Base Level The lowest level to which a

Base Level The lowest level to which a river can erode: base level High above base level: much erosion Closer to base level: less erosion 16. 04. b 1 Landscape reflects decreasing gradient Sea level is ultimate base level

Curves in Rivers and Streams This river is braided This river has meanders

Curves in Rivers and Streams Braided: network of interweaving channels Low sinuosity: gently curved Meandering: very curved; high sinuosity

What Processes Operate on Meanders? Small graphs show profiles across the river channel; observe the channel profiles for different parts of the river Straight channel: symmetric, fastest in center Outside bend: deeper and faster; erosion of cutbank Inside bend: shallow and slower; deposition of point bar 16. 05. b 1 Erosion and deposition may be balanced

How Do Meanders Form and Move? Faster side erodes and deepens Deep side faster and more water, so erosion Inside slower and less water, so deposition Erode outside bend, increasing curvature; migration outward and downstream Erosion or overflow erosion: cutoff meander and oxbow lake 16. 05. c 1 -6

Observe the features of a low-gradient river One channel with meanders, point bars, and cutbanks Meander scars, cutoffs, and oxbow lakes Floodplain with gentle gradient 16. 08. a 1

Observe this stretch of the Mississippi River for features typical of low-gradient rivers Meander scars Point bar Oxbow lake Cutbank Cutoff meander Meander 16. 08. b 2

Landforms in the Headwaters of Streams Waterfall Rapid: turbulent segment 16. 06. a 3 Mountain lake

Landforms of Mountain Streams and Rivers Incise into bedrock; narrow canyon if incision faster than widening Braided channels in less steep areas Dump debris when reaching more gentle terrain 16. 06. b 1

Observe this view of a braided river River has steep gradient onto plain Glaciated mountains: abundant sediment supply Sedimentrich river braided to ocean 16. 07. a 1

Close-Up Views of Braided River Braided channels: steep gradients, abundant supply of sediment, and variable flows Part of fairly straight river 16. 07. a