Which geosynthetic is best for a high-flow channel?

High-Performance Turf Reinforcement Mats (HP-TRMs) or articulated concrete blocks (ACBs) are typically used, depending on the calculated shear stress values. Refer to the selection matrix (Table 2).

What is the function of an anchor trench?

An anchor trench at the crest of a slope or channel bank secures the geosynthetic, preventing it from sliding and stopping water from flowing underneath it (Clause 9).

When should I use a biodegradable versus a permanent erosion control blanket?

Use biodegradable blankets (e.g., coir, jute) for short-term protection on gentle slopes where vegetation can establish quickly. Use permanent synthetic products (TRMs) for steep slopes, high-flow channels, or where vegetation alone is insufficient for long-term stability (Clause 5).

What is tractive shear stress?

It is the force exerted by flowing water on the bed and banks of a channel. The design must ensure the selected geosynthetic has a permissible shear stress greater than the calculated tractive stress at the site.

IS 17539

: 2021

Geosynthetics - Guide for Design for Erosion Control Applications

CurrentSpecializedGuidelinesBIMGeotechnical · Geosynthetics and Ground Improvement

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This standard provides comprehensive guidelines for designing erosion control systems using various geosynthetic materials. It covers site assessment, material selection, design methodologies for slopes and channels, and installation practices to mitigate soil loss caused by water flow and surface runoff.

Provides guidelines for the design and selection of geosynthetics for erosion control applications.

Quick Reference Values

Maximum Slope for Unreinforced Vegetation2H:1V to 3H:1V

Typical Minimum Anchor Trench Depth300 mm

Typical Manning's 'n' for Turf Reinforcement Mats (TRMs)0.025 - 0.035

Permissible Shear Stress for Unvegetated High-Performance TRMapprox. 480 Pa

Typical Staple/Pin Density on a 2H:1V slope2-3 per sq.m

Key Formulas

τ = γ * R * S — Tractive shear stress in an open channel

FS = τp / τd — Factor of safety for channel lining, where τp is permissible shear stress and τd is design shear stress

Practical Notes

Proper surface preparation, including grading and removing debris, is critical for the performance of any geosynthetic erosion control product.

Anchorage details (trenches, pins, staples) are often the weakest link; pay close attention to the manufacturer's and the code's recommendations for spacing and type based on slope and soil conditions.

Most systems are designed to work with vegetation. The geosynthetic provides initial stability, while vegetation provides long-term protection and reinforcement.