Streams and Fluvial Landforms Lecture Notes

Stream processes and Fluvial Landforms Wednesday, Oct. 9 Streams - are any moving water - no matter what the name: River, creek, run, stream, brook, branch, etc. Fluvial - Stream related processes and landforms Includes erosion, transportation and deposition.  Stream...

Stream processes and Fluvial Landforms Wednesday, Oct. 9 Streams - are any moving water - no matter what the name: River, creek, run, stream, brook, branch, etc. Fluvial - Stream related processes and landforms Includes erosion, transportation and deposition.  Stream Transportation Suspended Load Suspended Load Bed Load Stream Transportation Bed load http://www.youtube.com/watch?v=DyTKYaKbw1U  Stream Deposition When a stream’s speed slows, This is done by reducing its Capacity or Competence The Deposited material is called FLOODS Why Do Floods Occur? More water falls than the ground can soak up, so it runs off. Too much runoff causes the stream to overflow its banks, causing a flood.  Floods accumulate all overland flow in a drainage basin. The bigger the basin, the more the runoff. The more rain, the more the Fluvial landforms While discussing these landforms, remember to ask: “Why are they there?” “What processes made them?” “What is the time scale of this process?” The faster the stream velocity, the more capacity and/or competence it has When a stream speeds up, it increases its load carrying power It increases its erosive power It increases its capacity and/or competence When a stream slows down, it decreases its load carrying power It decreases it erosive power It decreases its capacity and/or competence – it will drop part of its load Floodplain Floodplain Flat low-lying area next to a stream which will flood Thalweg (not in textbook) Where the fastest water flow in the stream is located. It determines where the pools, mid-channel bars, and riffles/nickpoints are.  Alluvial Fans Commonly seen in valleys Caused by intermittent/ephemeral streams flowing into a valley. Meandering stream Stream channel that develops a sinuous form across the landscape (floodplain). Meandering stream Cutbank Outer portion of a meandering stream where erosion takes place. Point Bar Inner portion of a meandering stream where deposition takes place Cut Bank Point Bar Oxbow lake A meander which becomes separated from the stream http://media.pearsoncmg.com/bc/bc_0media_geo/interactiveanimations/noqzs/083_StreamOxbowFld_SP_GL_Ins. html Terraces develop when the base level of a floodplain is lowered, and the river begins downcutting through the old floodplain material.  Mid-channel (mid-stream) bar elevated region of deposited sediment (such as sand or gravel) with flowing water on all sides. Nickpoint – (not in textbook) An abrupt steepening of the gradient of a stream, causing riffles, rapids, or waterfalls. Niagara Falls - Braided Streams – multiple interwoven channels These form in streams choked with sediment – Platte River in CO and NE; Wisconsin River Natural Levee Sediment deposited next to a stream during a flood Delta Depositional plain at the mouth of a stream, often triangular or fan shaped. Next time: Stream Geomorphology