Minnehaha County, SD Environmental Rules: Grading & Drainage (2026)

Minnehaha County's authority over grading and drainage flows from SDCL Chapter 11-2 (county zoning) and SDCL Chapter 11-3 (subdivision regulation). New plats reviewed by the Minnehaha County Planning Commission must demonstrate adequate stormwater management, finished-grade design, and drainage easements to the satisfaction of the County Highway Engineer. Within Special Flood Hazard Areas mapped on FEMA FIRMs, any fill, grading, or excavation requires a Floodplain Development Permit under the county Floodplain Management Ordinance (consistent with 44 CFR 60.3) and may not increase base flood elevation by more than one foot in non-floodway areas and not at all in the regulatory floodway. The county does not impose a uniform grading-permit threshold (cubic-yard based) for single-lot work outside SFHAs and outside plat review — most rural land-leveling is unregulated at the county level, though state stormwater permitting kicks in at the one-acre disturbance threshold (SD DANR Construction General Permit). Drainage between private properties is governed by South Dakota's civil-law rule of drainage, as articulated by the SD Supreme Court (Thompson v. Andrews, 165 N.W. 9, 39 SD 477 (1917) and progeny): the upper landowner has a natural easement for the natural flow of surface water, but cannot artificially concentrate or divert water to increase the burden on the lower landowner. Disputes are civil matters litigated in circuit court. Within Sioux Falls, Brandon, Hartford, and other incorporated cities, the city code (and adopted IRC/IBC grading provisions) controls.