Levees From The Meandering Stream EarthCache
Levees From The Meandering Stream
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The Assiniboine River has carved much of the geography of south central Manitoba. From the sand dunes at the Spirit Sands in Spruce Woods Provincial Park (and other sand deposits from Brandon to Portage, and all points south) to the delta at the south end of Lake Manitoba formed during a time when the Assiniboine ran northward. One of the characteristic landforms left by this slow moving flatland river are many natural levees.
Levees are formed during flood periods of the river, when the rising water carrying sediment floods its banks. The heaviest particles drop out of the flooding water the earliest as it leaves the rapid flow, creating sand and gravel bars. Dirt and clay are carried further from the river bank out onto the floodplain. The action of the coarser particles dropping out of flow causes the riverbank to rise, and creates the levees to mark the flood. As the river continues to erode its outer banks at its curves, the inner banks are built up by the deposition of sediment due to the slower flowing water. Thus, in areas of meanders the land is lined with ridges that are the remnants of these levees.
One of the secondary effects of this action is that the river itself slowly rises above its floodplain. This occurs because during non-overflooding years, and during times of low flow, sediments drop out onto the river bottom, and raise the river level in its steep walled channel. The waters of any flood which then occurs will move across the floodplain, and not return to its own riverbed. This is the situation northwest of here near Baie St. Paul, where the Assiniboine is higher than the prairie south of it, and where the concern in 1997 was that the rising waters would flood across country to the La Salle River. Provincial Road 424 is in effect a dike to contain any flooding of the Assiniboine from moving south across the plain. See our cache GC1BQ89, “A Dam Or A Road?” (A similar situation occurred near Sanford and Brunkild, where the flooding Red could have dumped into the La Salle, and thus made it around Winnipeg’s Floodway and into the city, hence the Z-dike was built.)
1. The first task in this earthcache is to walk around the bend in the Wild Grape Trail in Beaudry Park from Point A to Point B and count the number of natural levees one crosses performing this task. Please stay on the trail so as not to carve new trails. Email that number to the cache owner. Please don’t post it in your log. (If you want to see even larger levees, cut north south across the maple trail where the ‘peninsula’ it is at its widest and you’ll see even more impressive ridges.)
2. Take a picture of your GPS and/or you and your group along the walk, with one of the larger levees in the background. Be sure your GPS is in the picture. Post this picture with your log.
Please remember to keep the park clean and pack out any garbage you bring in. Please also practice CITO and remove any other garbage that careless park users have left behind. Thank you from bergmannfamily, and Parks Manitoba. Happy caching!
Additional Hints
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