Many of the people I meet tend to visualize streams and rivers as unchanging features of the landscape (wrong). I have met plenty of property owners in urban settings that are unhappy with the creek that changed course and is now eating into their yard…it even knocked part of their fence down. Somehow, these property owners have a small dog that can now escape and they are very worried. I promise you, there is always a small dog.
Channelizing a stream
In the drainage industry, you get to see lots of water. And ditches, streams, and hollers, etc. It has been interesting to watch how water shapes its own path and charts a meandering course. Let us take a tour and see how people make alterations that make some interesting and unintended changes to the landscape. In this post, we will examine small waterways and ditches in an urban setting.
In the above picture, you can barely see the black drainage pipe in the bottom left; I am standing on the road. For eight years, I completed construction, monitored, and made adjustments to this ditch so it would properly flow water.
Why the adjustments? Because you could watch the water slowly start to create a winding path at the bottom of the ditch. This was fine in some locations, but not in other areas with critical utilities. If left unattended, this drainage ditch would become overgrown with trees and the water would cut its own path to the drainage pipe under the road. This is how I found it before I had it reconstructed. We also found part of a car, refrigerator, and lots of trash. It was pretty messed up and water did not flow.
This small stream was originally channelized in the 1990’s when the subdivision was constructed. Basically, it was straightened so the homes could be built. As you can see in the above photo, the bottom and top of the stream have a slight shift to them, while the middle appears to be fairly straight. However, if you walk this stream segment, you can easily see that the stream is working towards creating several curves that will eventually eliminate the straight areas. The easy floodplain access helps slow the water down and is keeping the stream channel from quickly changing.
In this picture, you can see that the stream has nowhere to easily flood; this means lots of fast-moving water. This site was channelized about 30 years ago; you can see that the width of the stream is about one excavator bucket wide. This stream segment was straightened for about 600 feet. Prior to reconstruction, this area had numerous problems, primarily caused by the water velocity. The banks were terribly eroded and multiple utilities and yards were being destroyed (see the picture below). It took a significant amount of money to repair this stream segment. You can see the homes on the right.
This image is directly upstream of the one above it. You can easily see the utility lines hanging in the air; at one time they were buried. A utility pole and multiple utility boxes were directly behind me, also in danger of being damaged. Again, note the high banks and heavy erosion (in this picture, water is flowing towards me). At the top, left side, water is banking hard off the nearly 90 degree bend and hammering directly into the opposite side of the bank, causing a significant amount of damage. There is no floodplain access to dissipate the energy of the fast-moving water.
The flood finale
While is would be easier to visit these sites in person to see what I am describing, I hope that I got the message across. Limited floodplain access means higher water velocity, which in turn leads to heavy erosion and damage to the stream corridor. In the above pictures, the streams were “channelized” and the ditch was created solely to move water as quickly as possible away from the subdivision. While these are not necessarily bad things, they can cause unintended consequences at the site and immediately downstream. In the next post, we will take a look at some additional stream segments and see how they are holding up in the urban environment.