Calvert County, MD Landscaping Rules: Rainwater Harvesting (2026)

Section 123-11 requires that a developer demonstrate Environmental Site Design has been implemented to the maximum extent practicable before any structural best management practice is considered, tying back to the minimum control requirements of § 123-10, which are met only when channel stability is maintained, predevelopment groundwater recharge is replicated, and nonpoint source pollution is minimized. Among the ESD treatment practices the section lists for satisfying those requirements is rainwater harvesting, alongside disconnection of rooftop runoff, submerged gravel wetlands, infiltration berms, drywells, micro-bioretention, rain gardens and swales (§ 123-11(A)(2)).

These practices must be designed to the specifications of the 2000 Maryland Stormwater Design Manual incorporated by reference in § 123-2, and the phased plans that select them go through concept, site development and final construction review by the Department under § 123-13. Once ESD practices such as rainwater harvesting are used to satisfy a project's stormwater management plan, § 123-11(C) requires that they be recorded in the Calvert County land records and remain unaltered by later property owners; the Department of Public Works must approve any alteration before it happens.

The chapter targets new development and redevelopment; minor additions to an existing single-family home, and projects disturbing 5,000 square feet or less, are exempt from the stormwater management requirement altogether (§ 123-6), so a rainwater harvesting system installed on an existing home outside a covered project is not independently regulated by this chapter.