A. Maintenance of Continuity. The entrance and exit points and continuity of all natural drainage channels on a lot or parcel shall be preserved. Ponding of water shall not be permitted above cut or fill slopes. Building sites must be designed to carry surface waters away from buildings and away from or through retaining walls.

B. Swale Grading. The minimum amount of swale grading necessary for drainage purposes is not subject to the restoration procedures of Subsection 5.02.B.14.

C. Character. Retained washes and new drainage channels shall be given a “natural” desert character where possible in accordance with the Town’s engineering requirements. Requirements may include landscaping with rock and native plant materials, and preservation of existing natural features (see Exhibit 26).

D. Detention Basins. Storm water detention basins with natural materials are encouraged subject to the conditions and locations as approved by the Town Engineer.

E. Detention Basin Re-vegetation/Aesthetics. Storm water detention basins shall be re-vegetated with existing vegetation and native plant materials where appropriate in accordance with the approved landscape plan. Terracing, berming and contouring will be encouraged to naturalize and enhance the aesthetics of the basin and to blend with the surrounding terrain.

F. Basin Construction. Basins shall be designed to allow for the creation of peninsulas, more “natural” contouring, and the placement of boulders and rock outcroppings (See Exhibit 27).

G. Basin Slopes. Basin slopes shall not exceed a three to one (horizontal to vertical) slope adjacent to public streets. Remaining slopes shall also not exceed a three to one slope. Deviations may be approved by the Town Engineer if the lesser slope creates excessive grading of the existing desert environment (See Exhibit 27).

H. Native Materials. The use of native materials in the construction of headwalls, flow retardant structures and devices, culverts and drainage channel bottoms is encouraged (See Exhibits 28 and 29).

I. Erosion Prevention. Erosion controls should be constructed and maintained to prevent erosion of all slopes and graded areas. Surface drainage interceptors may be provided at the top of all cut and fill slopes where surface runoff will create erosion problems. Sub-surface drainage facilities may be required for stability and protection of affected areas due to ground water seepage. Erosion protection of drainage swales will be encouraged through the use of native rocks and native plant materials. Where runoff velocities necessitate additional erosion protection, the use of integral colored gunite or alternative material may be approved by the Town Council with a recommendation by the Town Engineer and Community Development Director or designee.