How to Build a River



…or, at least, features of a natural river that could be duplicated manually.


The photo above is of Hinkson Creek in Columbia, Missouri, looking upstream.  This particular stretch is a bedrock stream, lined on both banks with deciduous forest and containing deposits of gravel and large stones across the bottom, as point bars, and along the banks.  A large bedrock cliff face lines the right bank (left side of the photo) and ties into the bottom of the channel.  (Left and right bank designation is indicated when looking downstream.  All photos are taken from a stony deposit on the left bank.)



Just downstream of the first photo, the stream becomes significantly shallower, and is approximately 10-12 feet wide.  Presumably natural stone and gravel deposits line both banks, ranging in size from less than an inch to about the size of a fist.  At this particular location, a line of larger stones spans the stream, trapping leaves, small rocks and other debris, allowing water to trickle over them with a pleasant sound.  This shallow area is known as a riffle.  (Note: goofy sister not included in manmade river.)



Another picture of the riffle with upstream depth scale.  Depth is about mid-shin.



Another slightly different view of the riffle and some of the vegetation along the bank, which is some kind of finer-grained material.  Also is some of the point stone and gravel point bar along the right bank.



Downstream of the riffle and showing just how extensive the point bar along the right bank is.  Note the direction of the stream meander: the vegetated left bank shows signs of erosion of the fine-grained material, while the right bank shows the deposit of gravel.  Streams erode along the outside of a bend, and deposit on the inside of a bend.



Another close-up shot of the riffle.  Angular stones of varying sizes are preferable over round stones of the same size.  Rocks in a stream will eventually become rounded, but angular stones of several sizes will allow for better interlock, and larger stones will keep smaller ones from being washed away by larger water flows.



Slightly different angle of the riffle.  Note the turbulence in the water as it trickles over the rocks.



A calmer section of the stream.  Compare the status of the water with that of the previous photo.  The volume of water coming in is more or less equal to the volume of water going out, so the water in shallow areas has a higher velocity in order to transmit the same volume of water as deeper areas.



An overall shot of the stream including the area upstream of the riffle.  This particular location had very little in the way of sticks and branches in the stream itself, but deposits of large woody debris along the edges of the point bars and in shallower portions of th stream would not be uncommon.



Just downstream of the riffle forms a pool.  This area is somewhat deeper, closer to knee depth, so the water is calmer and slower-moving.  Most of the gravel was deposited within the riffle, so the bedrock bottom is easier to see within the pool.



This particular photo is taken standing on a bedrock ledge.  Some large, woody debris lines the left bank, predominantly large branches and leaves.  They were likely deposited during a time of high water.  Erosion of the roots above the top of the debris deposit may have been caused by the creek, but is more likely due to runoff down the steep slope.