Ecology Meanders In Nature Hamilton
Wednesday 20 April 2011
“Oh the river that meanders suggests a valley with low slope: As it twists and turns and cuts a course…an aquatic king of grope; For the river, twisty, twisty river, looks a bit like some blue rope.”
Kenton M. Steward
River and Stream Bends Work
The meander is one of several interesting shapes that form exquisite patterns found repeatedly in nature ! Meander is a bend in a sinuous (channel type) watercourse. All streams (rivers, creeks) are sinuous at some time in their geological history over some part of their length. Over time, rivers of water form into a shape called a meander as they wear away at the soil along the edges which are viewable from the ground level or from an airplane window. A river can have concave or convex banks. A meander is meander geometry or planform geometry with irregular waveforms or a sincuous waves (one thick line on the stream or river). The direction of the river usually meanders down a low valley on its axis. The curvature of the meandering stream varies from the apex (maximum point) to zero at a crossing point (straight line) which can be called inflection basically due to the curvature changing direction in that vicinity. In ancient Greek, the term was Maiandros or Maeander was meant for the Meander River which is east of ancient Greece in the town of Miletus which is today Milet, Turkey. Rivers rarely maintain a straight route as they travel to large rivers, lakes or oceans. Therefore, they take a series of bends and smooth loops that snake across the landscape.
This snaking pattern goes back and forth across a low valley (like Dundas Valley) because a stream, creek or river that may assume a meandering course, alternatively eroding sediments from the outside (shoreline) of a bend and deposit them on the inside. The meander is formed when moving water in a river, creek or stream erodes the outer banks and widens in the low valley. It is the bending of the river that is known as a meander. These bends reflect the way in which a river minimizes resistance to flow, therefore, spreading as evenly as possible along the river course the energy of the water. This is how it works: if you try to swim a meandering river one observation would be the velocity of the moving water was not the same everywhere you swam. That is because the velocity is at the lowest point along the bed and walls of the river ultimately due to the water as it encounters the most friction and therefore the flow of the water is reduced. In a straight channel segment of the river. creek or stream the water moves faster in mid-channel especially near the surface. But , as the water moves around the bend (meanders) the high velocity of the water swings to the outside of the channel. It is when water rushes past the outer part of the bend (meander), the sediment is continuously eroded from the riverbed and is swept downstream. On the innerside of each bend it is a slower flow of water and coarse sediment that accumulates and forms distinctive point bars. This creates a meandering pattern along the course of the river with shallow water and point bars on the inside bends and steep banks on the outside. The material lining of the banks is not uniform along the river system therefore another landform – an oxbow lake, can develop. It is the resistant sediment that slows downstream and other meanders on the same river that mitigate through softer sediment upstream as they intersect the slower-moving meander and cut off the channel between the two forming an independent loop that will become a lake (oxbow). Lake Ontario has many example of meanders. For example, Hamilton Harbour, a harbour or river bar is a sediment deposit formed at the harbour entrance or river mouth by the deposition of sediment or the action of waves on the sea floor.
In Lake Ontario, the separation is the barrier beach (Burlington Bay in the east of Hamilton). The meanders are from a drowned river in glacier times of the lake. But, in the west end of Hamilton the river mouth spreads into a River Mouth Marsh (Cootes Paradise). This is fed by the Spencer Creek Watershed that include the following Creeks : Fletch, Flamborough, Logie’s, Westover, West Spencer, Ancaster, Borer’s Chedoke, Spring, Tiffny, Sulphur, Sydenham and Westdale. M.R. Pozze, J.J. Bryers and W.A. Morris from McMaster University School of Geography and Geology published a paper entitled “Lake-based magnets mapping of contaminated sediment distributing it on Hamilton Harbour, Lake Ontario, Canada.” These researchers investigated three concepts, namely: (1) Contaminated Sediment, (2) Environmental magnetism, and (3) Magnetic susceptibility. Other Lake Ontario meanders include: Hyland Creek River near Scarborough that flows into Lake Ontario; the Humber River that flows south into Lake Ontario; and, Keating Channel that empties into Toronto Harbourfront and Lake Ontario. Hamilton’s Cycling Paths are also noted for their meandering paths.
Greek and Roman art, especially Greek vases from the Geometric Period have ocean-like patterns of waves. In art and architecture repeated motifs are shaped from a continuous line into a decorative boarder called meanderings. In protecting our Canadian environment an ocean going yacht and coastal cruiser called Meander is a historical ship. That is, because in 1977 the ship Meander acted as Greenpeace IX stopping supertankers from coming into British Columbia waters at Vancouver. In Greenpeace IX, the ship Meander was a blockade to nuclear submarines attempting to enter Hood Canal. It also served in FY11 in WW11. In the 1950s and 1960s it was a coastal cruiser on the west coast of Vancouver Island. In 2,005 at the Victoria Classic Boat Show it won “Best Boat Of The Show” award. The original owner George Kidd, wanted a ship that would go anywhere in the world.
Sources: Canadian Geographic Magazine; McMaster University School of Geography and Geology; Royal Vancouver Yacht Club;
Doug Worrall Photographer