Under which conditions is a stormwater management plan required?

A stormwater management plan is required when new development or redevelopment disturbs one acre or more because this threshold is established by regulatory agencies to address potential adverse effects on water quality and quantity due to increased impervious surfaces. The rationale behind this requirement is that projects disturbing this amount of land are likely to produce significant amounts of stormwater runoff, which can contribute to erosion, sedimentation, and the introduction of pollutants into water bodies.

The need for a stormwater management plan is part of broader efforts to protect water resources, manage flooding, and ensure that developments are designed to control runoff effectively. When the disturbed area is one acre or more, it can lead to substantial hydrological changes in the landscape, making this threshold an important criterion for requiring a formal plan.

This requirement is tied to the regulations that govern stormwater management at both state and local levels, intending to minimize environmental impacts and promote responsible land use planning.