Water dynamics in civil engineering: The silent spiller
The dynamics of water movement pose serious structural risks to buildings and infrastructure – and understanding these dynamics is key to avoiding costly, destructive issues, according to a recent thought piece from HKA expert Edward Poon.
“Water can act as both architect and stealth saboteur," writes Poon, a director at the risk and disputes consulting firm. “It has the power to support or destroy foundations, infiltrate the bones of buildings, and compromise structural integrity if not factored into site planning with thorough technical expertise and foresight.”
Once rain hits the ground, its behavior can vary dramatically. “A downtown block may shed 90% of rainfall as runoff,” Poon notes in the thought piece, “but a less developed landscape with more vegetation might absorb 90% of it back into the earth.”
Soil composition is pivotal. Not all ground handles water the same way: gravel drains almost instantly while clay causes water to pool – and can lead to swelling and shrinkage that undermines foundations.
Poon says the ideal soil composition for structural bearing capacity is a mixture of various soil types called “engineered granular fill” – providing strength, drainage, and resistance against settlement.
The thought piece identifies several major water-related threats that can silently undermine buildings, and some common engineering solutions to counter them.
One is seasonal ground movement. When saturated soils freeze, they expand by 9%, creating forces that can snap concrete footings and lift fence posts by four inches in a single season. In summer, clay soils dry and crack and can cause buildings to tilt – the Leaning Tower of Pisa among them.
Building deep foundations below the frost layer can mitigate surface soil drying as well as frost heaving. A drainage layer can also mitigate frost heaving, while reinforced footings can resist uplift forces.
Another threat is rising water tables. Coastal groundwater levels are climbing alongside sea levels and exerting significant uplift pressure on foundations. The absence of adequate drainage or waterproofing systems in this case can cause serious structural damage, Poon says.
Foundation drainage, reinforced footings, and deep foundations are also key engineering solutions here. Alternately, structures can be built above the high water table by raising the grade or elevating the structure.
One more threat is ground sinking and settling. Pumping large amounts of groundwater compresses aquifer layers, causing subsidence – or sinking/settling. The compression of aquifers means Mexico City sinks nearly two inches annually and Venice sinks two millimeters annually.
To combat subsidence, buildings can be supported on deep foundations on denser soils, or cement can be injected into the soil to provide a stiffer base of support.
“Whether it is directing runoff away from foundations, choosing the right soil for proper drainage, or protecting concrete against freeze-thaw cycles, the best solutions work with water’s forces, not against them,” Poon concludes. “As climate change brings heavier rains and more extreme droughts, these strategies are not just smart – they are essential for building resilient, long-lasting structures.”
