FLOOD06759

• County: Statewide
• Community: Rock Rapids, Iowa
• Basin: Statewide
• Title: Technical Assistance Report Rock River at Rock Rapids Iowa
• Date: 9/1/1995
• Prepared For: US Army Corps of Engineers
• Prepared By: Greenhorne & O'Mara, Inc.
• Floodplain - Doc Type: Project

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time, it does not appear that the levee would be suitable for requesting that the
property be removed from the floodplain from a regulatory standpoint.

The private ring levee would probably not have any significant impacts on the tOO-year
flood elevations on the Rock River. The location, height, size, and length of the levee
would not pose a severe impact in comparison to the overall width and location of the
floodplain. The structures and the levee are not located in the FEMA designated
floodway, but are located in the flood fringe. The existing flood boundaries of the Rock
River would not be adversely affected.

Oosure Structures
Closure structures are required at openings in levees when facilities such as roadways
and railroads pass through the levee at elevations below the level of protection
provided by the project. Within the Rock Rapids area there are two locations (site" A"
and site "B") where an existing or proposed levee have a roadway crossing that is
beIow the desired Ievel of protection, and that would require a closure structure. These
openings through the levees have moderate widths of about 40 feet.

There are several types of closure systems that could be used for openings in levees,
and general information for some of these systems is included in the following
paragraphs. In particular, this document will address stoplog structures, swing gates,
sand bags/ fill placement, and roadway ramps.

StopIog closure structures usually consist of one or more sets of horizontal aluminum or
steeI beams (or logs) which are stacked across an opening. For a relatively narrow
opening, one set of logs may span between vertical support slots instaIled at each edge
of the opening. Wider openings require a removable intermediate support post. The
stoplogs mayor may not have their own seals, but plastic sheeting, sand bags, or other
devices should be used to reduce leakage through the stoplogs. A storage area near the
location of the opening must be provided in order to store the stoplogs, removable
posts, and accessories. A typical detail for a stoplog closure structure is shown on plate
3. Advantages and disadvantages of stoplog closure structures are given beIow.

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