Drainage Basin Hydrology and Geomorpholgy

Possible essays: river processes of erosion, transportation and deposition and spatial and temporal factors influencing their operation, including channel characteristics and seasonality

Hjulstrom Curve

Hjulstrom Curve

Model showing how velocity affects the erosion, transportation, and deposition of different load particle sizes. Critical erosion velocity curve and settling velocity curve

Stream Order

Strahler

Bifurcation Ratio

Indicates shape of basin and runoff behaviour

High bifurcation ratio indicates short time of concentration, high flooding probability

Average of ratio of number of streams in an order to number of streams in the next highest order

Water Budget

97.2% Salt Water, 2.8% Fresh Water

2.15% Frozen, 0.62% Ground, 0.03% Lakes, soils, atmosphere, 0.0001% Rivers

Distance Source to Mouth

Actual distance/straight distance = pi

Pool to pool/riffle to riffle

6x bedwidth

Sinuosity

Thalweg length A to B / straight line A to B

Delta Types

Nile: Wave-dominated

Mississippi: River-dominated

Ganges: Tide-dominated

River Regime

Average levels over time(typically by month)

Hydrograph

Shows a storm over time with discharge and rainfall

Peak rainfall + discharge, rising limb, falling limb, base flow, storm flow, and lag time all shown

Affected by rainfall type, drainage density, saturation, geology, etc.

Drainage Basin Density

Ratio of total length of streams within a drainage basin to the total area of the drainage basin, higher value indicates higher stream density and faster storm response

Discharge

Volume of water passing a point in one second, cross-sectional area(m²) x velocity(m/sec), cumecs

Hydraulic radius

cross-sectional area/wetted perimeter

Gauging Station

Measure discharge, predicts floods

Schumm Model

Models rivers(discharge, channel width, depth, velocity, gradient) over three zones(upland, flood plain, estuarine)

Factors Affecting River Velocity

• Gradient

• Flow Type → turbulent in UC vs laminar in LC

• Channel Shape

• Roughness → Manning’s coefficient calculated from velocity, hydraulic radius, slope

Dew Point

Pressure and temperature at which water vapour condenses