Presentation of Gully Erosion control measurements

Discuss types of gully control measures. Only engineering measures are discussed in detail.

1. Gully Control Measures By:- Er . Gurpreet Singh

2. Gully Control Measures Source:- Google, notes and Books

3. Design of Permanent Structure The design of the gully erosion control structure involves Hydrologic design Hydraulic Structural Design

4. Permanent Structure Three Basic type of permanent structures that are employed for stabilizing gullies Drop spillway Drop inlet spillway Chute spillway Used in gullies with medium to large drainage area, i.e in situations where temporary structure may fail. Usually built of masonry or reinforced concrete. Proven measures for efficieny erosion control in any soil and conservation program. Source: Books

5. Inter-comparison Drop-spillway: Drop < 3m upstream storage – No Drop-inlet spillway Drop > 3 m upstream storage – Yes Chute Spillway > 3m upstream – No Source: Books, google

6. Functions The should handle the peak runoff at safe velocity. The should be able to stabilize the gully. The should store the water for irrigation and other purposes. The sediment flow should be controlled.

7. Purpose of designing Gully Control Gully stabilisation Soil erosion control Sediment Control Water conservation Flood control Drainage

8. Planning for Design Permanent structure are constructed when the benefits from such structures are justification compared to the cost of construction. The design after careful investigation of Various factors influencing the characteristics of runoff The downstream flow characteristic Other specific requirement An analysis of all the factors affecting the work. No standard solution which applied for all problems

9. Drop Spillway It is a weir structure, in which flow passes through the weir opening, falls on the apron and then passes in to the downstream. Source: Books, google

10. Functions of components Head wall : It acts as a front wall against runoff in the drop spillway . The size of the weir should be sufficient to pass the design discharge safety. Head wall extension: Permit stable fill and prevents piping. Sidewall: Guide the water and protect the fill against erosion. Wing wall: Provide stability to fill and give protection to gully bank and surface. Apron: Dissipates the kinetic energy of falling water by creating hydraulic jump. Longitudinal skill: Provide stability to the apron. End sills: Its main function is to obstruct the water from going directly into the channel below. Cut-off wall: Prevents piping under the structure besides reducing uplift and preventing sliding. Toe wall: Prevents undercutting of apron. Source: Books

11. Use of drop spillway To control gradient in either natural or constructed channel. To serve as reservoir spillway where the total drop in relatively low. To control tail-water at the outlet of a spillway or conduit. To serve as inlet and outlet structures for tile drainage system.

12. Drop-Inle t Spillway Where the inlet is funnel shaped this type of structure is often called as Morning glory/Glory hole. Discharge Characteristics Discharge characteristics varies with the range of head . As long as the outflow through the box remains less than the capacity of pipe. When the outflow at the box exceeds the capacity of the pipe, the box inlet fills and the discharge is then governed by the pipe capacity.

13. Advantages Stability It is very stable structure and likelihood of serious structural damage is remote. Non-clogging of weir Rectangular weir, which is used in this case Ease & economy of construction. Low maintenance cost. Standardization. Disadvantages Maximum drop is limited to 3m It is not a favourable structure where temporary spillway storage is desired to obtain large reduction in the discharge.

14. Chute Spillway A chute spillway is a steeply sloping open channel, which leads the water from a channel, which leads the water from higher elevation to the downstream. The chute is sometimes of constant width but is usually narrowed for economy and they widened near the end the reduced the discharge velocity. The slope of the chute must conform to the slope at the site, longitudinal and cross section survey at the site. Applicability Used when the drop exceed 3 m Superior to drop-inlet spillway for large discharge. Preferred over drop-inlet spillway when there is no opportunity to provide temporary storage.

15. Disadvantage There is a considerable danger of undermining due to additional precaution are required to handle this problem. In poorly drained areas, there is a problem of seepage Such areas may not be suitable for chute spillway as seepage tends to weaken foundation Constructing chute spillway is essential and no other substitutes are available.

16. Temporary Gully It is for gully control, construction of brush, wood, rocks, woven wire and sod/earth. It is used where material locally available and labour is cheap. It is helpful during the establishment of vegetation. Main purpose to control the erosion It is suitable with small drainage areas. Helpful for collecting soil and conserve moisture in guly bottom for the growth of vegetation. A grade of 0.1 to 0.5% is provided.

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