given point on a stream the discharge, depth, velocity or other property of water with respect to time –

graphical representation of steam during a storm or flood event

flood
a temporary excess of water which supplies 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 run off – may be a combination of overland flow and rapid throughflow
hydraulic radius
the ratio of the CSA of the channel and the length of its wetted perimeter
wetted perimeter
that portion of the perimeter of a steam channel cross section that is in contact with the water
CSA
total length of the bed and the bank sides in contact with the water in the channel
attrition
reduction and rounding of particles of sediment carried in water by repeated collision with each other and the banks and bed of the river
abrasion
is the rubbing or scouring of the bed and banks by the sedimentary material carried along the river
corrosion
occurs when rocks dissolve into the water and are carried away
topography
the arrangement of the natural and physical features of an area
sinuosity
the curving nature of a meander – described as

actual channel length/straight line distance

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 – 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 on the surface of vegetation