Flow of fastest water, Thalweg, swings from bank to bank, and when it hits the outer bend, erosion occur due to hydraulic action, resulting in the undercutting of the river bank, forming a steep sided river cliff, a concave bank. This can be observed in the cross section diagram below.
Next, due to the helicoidal flow of water in the meander, sediments are brought to the inner bend, and water being slow flowing at the inner bend deposits the sediments, forming a slip off slope, a convex bank.
Overtime, the convex and concave bank would be more obvious, thus showing the bends in a river course - a.k.a MEANDERS!
An example is the stretch of River Conwy in the North Wales, which use to be a river in the past, but now having complex pattern of meandering.
Overtime, meanders actually leads to the formation of an Ox Bow lake too. As we have learnt that erosion takes place on the outer bend, it causes the neck of the meander to become narrower, and eventually joining together. Water will then takes the shortest route, which is the straight river course without passing through the meander bend. after some time, deposition will then seal off the old meander bend, forming a straight river channel. The old meander bend that is left isolated will be called an ox bow lake!
Sean Quek
JH406.21
yup, i think deposition and erosion are two very important processes in the formation of meanders.
ReplyDeletejia min
hey!in addition, i think the concave side of the meander can be called the pool, deep side of the river, whilst the convex side can be called the riffle, the shallow side of the river(:
ReplyDeletealso, to show the helicoidal flow in picture(:
http://4.bp.blogspot.com/_HTS0iL2pEqg/SX9DGgXAThI/AAAAAAAAAC0/5yod3DhDdew/s320/helicoidal+flow+3.jpg
this is a website(: sorry.i don't know how to upload a picture into this box.XD
jiayi(:
It is interesting to see how weathering processes such as erosion and deposition have such an impact on river formations and how oxbow lakes are being formed. It shows us the link that like meanders can form oxbow lakes, slip-off slopes e.t.c. and how one thing leads to another in our system.
ReplyDeleteSubha(:
It really interesting and amazing to see how the helicoidal flow of the water, could actually play a big part in the formation of meanders, by erosion and deposition on specific sides. With the river energy involved, it further support the helicoidal flow of the erosion and deposition of particles on specific sides of the river, forming the meanders. And I think its not that the water will take a shorter route, but rather the water will take the route which requires much lesser energy, hence, oxbow lake occurs.
ReplyDeleteLuke