Standing on a coastal road carved into a steep seaside slope, it is easy to forget how much engineering goes into keeping the land from sliding into the sea. Beneath the greenery and behind those patterned concrete walls lies a clever solution that has quietly shaped coastlines and highways around the world, i.e. the crib wall – an ingenious wall blending in with nature. Simple, strong and surprisingly elegant, crib walls have been holding back soil and waves for over a century.

A little bit of history

The idea of the crib wall goes back to the early 1900s, when railway and road engineers needed a fast and reliable way to hold back earth on steep slopes. Initially, they built wooden cribs, with stacks of interlocking logs or beams forming open boxes, which were then filled with stones. These early versions were cheap and easy to build using local timber.

As concrete became more common in the mid-20th century, engineers replaced timber with precast concrete units. This made crib walls stronger, more durable and easier to build in standard sizes. By the 1970s, crib systems had spread across Europe, North America and Asia, appearing along highways, rivers and even the edges of the sea.

Where in the world?

Crib walls quietly work in some of the world’s most dramatic coastal settings, adapting to challenges like salt spray, heavy rain, unstable rock and traffic loads.

In Hong Kong, they protect steep mountain roads from landslides and typhoon runoff. Along Australia’s Great Ocean Road, they stabilise cliff edges; while in Cornwall and Wales, modular systems like Permacrib reinforce railway embankments and coastal paths. In California, crib walls combined with geogrids improve earthquake resistance while maintaining effective drainage.

Anatomy of a crib wall: Parts and mechanism

A crib wall is essentially a 3-dimensional, interlocking structure designed to hold back soil while allowing natural drainage. It is made up of a series of box-like cells, created by stacking precast concrete or timber beams in a crisscross pattern. These cells are then filled with crushed stone, gravel or other free-draining material. The infill provides the wall’s weight, which is critical for resisting the lateral pressure of the soil behind it.

The open-cell design is more than structural, for it also serves as a natural drainage system. Water from rainfall or seepage flows freely through the stone-filled cells, preventing hydrostatic pressure from building up behind the façade, which is a common cause of retaining wall failure.

You may notice that a crib wall is usually constructed with a slight backward lean, or batter, into the slope. This angled design is not just aesthetic, for it helps the wall resist the sideways pressure of the soil behind it. The weight of the stone-filled cells, combined with the friction between them, works together to anchor the structure firmly in place.

The interlocking pattern of the crib units also provides a measure of flexibility, allowing the wall to adjust slightly to natural ground movements, minor soil settlement or even wave action along coastal slopes. This combination of stability and adaptability means the wall can absorb stresses without cracking, making it particularly effective in challenging environments where water, soil and shifting loads interact, such as in an earthquake event.

Why they work so well by the sea

Building near the ocean also presents unique challenges: Saltwater, waves and shifting soils can quickly compromise conventional retaining walls. Crib walls are particularly well-suited to these conditions because their open, interlocking design allows water and wave energy to pass through rather than exerting full pressure on the structure. This reduces erosion and soil washout while maintaining slope stability.

The modular, stone-filled cells also encourage vegetation to establish naturally, which reinforces the soil and gradually integrates the wall into the coastal landscape. Additionally, the ability to use locally sourced materials, such as coastal rock or recycled concrete, makes crib walls a sustainable choice, reducing both costs and environmental impact. Taken together, crib walls deliver both strength and sustainability for safeguarding coastal slopes.

Engineering meets ecology

Building on their natural strengths, today’s crib walls go beyond stone and concrete. Modern systems use eco-friendly materials like recycled plastic or geopolymer concrete, while “green crib walls” are living structures filled with soil and planted with native vegetation, restoring habitats and blending into the landscape. Increasingly, crib walls are part of “living shoreline” projects, paired with vegetation, reefs or rock berms to absorb wave energy and shelter marine life. The goal is no longer just to resist nature, but to work with it, creating resilient and environmentally harmonious coastal protection.

A quiet hero of geo-engineering

Crib walls rarely steal the spotlight. They do not soar like bridges or gleam like steel towers, yet they form an unseen backbone protecting roads, railways and coastal communities. They strike a rare balance between engineering and nature – heavy enough to hold soil, permeable enough to manage water, and subtle enough to blend into the landscape.

Hence, from timber boxes to green living walls, crib structures have evolved without losing their purpose. On every seaside slope they stabilise, quietly showing that sometimes the best way to withstand nature is not to fight it, but to work with it.

-- BERNAMA

Prof Ir Dr Chan Chee Ming is Principal Researcher of the Research Centre for Soft Soils (RECESS) at the Faculty of Engineering Technology, Universiti Tun Hussein Onn Malaysia (UTHM).