What does the Virginia Runoff Reduction Method rely on for load calculations?

The Virginia Runoff Reduction Method utilizes land cover type and soil type in its load calculations because these factors significantly influence how water moves through the landscape and how much runoff is generated during precipitation events.

Land cover type refers to what is on the ground, such as buildings, vegetation, and impervious surfaces. Different land cover types have varying abilities to absorb water and reduce runoff. For example, forested areas typically absorb more water compared to concrete surfaces, which contribute to higher runoff volumes.

Soil type is equally important, as different soils have varying capacities for infiltration and retention of water. Sandy soils may drain quickly but retain less water, while clay soils hold more water but drain more slowly. This characteristic impacts how much stormwater can be managed on-site before it contributes to runoff.

Together, land cover and soil type provide a comprehensive understanding of the hydrologic response of a given area, which is essential for effective stormwater management and compliance with Virginia regulations. This method emphasizes a holistic approach to managing runoff by considering both the physical and ecological characteristics of the landscape.