Stormwater management shall be accomplished for all new development according to the minimum requirements established in this section and the Design Manual as follows:
All planning techniques, nonstructural practices, and design methods specified in the Design Manual shall 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. Stormwater management 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. The MEP standard is met when channel stability is maintained, predevelopment groundwater recharge is replicated, nonpoint source pollution is minimized, and structural stormwater management practices are used only if determined to be absolutely necessary.
Control of the ten-year frequency storm event is required according to the Design Manual. The approving authority may determine that additional stormwater management is necessary because historical flooding problems exist in the vicinity of the proposed development or redevelopment and the development of the applicant's property or already existing on the applicant's property contributes to such flooding problems.
The approving authority may require more than the minimum control requirements specified in this chapter if hydrologic or topographic conditions warrant or if flooding problems exist in the vicinity of the proposed development or redevelopment and the development of the applicant's property or already existing development on the applicant's property contributes to such flooding problems.
Alternate minimum control requirements may be adopted subject to approval by the Maryland Department of the Environment. The Maryland Department of the Environment shall require a demonstration that alternative requirements will implement ESD to the MEP and control flood damages, accelerated stream erosion, water quality and sedimentation. Comprehensive watershed studies may also be required.
Stormwater management 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 to the extent achievement of consistency will not result in a regulatory taking for which just compensation is owed to the applicant.
The ESD planning techniques and practices and structural BMP established in this chapter and the Design Manual shall be used, either alone or in combination in a stormwater management plan. The applicant shall demonstrate that ESD has been implemented to the MEP before the use of a structural BMP is considered in developing a stormwater management plan.
ESD techniques and practices.
The following planning techniques shall be applied according to the Design Manual to satisfy the applicable minimum control requirements established in Article V, § 192-12, of this chapter:
The following ESD practices shall be designed according to the Design Manual to satisfy the applicable minimum control requirements established in Article V, § 192-12, of this chapter.
Disconnection of rooftop runoff;
Disconnection of non-rooftop runoff;
Sheetflow to conservation areas;
Rainwater harvesting, including rain barrels, rainwater tanks, and cisterns;
Submerged gravel wetlands;
Enhanced filters; or
Any practice approved by the Maryland Department of Environment.
Requirements in the Zoning Ordinance for Rock Hall, Maryland, or in other ordinances of the Town of Rock Hall regulating development will not excuse implementation of ESD to the MEP. As the Town of Rock Hall implements this chapter, the Mayor and Council will evaluate provisions in the Zoning Ordinance or other ordinances or development requirements as necessary or appropriate in order to eliminate or mitigate impediments to implementing ESD to the MEP according the Design Manual.
Structural stormwater management measures.
The following structural stormwater management practices shall be designed according to the Design Manual to satisfy the applicable minimum control requirements established in Article V, § 192-12, in this chapter:
When selecting structural stormwater management practices, the applicant shall consider the performance criteria specified in the Design Manual with regard to general feasibility, conveyance, pretreatment, treatment and geometry, environment and landscaping, and maintenance.
Structural stormwater management practices shall be selected to accommodate the unique hydrologic or geologic conditions in the Eastern Shore.
Alternative practices and measures. Alternative ESD planning techniques and treatment practices and structural stormwater measures may be used for new development runoff control if the practices and measures meet the performance criteria in the Design Manual and all subsequent revisions and are approved by the Maryland Department of Environment. Practices used for redevelopment projects shall be approved by the approving authority.
Recordation of practices and measures. ESD techniques and treatment practices and structural stormwater management measures used to satisfy the minimum requirements in Article V, § 192-12 of this chapter must be recorded in the land records of Kent County and remain unaltered by subsequent property owners. Prior approval from the approving authority shall be obtained before any stormwater management practice is altered.
Modification. For purposes of modifying the minimum control requirements or design criteria, the applicant shall submit an analysis to the approving authority of the impacts of stormwater flows downstream in the watershed. The analysis shall include hydrologic and hydraulic calculations necessary to determine the impact of hydrographic timing modifications of the proposed development upon a dam, highway, structure, or natural point of restricted stream flow. The point of investigation shall be established with the concurrence of the approving authority, downstream of the first downstream tributary whose drainage area equals or exceeds the contributing area to the project or stormwater management facility.
Specific design criteria. The basic design criteria, methodologies, and construction specifications, subject to the approval of the approving authority and the Maryland Department of Environment shall be those of the Design Manual.