Hydrology and Fluvial Geomorphology Flashcards
Stem flow
water running down a plant stem or the trunk of a tree
Soil moisture
water stored in the soil
Transpiration
a process by which plants return moisture to the atmosphere, having taken it up though their roots
Groundwater store
a store of water held below the surface in the ground zone, above the base rock
Surface store
water held on the surface in lakes, ponds and puddles
Interception
where some precipitation is temporarily caught by plant leaves before reaching the ground
Groundwater flow
the down slope movement of water through underlying rocks or the downhill transfer of water through pores and small cavities in the soil/ rock, depending on the rock type
Aquifer
an underground layer of permeable rock, sediment or soil that yields water
Throughfall
water falls off leaves onto the ground surface, or falls through gaps in the vegetation
Field capacity
the amount of water that the soil is able to hold when it is fully saturated
Catchment area
the area within a drainage basin
PEVT
the water loss that would occur if there was an unlimited supply of water in the soil for use by vegetation
Interception loss
water retained by plant or or surfaces that is later absorbed or evaporated
Soil moisture deficit
the degree to which the soil moisture levels fall below field capacity
Soil moisture recharge
precipitation exceeds PEVT, so there is some filling up of water in the dried-up pores
Soil moisture utalisation
water is drawn to the surface by capillary action
Porosity
the capability of the rock to hold water
river rejuvenation
a period of vertical erosion to achieve a new, lower base level, enabling the river to achieve its desired concave shape
eustatic change
global rise and fall of sea levels
isostatic change
the local adjustment of land levels
river capture
when a river cuts backwards over time due to head ward erosion and captures tributaries of another river
alluvium deposition
sediment that is deposited that was once suspended
river regime
hydrograph showing river discharge over a year
drainage density
number of tributaries per km2
bankfull discharge
maximum discharge a river can hold before it goes into flood
saturated overland flow
soil has reached field capacity so no more water can be absorbed resulting in overland flow
hortonian flow
when the ground is hard after a period of dry weather, so infiltration cannot take place, resulting in overland flow
clear-water erosion
erosion caused by the action of the water
antecedent rainfall
rainfall that has occurred previous to a weather event
alluvial fan
triangular shaped deposits of water-transported material
lag time
time between peak rainfall and peak discharge
centre-pivot irrigation schemes
crops are irrigated by sprinklers which rotate around a centre pivot
long profile
a graph drawn along the course of the river from source to mouth showing the change in altitude
knick point
a steep region along the river profile which disrupts the ideal concave shape
flocculation
when particles clump together (especially clay bonding along its flat edge)
thalwag
the path of least resistance where the water is flowing that fastest
mean fall/settling velocity curve
represents the average velocity at which sediment of a certain size will no longer be transported and will instead be deposited
mean critical erosion velocity curve
average velocity at which a river is able to entertain (pick up) sediment of a particular size
turbulent flow
flow over rough beds
bification
flow over rough beds
eyot
small island in a river
helicoidal flow
the cork-screw-like flow of water in a meander
wetted perimeter
the perimeter of the cross sectional area of the river that is ‘wet’
hydraulic radius
the cross sectional area / wetted perimeter – a measure of efficiency - high HR = more efficient
abrasion
the erosion of the bed and banks by the load carried
attrition
the erosion of the load being carried, producing smaller, rounded particles
hydraulic action
force of air and water on the sides of the river and in cracks
solution (erosion)
the erosion of the bed and banks by chemicals in the water
solution (transport)
minerals dissolved in the water
suspension
smallest particles carried above the riverbed by the current
saltation
small particles move along the riverbed in t a series of ‘bounces’
traction
pebbles pushed along the riverbed by the current
competence
the diameter of the largest particle that can be carried by a river
capacity
largest amount of load that a river can carry
turbulent flow
where there are higher velocities and an increase in bed roughness - associated with hydraulic action
laminar flow
smooth, straight channel with low velocity, allows water to flow in sheets parallel to the channel bed
bluff
another word for river cliff but also used to describe the edge of a river terrace
hydrological cycle
the cycle of water between atmosphere, lithosphere and biosphere
percolation
the downwards movement of water from the soil into the bedrock
throughflow
the flow of water through the soil through percolines
baseflow
the part of the river discharge provided by groundwater seeping into the riverbed
spring
natural flow of water from the earths surface, occurring when the water table occurs at the surface
