unfordable

Unfordable is an adjective used to describe a river, stream, or other watercourse that cannot be crossed by fording at a given location and set of conditions. A ford is a shallow place where a river can be crossed by pedestrians or vehicles without a bridge. When a crossing is not possible, the watercourse is described as unfordable. The term is most common in travel writing, field guides, and physical geography, though it is not a formal category in modern hydrology.

Crossing feasibility depends on multiple factors: water depth and width, current velocity, bed and bank stability, water temperature, weather and seasonal changes, debris or ice, and the type of crossing equipment or vehicle. A ford that is safe at one time may become unfordable after rainfall, snowmelt, or flood events. Conversely, a previously unfordable section may become reachable if water recedes or after construction of a bridge.

In practice, cartographers and expedition planners use the concept to indicate where ground-level crossings exist or do not, often marking potential fording points and noting seasonal or weather-related inaccessibility. The term contrasts with fordable, meaning a crossing is usable under expected conditions, or with infrastructure like bridges and ferries that provide permanent crossings.

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