In the following instances, approval is required by the
department for any development including construction, maintenance, and use of
a structure, dam, obstruction, deposit, excavation or flood control work on a
regulated floodplain or floodway unless the project is otherwise approved by a
delegated community's local floodplain ordinances adopted pursuant to
567-71.2 (455B) or is exempt
under 567-71.4 (455B).
(1)
Rural areas. In rural
areas, projects in or on the floodplain of any stream draining ten or more
square miles at the downstream end of the project site.
(2)
Urban areas. In urban
areas, projects in or on the floodplain of any river or stream draining two or
more square miles at the downstream end of the project site.
(3)
Protected streams. On
protected streams, channel changes at any location on any river or stream
designated as a protected stream pursuant to Division III of 567-Chapter
72.
(4)
Buildings and other
structures adjacent to or downstream from impoundments. For new
construction, additions, lowering, or reconstruction of buildings, water and
waste water treatment facilities, sanitary landfills, animal feeding operation
structures, or other miscellaneous structures and associated fill, without
regard to the size of the drainage area, if:
a. The project is adjacent to an impoundment
and the lowest floor level, including any basement, is lower than the top of
the adjacent dam; or
b. There is an
upstream dam and flooding can be reasonably anticipated from principal or
emergency spillway discharges; or
c. There is an upstream dam that does not
substantially comply with high hazard criteria in these rules and where
flooding can be reasonably anticipated from overtopping and failure of the
dam.
(5)
Dams. For construction, repair, or modification of any dam
that exceeds the thresholds under
567-73.3 (455B).
