Park at the Parking Coords about 50 yards south-west of the bridge and then walk to the cache coords site which is about the center of the bridge/river channel.
Rivers are dynamic features that periodically change their courses by abandoning old channels and creating new ones. Where you are standing, at GZ of this EarthCache, is an old abandoned channel of the Black Warrior River. Today, the channel of the Black Warrior is about a mile and a half to the south.
The path a river takes from its headwaters to the ocean is affected by a huge number of factors. They range from precipitation rates, bedrock geology, topography, vegetation, tectonic movement, just to name a few. Over time these factors will change and the flow of the river changes with them. Sometimes the entire course of the river will change. The frequency and magnitude of these changes are of interest to planners and builders because they need to know the likelihood of a nearby river changing its course again, threatening cities and the type of soils they will be building on.
Tuscaloosa is the fall line of the Black Warrior River. That is, above Tuscaloosa, the Black Warrior River flows through steep sided hills with exposed bedrock on the channel flanks that limit the lateral movement of the river channel. Below Tuscaloosa, the Black Warrior River flows through a flat broad plain with limited exposed rock formations allowing the river to meander or change its channel laterally. Generally speaking, rivers erode their banks on the outside of a river bend and deposit sediment on the inside of the curve of the river bend. Over time, this eroding of the outside of the river bends and depositing of material on the inside of the curves causes a river to meander or constantly change its channel course. Periodically, whole sections of the river channel are cut off and abandoned. This is what happened to create is swamp looking area here that was once the main channel of the Black Warrior River long ago.
A river channel is the depression through which the water of a river flows during non-flood conditions. When the flow of a river changes to a new channel the old channel is considered relict. Over time these abandoned channels are filled in by flooding and dead plant material. Even long after the old channels have been abandoned, they can be identified by the soils that formed in them, the change in vegetation that grows in them, and the different infiltration rates through them. Thus, one of the easiest ways to identify old abandoned channels is on aerial photographs. On aerial photos, the vegetation and water content of the old channels stand out. Below is the aerial photo of the area.
To claim credit for a “Find” of this EarthCache send me an email with the answers for the following questions. At the top of the email please write the title: Old Channel of the Black Warrior River.
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How wide is the abandoned channel here at this bridge?Use your GPS to determine the width or use the pace method.
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What type of trees are growing in the old channel?
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Is there a flowing current in the water here?Drop a small object that will float and watch to see if object moves due to a current (do not be fooled by wind blowing over the water). Using a rope or string and a small attached weight, lower the weight to the channel bottom and determine the depth of the water here.
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