(A) In order to reduce drainage-related damage and hazards, adequate natural drainage systems or stormwater management installations are required to collect and transmit stormwater flows into either existing drainage facilities or a natural drainage system.
(B) All storm drainage facilities shall be designed, constructed, and maintained so that adjacent properties are not unreasonably burdened with surface waters as a result of such improvements, specifically:
(1) Off-site areas which drain to or across a site proposed for development must be accommodated in the stormwater plans for the development. The stormwater management system must be capable of conveying the existing off-site flows through or around the development such that the volume and rate of flow from the adjacent property is not altered. If brush flows are earned in the site system any detention system shall be sized to accommodate this flow. The flow must be released to the original drainage area; and
(2) Storm drainage facilities shall be designed to limit the discharge from the site to the rate that existed prior to development of the site. For projects that are redeveloping a developed site, the discharge will be limited to that which occurs before any new development. The type and location of the discharge will be as occurred before the current development unless the discharge is to a human-made conveyance system.
(C) All site improvements shall be provided with a drainage system that is adequate to prevent the undue retention of surface water on the development site.
(D) These goals for discharge can be accomplished by designing, constructing, and maintaining all stormwater management installations to the extent practicable:
(1) Avoid increases in surface runoff volume and velocity by including measures which promote the infiltration of stormwater;
(2) Maximize the time of concentration of stormwater runoff; and
(3) Promote the filtration and precipitation of pollutants from stormwater runoff in order to protect the water quality of the receiving watercourse.
(E) Whenever practicable, the drainage system of a development site shall coordinate with and connect to the drainage systems or drainage ways on surrounding properties or streets. Permission must be received from other applicable entities for connection.
(F) To the extent practicable, all site improvements shall conform to the natural contours of the land, and without disturbance, utilize the preexisting natural and pre-existing human-made drainage ways.
(G) To the extent practicable, lot boundaries within subdivisions shall be made to coincide with natural and preexisting human-made drainage ways to avoid creation of lots that can only be built upon by altering such drainage ways.
(H) Stormwater shall not be diverted from one natural drainage basin into another.
(I) Stormwater shall not be channeled or directed into sanitarily sewers.
(J) Stormwater controls shall not be located within the designated floodway.
(K) No built upon area shall be located within 30 feet landward from any perennial and intermittent surface waters. A surface water shall be deemed present if the feature is approximately shown on either the most recent version of the soil survey map prepared by the Natural Resources Conservation Service of the U.S. Department of Agriculture or the most recent version of the quadrangle topographic maps prepared by the USGS.
(L) Streams shall not be relocated unless it is demonstrated that the relocation of the stream will have a positive impact on water quality while reducing velocity. All other applicable permits must be received.
(2013 Code, § 20-11)