7. Effects of changing estuarine geometry (15 pts): Most estuaries have been mad

Question

7. Effects of changing estuarine geometry (15 pts): Most estuaries have been made narrower, deeper and straighter, with a more regular bed, so that larger ships can enter, and to provide shoreline space for industry, ports, agriculture, etc. We will discuss the dynamics effects of these changes during the course, but it is worthwhile thinking about this qualitatively. How do you think changing the entrance depth of the Columbia River estuary from about 6m deep and 10km to 18m deep and 5 km, with a narrow and quite regular channel has affected the following a) b) c) Bed friction: higher or lower Salinity intrusion: more or less salt in the system Tidal range your reasoning Explain

Explanation / Answer

A)low

B)less

C)high

Explanation given below

River channel being deeper and wider applies that there is less intraction with the rock bed beneth

Hence less friction.Thus the bed friction gets reduced.

Hence less intraction with the bed surfuce the mixing becomes less effective and the flow will be efficient . A laminar flow will be occurring in this case.

But as the widening of the channel surface reduces there will be more hindrance produced by the sides of the channel hence tides will be higher.

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