Located within areas of special flood hazard established in section 4-4-7 of this chapter are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters which carry debris, potential projectiles and erosion potential, the following provisions apply:
A. Encroachments, including fill, new construction, substantial improvements and other development, are prohibited unless a hydraulic analysis has been performed and certified by a professional engineer in the State of Idaho as follows:
1. The hydraulic analysis shall determine and document that improvements in the floodway will not obstruct flood flows and will not result in a rise in base flood elevation upstream or adjacent to the site.
2. The hydraulic analysis shall determine and document that grading, channel improvements, bridge and culvert replacements that remove an obstruction do not cause increases in downstream flood flows.
3. The Floodplain Administrator may make the encroachment determination for minor projects, such as projects that do not increase the natural grade (e.g., paving a driveway or parking lot at existing grade open fences and small isolated obstructions such as mailbox or telephone pole).
B. If subsection A of this section is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this section 4-4-9. (Ord. 567, 4-23-2012)