Which hydrologic runoff characteristic remains unchanged by post-development?

In the context of hydrology and land development, it's important to recognize how various factors change due to urbanization or alteration of natural landscapes. The characteristic that remains unchanged following post-development conditions is notably the volume of runoff. This is because while development can affect peak flow rates and runoff coefficients—two aspects that are highly influenced by factors such as land cover, soil type, and watershed characteristics—the total volume of runoff for a given storm event is largely determined by the rainfall amount and the watershed area.

When changes in land use occur, they can lead to increased impervious surfaces, altering how quickly water reaches downstream areas (thus affecting peak flow rates) and changing the runoff coefficient, which is a measure used to predict runoff amounts based on land surface characteristics. However, these changes may not necessarily increase or decrease the total volume of runoff produced during a specific rainfall event.

Hence, the total volume remains consistent when considering the same rainfall event, regardless of the development. This understanding is crucial in water resource management, particularly when designing stormwater management systems that consider the implications of urbanization on hydrology.