Review of Lecture Notes on Drainage Basins

Flashcards to review lecture notes on drainage basins and related concepts.

What are the three components of natural systems?

Outputs, Stores, and Flows

What is a drainage basin?

The area drained by a river and its tributaries.

What is the boundary of a drainage basin called?

The watershed

Define 'Evaporation' in the context of a drainage basin system.

The change in state of water from liquid to gas, caused by solar energy, leading water to leave the system.

What is Evapotranspiration?

The combined processes of evaporation and transpiration, where water turns into gas and rises into the atmosphere

What is River discharge?

The volume of water passing through a cross-sectional point of the river at any one point in time, measured in Cubic Metres Per Second (Cumecs).

What is Interception?

Water (e.g. precipitation) that is intercepted by plants’ branches and leaves before reaching the ground and stored short-term.

What is Soil Water?

Water that is stored in the upper levels of the soil, which is utilised by plants.

What is Surface Water?

Water stored in puddles, ponds, lakes etc. Dependent on the size of these stores, they can last from hours to millions of years.

What is Groundwater?

Water that is stored in the pore spaces of rock or lower soil.

What is Channel Storage?

Water that is stored in a river’s channel.

Define Throughfall.

Water flows from leaves and foliage onto the ground. prominent in areas with a large canopy that receives a lot of rainfall, like a rainforest.

What is Stemflow?

Intercepted water stored on plants and trees flows down a stem onto the ground.

What is Overland flow?

Water flows above the ground, as sheetflow (lots of water flowing over a large area), or in rills (small channels similar to streams, that are unlikely to carry water during periods where there is no rainfall). Overland flow will occur when water cannot infiltrate the soil.

What is Channel flow?

Water that moves through established channels , like streams or rivers.

What is Infiltration?

The movement of water from above ground into the soil.

What is Percolation?

Water flows from the ground or soil into porous rock or rock fractures.

Define Throughflow

Water flows through the soil and into streams or rivers.

Define Groundwater Flow

Water flows through permeable rocks, below the water table, and may also flow as springs.

What is Baseflow?

The level of channel flow when there is no overland flow (when no precipitation has fallen).

What is the water table?

The level at which the pore spaces and fractures in the ground become saturated.

Define Groundwater recharge.

Replenishing of groundwater levels. Groundwater levels fall when groundwater is being used more.

What is a spring?

A natural outlet of groundwater, i.e. it is any place where groundwater flows out onto the surface.

What is a hydrograph?

A graph that shows how river discharge changes over time.

What does 'Discharge' mean in the context of hydrographs?

The volume of water passing through a cross-sectional point of the river at any one point in time, measured in Cubic Metres Per Second (Cumecs).

Rising Limb

The line on the graph that represents the discharge increasing.

Falling Limb

The line on the graph that represents the discharge decreasing.

Lag Time

The time between peak rainfall and peak discharge.

Baseflow

The level of water that the river holds without contributions by overland flow.

Stormflow

This is the additional water in the river bank during a storm, comprised of overland flow and throughflow.

Bankfull Discharge

The maximum capacity of the river. If discharge exceeds this then the river will burst its banks and be in flood.

Flashy Hydrograph

Short lag time and high peak discharge, most likely to occur during a storm event, with favourable drainage basin characteristics

Subdued Hydrograph

Long lag time and low peak discharge.

Antecedent moisture

Pre-existing level of moisture within soil before precipitation. The level of moisture in the soil affects the amount of infiltration , which therefore affects hydrographs.

What is drainage density?

The total length of all rivers and streams in a drainage basin divided by the total area of the drainage basin.

Name the four types of load transportation of a River.

Traction, Saltation, Suspension, and Solution

What is Deposition?

Where the river drops its load when the river no longer has enough energy to carry the load.

What is the Hjulström Curve?

A graph that shows how the velocity of a river affects the river’s material.

What is Thalweg?

This is the line of fastest flow (maximum velocity) within a river. This is also the deepest point within the river channel

What is a gorge?

A steep sided, narrow valley with a river flowing through it, is formed when a waterfall continually retreats over time.

River cliff

A cliff created when the bank is undercut by erosion on the outside of the bend.

Point bar

A deposit of fine sediment, such as sand, on the river bank inside of a meander bend.

What is a bluff?

A large, rounded cliff on the side of a river, are formed on the outside bend of a meander, where erosion is dominant.

Riffle

The higher , shallower area of the sequence, characterised by deposits of material

Pool

The lower, deeper area of the sequence

What is a floodplain?

A large, flat area of land near a river, that forms due to erosion and deposition.

What are Levees?

Natural embankments along a river that build up due to repeated flooding.

Where do deltas form?

At the mouth (end) of a river, where the river carries a large amount of sediment.

What is deforestation?

The removal of trees by felling, burning, or other means of removal.

Afforestation

The planting of trees in an area without trees.

What is 'Abstraction'?

The removal of water from a water body, such as a river, lake, reservoir, or groundwater store.

What is Flood forecasting?

Uses precipitation forecasts to estimate the level of flooding risk in an area.

What is channel straightening?

Where bends and irregularities in the river channel are removed using machinery, leaving a straight channel, e.g. by cutting off meanders.

What is a diversion spillway?

A constructed channel that allows excess water to flow into it when the channel is overflowing.

Name two examples of sustainably managing the area around the river channel can limit flooding risk.

Afforestation and tree management, and Floodplain land use management

Examples of Wetland conservation.

Banning or limiting the drainage of wetlands and Monitoring changes

What is River restoration?

Refers to the process of restoring a river back to its original state before it was altered.