Question 1 Report
Fig. 1 shows a longitudinal section of a wadi in a hot desert after a high-energy flash flood. The field team found coarse boulders in the upper section and a broad deposit of finer sediment lower down. They also noted that floodwater had cut a small channel into the valley floor. Use the shown figure to describe changing river processes.
(a) Which section is likely to have the greatest river energy during a flood: upper, middle or lower? [1]
(b) Outline how a flash flood can transport a large boulder. [2]
(c) Draw and label two landforms that could develop where the wadi leaves the valley. [2]
(d) Outline one reason why building homes on this lower section may be hazardous. [2]
(a) Upper section [1] (b) Fast, deep floodwater has high energy [1]; it can roll/drag boulders by traction [1]. (c) Any two correctly drawn and labelled: alluvial fan [1]; braided channels/distributaries [1]; sediment deposit [1]. Maximum [2] (d) Flash floods can arrive rapidly [1]; water and sediment may inundate/bury/damage homes [1]
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