Erosion control blanket and TRM, matched to the shear.

Temporary biodegradable vs permanent synthetic.

Rolled erosion control products (RECP) split into two families along the temporary-permanent axis.

• Erosion control blanket (ECB), temporary biodegradable. Coir (coconut fibre), straw, jute, or wood excelsior fibre stitched between two biodegradable netting layers. Function: protect the soil surface from rain-impact erosion and overland-flow scour during the 6-12 week vegetation establishment window; then biodegrade over 12-36 months as the vegetation root mat takes over the long-term erosion control function. Suited to slope angles up to 2H:1V (about 27 degrees) and channels with permissible shear stress below 150 Pa.
• Turf reinforcement mat (TRM), permanent synthetic. UV-stabilised polypropylene, polyethylene, or nylon formed into a three-dimensional matrix 10-25 mm thick. Function: immediate erosion protection during vegetation establishment AND permanent embedment into the vegetated root mat for sustained higher shear stress capacity. Suited to slope angles 1H:1V to vertical, channels with design shear 150-500 Pa, and any project where long design life and high-flow events are expected.

A third family, the open-weave mesh (jute, coir, polypropylene), provides a middle option for low-shear contexts where biodegradability is preferred and design life of 12-18 months suffices.

FHWA HEC-15 / 23 by the numbers.

The single number that drives RECP selection is shear stress capacity (the maximum tractive force the product can sustain at the soil surface without erosion, expressed in Pa or N/m²). FHWA HEC-15 publishes design tables; the values below are indicative for the most commonly used RECP types.

Design shear stress at site is computed from slope geometry and overland flow depth (for slopes) or channel hydraulics (for channel lining) per HEC-15 chapter 4 procedures. The product permissible shear (with vegetation cover assumed established) must exceed the design shear with a factor of safety of 1.2-1.5.

Where the RECP goes across Malaysia.

Vegetation establishment vs the wet season.

Malaysian rainfall is the dominant factor in RECP selection beyond shear stress.

• Peninsular west coast and central highlands. Year-round rainfall with peaks April-May and October-November (inter-monsoon transition). Vegetation establishment is generally favourable as the rain provides moisture; the risk is concentrated rainfall events during the establishment window that can wash out the seed mix.
• East coast (Kelantan, Terengganu, Pahang) and Sarawak. Strong northeast monsoon December-February with peak daily rainfall routinely 100-300 mm. Any slope exposed during these months without established vegetation will suffer significant erosion regardless of blanket selection.
• Sabah. Generally year-round rainfall with localised peaks; weaker monsoon character than east-coast Peninsular.

The programme rule we apply: for slopes that will be exposed during the wet season without established vegetation, upgrade the RECP to higher-density coir (700-900 gsm minimum) or to synthetic TRM with hydroseeding underneath, and on slopes steeper than 1.5H:1V add StrataWeb HDPE geocell over the blanket for immediate erosion protection. For projects with tight programmes that cannot wait for vegetation establishment, the geocell + TRM + hydroseed combination delivers immediate erosion protection alongside the ongoing vegetation establishment.

Three layers for steep slope success.

On slope angles above 1.5H:1V the blanket alone is often insufficient. The standard Malaysian solution combines three layers in sequence.

1. Layer 1: hydroseed slurry. Water plus seed mix (typically Brachiaria decumbens / signal grass plus a creeping legume for nitrogen fixation in tropical soils) plus fertiliser plus tackifier (water-soluble polymer for seed adhesion) plus mulch fibre (paper or wood). Sprayed directly onto the prepared slope at design coverage rate. The tackifier holds the seed mix to the slope face during the first weeks before germination.
2. Layer 2: erosion control blanket. Coir double-net (700-900 gsm) for routine cases, synthetic TRM for steeper / longer-life cases. Placed over the hydroseed, pinned at top with steel U-pins driven 200-300 mm into firm ground at 1.0 m centres, then pinned across the face at 1.0-1.5 m centres. The blanket protects the hydroseed from direct rain impact during establishment.
3. Layer 3: geocell facing (above 1.5H:1V). StrataWeb HDPE perforated geocell, 75-150 mm cell depth, percussion-anchored to the slope at the perimeter and at internal centres. Cells are filled with topsoil from above and the seed and vegetation establish through the cell openings into the underlying blanket-soil interface. The cell provides cellular reinforcement that resists fill slumping during the 6-12 week establishment window and remains permanently embedded in the root mat.

The three-layer combination is the standard for hillside township slopes above 1.5H:1V and for any slope where the construction programme overlaps with the wet season. See our geocell slope stabilisation page for the geocell detail.

From topsoil prep to handover.

1. Topsoil preparation. Strip and stockpile native topsoil during slope formation; replace at 75-150 mm depth on the prepared slope face. Light tracking (do not over-compact) to provide a firm seedbed.
2. Hydroseed application. Spray hydroseed slurry at design coverage rate (typically 1500-2500 litres per hectare of dilute slurry). Apply on a dry day to minimise wash-out before tackifier sets.
3. RECP placement. Unroll the blanket parallel to the slope contour, top-pin first with steel U-pins driven 200-300 mm into firm ground at 1.0 m centres along the top edge. Roll down the slope face, smoothing as you go to ensure full soil contact (any air gap behind the blanket reduces effectiveness).
4. Pin pattern. Across the face at 1.0-1.5 m centres on both flat and steep slopes; tighter centres (0.5-1.0 m) on steeper slopes and at channel applications. At blanket overlaps, pin through both layers.
5. Toe anchorage. Trench the toe of each blanket roll 150-300 mm into the foundation soil; tuck the blanket end into the trench and backfill. Prevents flow scour from undermining the toe.
6. Geocell overlay (if specified). Lay StrataWeb panels over the blanket, percussion-anchor at perimeter and at internal centres per the geocell installation procedure. Fill cells with topsoil from above.
7. Vegetation establishment monitoring. 6-12 weeks under regular monitoring; supplementary hydroseed application to any bald patches; supplementary watering during dry spells. Vegetation should reach 70 percent cover by the end of the establishment window.
8. Handover documentation. Hydroseed mix and application record, RECP delivery certificate, pin pattern and anchorage record, vegetation establishment certificate at completion.

Combined slope scope.