Preview - River Channel Forms

River Channel Forms

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River Channel Forms (20:00)

Item# 803
©1982

This program analyzes the dynamic nature of rivers and the relationship between their forms and processes. It examines the various functions a single river needs to perform, and shows how to measure river form and process, relate the two, and synthesize several attributes of the form of a river channel. It examines the differences between low and high flow, and explains how to calculate the quantity and velocity of water transport and how to attempt to measure the amount of bed-load. It compares bankfull and low flow and upstream and downstream discharge, shows how man's intervention has solved a low water problem, and asks students to try to deduce what will occur during a flood. (20 minutes)

Segments in this Video - (7)

1. River Channel Process and Form (02:14)

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Changes in the relative amounts of water and sediment rivers carry cause them to adjust their forms. River channels are shaped by the processes at work in them.

2. River Channel Shape at Low Flow (02:25)

Measurements from two survey points along a river show differences in its channel. Upstream the river channel is braided, while downstream there is a narrower and deeper single channel.

3. River Discharge at Low Flow (03:10)

Water discharge under low flow conditions is measured at two points of a river that have different channel characteristics. Results indicate that velocity and discharge increase downstream.

4. Measuring River Sediment & Bedload (03:00)

Measuring the size of the bedload at two survey points of a river indicates that bedload size decreases significantly as the river moves downstream.

5. River Width-Depth Ratio (03:14)

Water volume increases and bedload size decreases as a river moves downstream. To determine how channel shape adjusts to these changes a channel's width is compared to its depth.

6. Bankfull Conditions (03:33)

Bankfull discharge at the upper survey point of a river is much greater than low flow discharge at the same point. At a point downstream there is also a greater, but less dramatic, increase.

7. Flood Control Interventions (01:43)

A man-made river channel has been built along one stretch of a river to try to reduce flooding. A bedload trap was also built to help keep bedload from accumulating in the man-made channel.