1 / 13

Module 1 : The Fluvial Environment

Module 1 : The Fluvial Environment. Fluvial: Relating to or occurring in a river. Possible source?. Jobs carried out by a river. CORRASION Load rubs bed and banks – abrasion – like sandpaper Most effective in flood Vertical and horizontal erosion

khoi
Télécharger la présentation

Module 1 : The Fluvial Environment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Module 1 : The Fluvial Environment Fluvial: Relating to or occurring in a river

  2. Possible source?

  3. Jobs carried out by a river

  4. CORRASION Load rubs bed and banks – abrasion – like sandpaper Most effective in flood Vertical and horizontal erosion Pebbles caught in hollows swirl to form potholes ATTRITION Bedload collides and is broken in to smaller pieces Rocks become increasingly rounded downstream EROSION

  5. HYDRAULIC ACTION Sheer force on outside of bend – water pushed into cracks – air compressed- pressure causes collapse Captivation –bubbles of air collapse -shock waves weaken banks Slowest and least effective form of erosion SOLUTION OR CORROSION Happens continuously The concentration of carbonic acid and humic acid in the water enables it to dissolve material from bed, bank and load. Humic acid derived from humus EROSION 2

  6. Uses energy remaining after friction Increases with Discharge (amount) Velocity (speed) Turbulence (rough flow) Up to bankfull stage / flood levels In flood large wetted perimeter friction deposition SUSPENSION Fine particles clay and silt Amount + size of suspended load increases velocity and turbulence. Increases towards mouth (brown water) Greatest part of river’s load TRANSPORTATION 1

  7. Processes of Transportation

  8. SOLUTION Precipitation carbonic acid limestone. Normally dissolved or solution load is small proportion of total load (except in limestone areas) SALTATION Large bedload is lifted and bounced TRACTION Largest bedload rolls or slides along bed Proportion of bedload may be small if river not at flood level Difficult to measure TRANSPORTATION 2

  9. Load = - suspended load - dissolved or solution load - bedload Where does it come from? Material worn from bed and banks Material from weathering on valley sides River Tyne (annual) 57% suspended 35% solution 8% bedload 10 tonne every 20mins River Amazon 40 tonnes every minute Summary

  10. DEPOSITION1

  11. Deposition 2

  12. HJULSTROM CURVE (1935) • Shows relationship between particle size (competence) and velocity • Mean or critical erosion velocity curve = velocity needed to pick up (entrainment) and transport particles in suspension • Mean fall or settling velocity curve = velocity at which particles fall out of suspension and are deposited • Note: • Sand (1) is easier to pick up than finer particles (2), clay has more cohesive properties • Velocity needed to maintain particles in suspension is less than that needed to pick them up, especially true for finer particles – compare (2) & (4)

  13. HOMEWORK • Read ‘An Integrated Approach’ p.71-74 • - read it carefully and study all the diagrams • - make notes on anything you missed in class • Define the terms COMPETENCE and CAPACITY • Answer questions on Hjulstrom curve

More Related