Which structural weakness arises when a Roman castrum wall's foundational drainage system fails due to silt accumulation?

💡 Explanation

When drainage fails, hydrostatic pressure increases along the wall's foundations because water saturates the soil, leading to differential settling and compromised soil-bearing capacity, causing localized wall subsidence. Therefore wall subsidence occurs, rather than gatehouse instability, rampart reduction, or battlements coverage which result from different compromising mechanisms in the fortress construction.

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