Cutting off the meanders

I ended up experimenting with making meanders today. I found that if you add just a little bit of extra "sand" to the lateral accretion areas (e.g. point bars) you end up producing very strong meanders. Particularly if you reduce the slope of the table.


Here's a shot of a few oxbow lakes being formed mid-run.


Here's a quick time-lapse video that demonstrates how adding extra material to the point bars rapidly increases the sinuosity of the stream. Keep in mind that the only thing I did here was to add sediment to areas of accretion. I didn't dig any channels or remove any material. I did have to add sediment along the floodplain in a few places to compensate for the change in gradient as the sinuosity increased.

Braided Streams of Yore

The image above is from Dunn County - along the Lower Chippewa River in western Wisconsin. The dark squiggly lines in the farm fields are the remnants of braid bars. If you look at an image of the Lower Chippewa River today, you will note a distinctly meandering pattern. Why the change? Largely due to the input of sand and gravel from the big ice sheet about 20,000 years ago. All that shifting sand helped create an unstable river bed. Couple that with highly episodic flow and you have the main ingredients for a braided stream morphology, rather than a meandering one. Now that the glaciers have gone, the sediment supply is diminished, vegetation has helped stabilize the banks, and the river is cruising around a single, meandering channel.