567—71.9 (455B) Stream bank protective devices. Approval by the department for construction, operation, and maintenance of stream bank protective devices (including wing dikes, jetties, et cetera) shall be required in the following instances:
	 71.9(1)  Rural areas. In rural areas:
	  a.   	 All stream bank protective devices along any river or stream draining more than 100 square miles.
	  b.   	 Stream bank protective devices along any river or stream draining between 10 and 100 square miles where the cross-sectional area of the river or stream channel is reduced more than 3 percent.
	 71.9(2)  Urban areas. In urban areas:
	  a.   	 Stream bank protective devices along any river or stream draining more than 100 square miles.
	  b.   	 Stream bank protective devices along any river or stream draining between 2 and 100 square miles where the cross-sectional area of the river or stream channel is reduced more than 3 percent.