17.32.280 Storm drainage and flood plans.
1. Complete drainage systems for the entire subdivision area shall be designed by a professional engineer, licensed in the state and qualified to perform such work, and shall be shown graphically. All existing drainage features which are to be incorporated in the design shall be so identified. If the final plat is to be presented in sections, a general drainage plan for the entire area shall be presented with the first section, and appropriate development stages for the drainage system for each section indicated.
2. The drainage and flood plan systems shall be designed to:
a. Permit the unimpeded flow of natural water courses;
b. Ensure adequate drainage of all low points;
c. Meet the requirements as established in Chapter 17.62 – Flood Damage Prevention;
d. Any contemplated flood plain encroachment or channeling shall be thoroughly analyzed and its effect on stream flow determined before such encroachment is undertaken. Any construction, dumping, and filling operations in a designated flood-way constitute an encroachment and must be approved by the planning commission before accomplishment;
e. No lot one (1) acre or less in area shall include flood-lands. All lots more than one (1) acre shall contain not less than forty thousand (40,000) square feet of land which is at an elevation at least two feet (2') above the elevation of the one hundred (100) year recurrence interval flood, or, where such data is not available, five feet (5') above the elevation of the maximum flood record;
f. Consider the drainage basin as a whole and shall accommodate not only runoff from the subdivision area but also, where applicable, the system shall be designed to accommodate the runoff from those areas adjacent to and “upstream” from the subdivision itself, as well as its effects on lands downstream;
g. All proposed surface drainage structures shall be indicated on the plans;
h. All appropriate designs, details, and dimensions needed to clearly explain proposed construction materials and elevations shall be included in the drainage plans. (Ord. 2023-22 §1, renumbered, 2023; Ord. 2001-8, amended, 2001; Ord. 111 §1, amended, 1985; Prior code §12-107-7(I). Formerly 17.32.310)