1. Hydrology info

Phreatic zone vs Vadose zone

Phreatic = permanantely saturated - pp

Vadose = seasonally saturated and unsaturated

Define Artesian well

impermeable rock pushes on aquifers exerting high pressure causing water to rise to surface

Drainage density equation

Total length of all streams in a drainage basin divided by area of drainage basin

Names as many drainage basin characteristics as possible

Precipitation intensity/duration/type, vegetation, climate, land use, rock/soil type, PEVT, drainage density, basin size/shape, relief

Name the five types of erosion

• Hydraulic action - force of water removes rock particles from bed/banks

• Corrasion/abrasion - rock acts like sandpaper rubbing against bed

• Solution/corrosion - acidic rainwater dissolves rocks

• Cavitation - air bubbles trapped in water get compressed and then implode weakening rocks

• attrition - erodes bedload as bedload knocks into eachother/bed/banks

Explain Hjulstrom curve - axis, lines, regions, why lines change

• logarithmic scale

• River velocity on y-axis, bedload size on x-axis

• mean erosion velocity curve = minimum velocity of water flow required to engage/erode a particle of that size

• mean setting velocity curve = velocity required to maintain a particle of a given size

• small particles have strong electrostatic charges to bind to river bed, difficult for water to get under clay

Define flocculation

Many small particles sticking together to form a larger particle

Define hydraulic radius

cross sectional area divided by wetter perimeter

represents efficiency of river channel

High hydraulic radius means an efficient channel as there is less friction

Name three types of river flow

Laminar

Turbulent

Helicoidal

Explain formation of waterfall/gorge + know meander/levees

• The river crosses a discontinuity in the underlying geology (i.e. a place where two different rock types exist next to each other). Harder, more resistant rock (e.g. Igneous rock) overlies softer, less resistant rock (e.g. Limestone).

• Waterfall forms where river processes interact with the underlying geology (rocks). Erosion process - such as hydraulic action, abrasion, solution - erodes the soft rock.

• This creates an overhang. Pieces of bedload swirl around in this plunge pool due to high energy falling water. This leads to high amounts of abrasion.

• The hard overlying rock is now unsupported and collapses into the plunge pool

• As the process repeats itself, the waterfall retreats upstream.

• This creates a steep-sided gorge downstream of the waterfall.

Define point bar, spliff off slope and river bluffs

Point bar = bed of gravel on inside bend of meander due to deposition

Slip off slope = relatively flat area of land on inside bend of meander

River bluff = a relict river cliff - not as steep and not near site of active erosion

What two factors make up risk

Frequency and severity

Physical factors of flooding

Prolonged/intense rainfall, tropical storms/monsoons, snowmelt, tsunami, landslide, Jokulhlaup, drainage basin characteristics, aspect

Jokulhlaup = volcano erupts beneath a glacier causing a large increase in meltwater

Human factors of flooding

Ploughing direction, urbanisation, deforestation,

Name all hard engineering flood management strategies

Dams, river straightening, artificial levees, diversion channels

Name all soft engineering flood management strategies

Afforestation, wetland conservation, flood plain zoning

Define recurrence intervals

Predicted time period between a flood of a certain size based on previous flood data