What is the main purpose of a check dam as per this code?

Primarily for soil conservation, gully control, and groundwater recharge, not for significant water storage.

What return period is recommended for the design flood?

Generally 10 to 25 years, depending on the importance of the structure and downstream risk (Clause 3.2).

What formula is used for spillway discharge?

The broad-crested weir formula, Q = C * L * H^(3/2), is typically used for the spillway section (Clause 4.2).

Why are energy dissipation works important?

To prevent scouring and undermining of the dam's foundation at the downstream toe, which is a common failure mode (Clause 6).

IS 11521

: 1985

Criteria for Hydraulic Design of Check Dams

CurrentSpecializedGuidelinesWater Resources · Irrigation and Canal Structures

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This standard provides guidelines for the hydraulic design of small check dams used for soil conservation, gully control, and groundwater recharge. It covers the estimation of design flood, hydraulic design of the spillway and body wall, requirements for downstream energy dissipation, and determination of freeboard.

Lays down criteria for the hydraulic design of check dams for soil conservation and erosion control.

Quick Reference Values

Typical Design Flood Return Period10 to 25 years

Minimum Freeboard over Max Water Level0.3 m

Discharge Coefficient (Cd) for Masonry/Concrete Weir (Metric)1.7

Maximum Height generally considered< 3.0 m

Key Formulas

Q = C * L * H^(3/2) — Discharge over a broad-crested weir (spillway)

Practical Notes

This standard focuses on hydraulic design. Structural stability (overturning, sliding) and foundation analysis (seepage, piping) must be checked separately.

Selection of the site is crucial for effectiveness and should be based on gully characteristics, catchment area, and foundation suitability.

Inadequate spillway capacity and lack of proper energy dissipation are the most common causes of check dam failure; pay close attention to Clauses 4 and 6.