Question 17 of 21: Question 6, Part 2: Define Terms

Question 6, Part 2: Define Terms (8 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

a) Oxbow lake. A crescent-shaped standing body of water formed when a mature, meandering river erodes through the narrow neck of a tight meander loop, cutting a new, shorter channel and abandoning the old loop, which becomes isolated from the active channel and gradually silts up and fills with vegetation.

b) Meander. A sinuous, looping bend in a river's course, produced by the combination of erosion on the outer (cut) bank (where flow velocity and shear stress are highest) and deposition on the inner (point-bar) bank of a low-gradient stream; meanders migrate and tighten over time.

c) Levee. A raised, elongate ridge of sediment running parallel to a river channel, built up (naturally, or artificially reinforced) when a river overtops its banks during floods and the coarsest suspended sediment drops out immediately adjacent to the channel as flow velocity abruptly decreases outside the confined channel.

d) Tide-dominated delta. A delta whose shape is controlled by strong tidal currents reworking river-mouth sediment into elongated, funnel-shaped sand bars and channels aligned with the direction of tidal flow, rather than into the branching distributary "bird's-foot" form of a stream-dominated delta or the smooth, wave-straightened shoreline of a wave-dominated delta.