(A) The minimum control requirements established in this section and the Design Manual are as follows:
(1) The county shall require that the planning techniques, nonstructural practices, and design methods specified in the Design Manual be used to implement ESD to the MEP. The use of ESD planning techniques and treatment practices shall be exhausted before any structural BMP is implemented. SWM plans for development projects subject to this chapter shall be designed using ESD sizing criteria, recharge volume, water quality volume, and channel protection storage volume criteria according to the Design Manual and the Supplement. The MEP standard is met when channel stability is maintained, predevelopment groundwater recharge is replicated, nonpoint source pollution is minimized, and structural SWM practices are used only if determined to be absolutely necessary.
(2) Control requires adequate stormwater facilities and drainage systems to capture, convey, and manage the design storm peak. Control of two- and ten-year frequency storm events is required according to the Design Manual and the Supplement if the county determines that either:
(a) Historic documentation of immediate downstream flooding or channel instability problems;
(b) Neither a FEMA floodplain nor adequate continuous recorded floodplain easements exist; or
(c) Floodplain development or conveyance systems are uncontrolled.
(3) The county may require more than the minimum control requirements specified in this chapter if downstream flooding problems or danger to health and safety or damage to property or the environment exist or may be created by runoff from the development. When the county determines that there are existing buildings within the floodplain or undersized hydraulic structures immediately downstream of a project, management of the runoff from the 25-, 50-, and 100-year design storm events or greater will be required as appropriate.
(B) Alternate minimum control requirements may be adopted subject to Administration approval. Prior to approval, the Administration shall require a demonstration that alternative requirements will implement ESD to the MEP and control flood damages, accelerated stream erosion, water quality, and sedimentation. The Administration may also require comprehensive watershed studies.
(C) SWM and development plans, where applicable, shall be consistent with adopted and approved watershed management plans or flood management plans as approved by the Maryland Department of the Environment in accordance with the Flood Hazard Management Act of 1976.
(2004 Code, § 191-10) (Ord. 01-12, passed 9-27-2001; Ord. 04-07, passed 4-1-2004; Ord. 2010-05, passed 4-29-2010; Ord. 2018-11, passed 11-29-2018)