Presentation on theme: "BANK PROTECTION AND WADI TRAINING Lesson 2"— Presentation transcript:
BANK PROTECTION AND WADI TRAINING Lesson 2 IanMcAnderson@aol.com
Bank protection and Wadi training High flow velocities during spates often erode Wadi banks meander patterns to develop and migrate downstream Wadi beds can be significantly lowered during the passage of large floods traditional intakes to be left stranded
Providing engineered structures to control bed levels Farmers give bank protection work a high priority training and back protection works that cause damage elsewhere River training and bank protection approached in a holistic manner
blocks Vs. crated boulders The subject has been well debated. General experience, which has served successfully for over 100 years, is to use crated boulders in alluvium deposits for launching aprons. The size of crate is determined on the basis of water velocity to prevent it being swept and lifted away.
The basic principle of the launching apron is best described as the one of a carpet which takes the shape of the scoured bed. The bottom of the apron is normally placed at LWL. It is not possible to lay the apron below knee deep water because of difficult manual working. In such cases, it is best to fill the area, if necessary by using suction dredgers
Crated boulders launch smoothly and being flexible, easily take the shape of the scoured beds and are not lost as in case of concrete blocks For pitching guide bunds, slopes also, boulders in the form of grids are used.
gabion apron Require minimal excavation and grade work. Generally the gabion apron is placed directly on the ground utilizing a geotextile filter fabric between the gabion apron soil interface to prevent and leaching of soils from underneath the apron. Gabions or reno mattresses may also be connected together filled and then placed into the water with a sling arrangement. This method is frequently used for building scour-resisting mats around bridge piers etc