Geography 4.6 Flashcards
What is meant by the long profile of a river?
The long profile shows how a river’s gradient changes as it flows from its source to its mouth. You can draw a diagram of a river’s long profile either by drawing a quick sketch based on some previous knowledge or by plotting the height of the river above sea level at various points in its course. Its a side on diagram of the rivers height and gradient whereas a cross profile shows the river head on sliced in half.
How dose the river Eden’s landscape change along its long profile (upper/middle/lower). Consider: channel shape, valley profile, gradient, discharge, velocity and sediment size and shape?
When a river is near its source, it often develops a V-shaped valley as the river erodes down (this is called vertical erosion). At the same time, weathering breaks up material on the valley slopes. Weathered material from the valley sides gets deposited in the river. This material is carried by the river and erodes the riverbed through abrasion.
What are the reasons for these changes?
Weathered material from the valley sides gets deposited in the river. This material is carried by the river and erodes the riverbed through abrasion.
Compare hydraulic action with abrasion
Attrition is the erosion of the river bed. The abrasion of a river is when the rocks, sand and pebbles erode the river bed. Hydraulic action occurs when the motion of water against a rock surface produces mechanical weathering
Define weathering
Rocks gradually wear away. This is called weathering. There are three types of weathering:
physical weathering
chemical weathering
biological weathering
Compare freeze thaw and biological weathering
Water expands slightly when it freezes into ice. This is why water pipes sometimes burst in the winter. You might have seen a demonstration of this sort of thing at school - a jar filled to the brim with water eventually shatters after it is put into a freezer.
Animals and plants can wear away rocks. This is called biological weathering. For example, burrowing animals such as rabbits can burrow into a crack in a rock, making it bigger and splitting the rock.
Compare traction with suspension transport
Traction - large boulders and rocks are rolled along the river bed.
Suspension - fine light material is carried along in the water.
Explain the stages and processes responsible for waterfall formation, v shaped valleys and interlocking spurs, meanders, ox-bow lakes, flood plains, levees and deltas. Do each of these in turn - this is a big question!!
As the river moves through the upper course it cuts downwards. The gradient here is steep and the river channel is narrow. Vertical erosion in this highland part of the river helps to create steep-sided V-shaped valleys, interlocking spurs, rapids, waterfalls and gorges.
As the river erodes the landscape in the upper course, it winds and bends to avoid areas of hard rock. This creates interlocking spurs, which look a bit like the interlocking parts of a zip.
When a river runs over alternating layers of hard and soft rock, rapids and waterfalls may form.
Explain two ways climate, geology and slope processes change the river landscape
In a warming world, the general trend is going to be toward greater water scarcity and drier rivers [19]. A major study of 900 rivers published in the American Meteorological Society’s (AMS) Journal of Climate in 2009 concluded that flows into the oceans have decreased significantly over the last 50 years, with that trend predicted to continue [5]. According to the IPCC’s 2007 report, direct climate change impacts on rivers will occur through rising temperatures and carbon dioxide concentrations, while indirect effects will be caused by changing precipitation (rainfall, snow, fog, and so on) and melting glaciers/ice. Globally, the IPCC suggests that climate change impacts on rivers will include changes in water quality, impacts on wetland plants and animals, and biodiversity loss, concluding “Changes in climate and land use will place additional pressures on already-stressed riparian ecosystems along many rivers in the world” [6].
Label the key features (lag time, rising limb and peak discharge) of a flood hydrograph
On GoodNotes
Compare a flashy and subdued hydrograph
Drainage basins come in a wide assortment of shapes. (Roughly) Circular shapes are common as are more elongated and narrow shapes. For a circular drainage basin, the river’s hydrograph can often be described as “flashy” because it will have a fairly steep rising limb and a high peak discharge.
Explain how physical factors (geology, soil, slope, basin type, antecedent conditions) can affect flood hydrographs.
heavy rainfall
long periods of rain
snowmelt
steep slopes
impermeable rock (doesn’t allow water through)
very wet, saturated soils
compacted or dry soil
