Which risk increased for Roman legions when road construction involved bridging seasonally-flooded floodplains?

💡 Explanation

When bridging floodplains, seasonally high water flows induce scour erosion because high-velocity currents remove sediment around bridge foundations, weakening support. Therefore, the risk of undermining increases, rather than ambushes, shortages, or unrest, which involve logistical, tactical, or social factors during construction in settled areas.

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