Geomorphology Flashcards
What is a catchment area?
The drainage area that supplies water to a river
The water comes from rainwater, which flows down the slope and from underground water which seeps into the river
Drainage basin
Area drained by a river system
Watershed
High ground separating one drainage basin from the adjacent drainage basin
Confluence
Point where one river in the network joins another
Interfluves
Ridges of high ground between individual channels
Types of rivers and their description (4)
- Permanent: receive groundwater all year
- periodic: groundwater only in the rainy season (flow for 5-6 months after rain)
- Episodic: no underground water (flow for a few hours after rain)
- Exotic: flow all year (more water at source, less as you move away)
What factors affect drainage density?
- high evaporation rates = lower DD
- high rainfall regions = high DD
- large amount of infiltration = lower DD
- hardness of rock - channels in soft rock = higher DD
What is stream order?
The category of a stream in an network determined by the order of the streams feeding into it.
What is discharge of a river?
The amount of water flowing in a river channel past a point at a given time
Laminar flow
Water flowing in sheets; it does not change levels
Turbulent flow
Water flowing in a bubbling motion; it changes levels
Headward erosion
A river lengthens its course by cutting back upstream above its original course
Graded river
A river that has achieved equilibrium between its gradient, volume and channel shape, so that the river has sufficient energy to flow, with erosion rates in balance with the deposition rates
Overgraded river
River that has excess energy and therefore erode their channels
Undergraded river
Rivers that do not have enough energy to flow and to transport their load; they will deposit some of their load
What is a rejuvenated river?
A river receives additional energy and begins to erode vertically
Fluvial landforms resulting from rejuvenation
- valley within a valley
- river terraces
- knickpoint waterfalls
- entrenched and ingrown meanders
Superimposed drainage pattern
A river develops a pattern on a surface that has eroded over time, so now the river is flowing on the older rocks or structures that have been uncovered
Antecedent drainage pattern
After the river formed, folding or faulting occurred, but the river maintained its pattern, cutting a gorge through the land that has been uplifted
The importance of water sources
- fresh, clean water supply is essential for human health
- rely on water for many activities (agriculture, industry, hydroelectricity)
- birds and wildlife depend on rivers and vegetation in the riparian zone
The importance of wetlands
- remove harmful bacteria
- reduce the acidity of water
- wetlands act as a sponge - reduces flood damage and ensures a steady supply of water all year
Why drainage basins and catchment areas need to be managed
- everyone can have access to water
- river ecosystems remain healthy
- flooding can be controlled
Impact of people on drainage basins and catchment areas
- human activities pollute groundwater
- over-grazing decrease infiltration of water
- runoff is polluted and harms the aquatic life
- impermeable surfaces (concrete and tar) creates a decrease in infiltration and water flowing over land increases
Catchment and drainage basin management
- avoid construction on the flood plain
- educate farmers on environmentally sustainable farming practices
- maintain vegetation in the riparian zone
- conserve and restore wetlands
- make public aware of the need to conserve water
