Gully erosion

its gully erosion wdg

1. SWE 112 SOIL AND WATER CONSERVATION OF ENGINEERING (1+1) GULLY EROSION ANGEL A 2020048013 COURSE TEACHER Ms. M. Limna Jasika Banu, AP ( Agrl . Engg . )

2. GULLY EROSION Gully erosion is the removal of soil by running water with the formation of channels that can not smoothed out completely by normal cultivation. It is the advanced stage of rill erosion, much as rill erosion is advanced stage of sheet erosion. Rills are small in size and can be destroyed by tillage operations. If rills are not destroyed, the rills become larger in size and shape due to prolonged occurrence of flow through them and cannot be removed by tillage operations and these are called gullies.

3. GULLY EROSION Gullies unless stopped or controlled in the rill stage will get deepened and widened. High intensity of flow of the run off increase the gully dimensions. Cattle paths, cart tracks, dead furrow, tillage furrow, or other depressions down a slope favour concentration of water. Large gullies and their network are called as ravines. The rate of gully erosion mainly depends on the run off characteristics of the watershed, namely watershed area, soil characteristics.

4. GULLY EROSION

5. Causes of gully erosion Gully erosion may occur as a result in continuous and heavy rainfall The greater the intensity and duration of a rainfall, the higher and erosion potential. The impact of raindrops on the soil surface can break down soil sediments and disperse the sediment to down streams. It caused by mining activities. It is also caused by farming and uncontrolled grazing practices,it breaks up soil and softens the overall structure.

6. STAGES OF GULLY DEVELOPMENT FOUR STAGES OF GULLY DEVELOPMENT ARE GENERALLY RECOGNISED. STAGE 1 : FORMATION STAGE STAGE 2 : DEVELOPMENT STAGE STAGE 3 : HEALING STAGE STAGE 4 : STABILIZATION STAGE

7. STAGE 1 FORMATION STAGE Initiation of gully erosion Channel erosion Deepening of gully bed Depends on top soil & other factors This stage proceeds slowly if top soil is resistant

8. STAGE 2 DEVELOPMENT STAGE Major formation of the gully and erosion takes place Upstream movement of the gully head Enlargement of gully in width and depth Gully banks are eroded to maximum and width becomes maximum Gully cuts to C-horizon and parent material is removed rapidly

9. STAGE 3 HEALING STAGE Local vegetation starts growing in the gully and get stabilized No significant erosion in any form from gully section Healing process starts

10. STAGE 4 STABILIZATION STAGE Last stage of gully development Gully gets fully stabilised Gully reaches a stable gradient Sufficient vegetation cover develops over the gully surface to anchor the soil and permit development of new top soil No further development of gully unless healing process is disturbed

11. CLASSIFICATION OF GULLY BASED ON THE Shape of the gully( U shape , V shape ) State of the gully (nature ) Dimension of the gully ( depth, width and side slopes)

12. BASED ON SHAPE BASED ON THE SHAPE OF THEIR CROSS SECTIO OF THE GULLY U SHAPED V SHAPED

13. BASED ON SHAPE U SHAPED V SHAPED Found in alluvial plain where surface and sub-surface soil are easily erodible Runoff flow undermines and gully banks collapse Formation of vertical side walls in U shape Where sub-soil are tough to resist the rapid cutting of soil by runoff flow Resistance to erosion increases with depth Common in hilly regions accompanied with steep slope

14. BASED ON STATE ACTIVE AND INACTIVE STAGE Active gullies ate those which continued to enlarge and they will be recognized by the presence of loose soils. Inactive gullies are that which does not enlarge further and is covered with vegetation on the side slopes.

15. BASED ON DIMENSION

16. Small Gully : Can easily be crossed by farm implements Removed by ploughing and smoothing operations By stabilizing the vegetation Medium Gully : Cannot be easily crossed by farm implements Can be controlled by terracing and ploughing operations Sides are stabilised by creating vegetation on them Large Gully : Cannot be reclaimed Tree planting is done as an effective method

17. STREAM BANK EROSION Serious hazard in drainage lines and river courses in India and other countries. In India, it is serious in the Himalayan region Indo Gangetic Plains, The Brahmaputra Valley, and in the Plateau region, especially in the black soil areas. Natural process that occurs when the forces exerted by flowing water exceed the resisting forces of bank materials and vegetation.

18. STREAM BANK EROSION

19. CAUSES When a stream is straightened or widened, stream bank erosion increases. Damaging or removing streamside vegetation to the point where it no longer provides for bank stability can cause a dramatic increase in bank erosion. Heavy rainfall – soil can be eroded by heavy and excessive rainfall. Housing near bank causes the river bank erosion .

20. USDA, SCS, Agriculture Handbook No. 61 (1954). A Manual on Conservation of Soil and Water, Handbook for Agricultural Workers. USDA, Washington, D.C. 208 p. LINK ADDRESS http://ecoursesonline.iasri.res.in/mod/page/view.php?id=2103 https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/gully-erosion#:~:text=Gully%20erosion%20(Fig.,dependent%20on%20the%20rock%20type . Reference