BIRDS POINT-NEW MADRID FLOODWAY

BACKGROUND

The Birds Point-New Madrid Floodway is a component of the Mississippi River and Tributaries (MR&T) Project, and is located on the west bank of the Mississippi River in southeast Missouri just below the confluence of the Ohio and Mississippi Rivers. The construction and operation of the floodway was authorized by the 1928 Flood Control Act and later modified by the 1965 Flood Control Act. The purpose of the floodway is to lower flood stages upstream and adjacent to the floodway during major flood events. The Floodway is some 35 miles in length and varies from 4 to 12 miles in width. It comprises about 205 square miles of alluvial valley land. The primary features of the floodway are the setback (mainline) levee, which extends from Birds Point, Missouri, to New Madrid, Missouri, and the frontline levee which is located on the west bank of the river and generally follows its alignment. Within the frontline levee, there are two fuseplug sections. These sections were designed and built 2 feet flower than the remaining portions of the frontline levee. The upper fuseplug section is 11 miles in length and is located in the northernmost reach of the frontline levee. The lower fuseplug is 5 miles in length and is located in the extreme lower end of the frontline levee. In addition, there is an existing 1500-foot gap which is located between the setback levee and the end of the frontline levee. This opening currently provides a drainage outlet for interior run-off and allows flood backwaters to enter the floodway.

EXISTING FLOODWAY OPERATIONAL PLAN

The existing Plan of Operation for the Floodway was reviewed by Missouri state officials in November 1985 and approved by the President, MRC, in January 1986. The plan required modification to the frontline levee that includes raising 12,500 feet of the upper fuseplug and 7,500 feet of the lower fuseplug and installing horizontal polyethylene pipe in three crevasse locations. These crevasse locations are designated as Inflow, Inflow/Outflow No. 1 and Inflow/Outflow No. 2. In addition to the modifications to the frontline levee, the Memphis District has acquired all materials, including the blasting agent that will be pumped into the pipes in the levee, and equipment necessary to place the floodway into operation.
In order to assure adequate water access to the crevasse sites, access lanes are required from the Mississippi River to and along the designated crevasses. With a project design flood rate of rise, approximately 2 feet per day, initial preparation of floodway is required when the stage at the Cairo, IL, gage is approximately 59 feet; completion of preparation of the Inflow Crevasse at 60 feet; and operation of the floodway begins upon order of the President, MRC.

PROJECT IMPACTS

General Considerations

The requirement to operate the floodway was examined with respect to each potential closure alignment considered in the Revised Supplemental Environmental Impact Statement. The types of issues analyzed or the impact of each alternative are as follows:

  Change of order for floodway operation will be needed for all alternatives

  Access lanes by barge need to be at least 9 foot (7.5 feet with clearance freeboard)

  Feasibility of land based operation was determined to not be feasible due to quantities involved and highway transport capacity

  Permanently loading and storing barges at Ensley Engineering Yard was considered

  Limited manpower and physical plant capability due to declining revetment mission, downsizing trend, and surplussing floating plant

  Timetable of Operations was considered, including commitments to locals & State to reduce start-up activities as well as attempts to simplify operations, reduce frequency of false starts, reduce costs

  Risks & Uncertainty with Larger Operation include the following:

   All alternatives increase risk for successful operation, but these have been minimized using approach of limiting crevasse length and crevasse location

   Constrain Crevasse Length to 5,500’

   Locate any Inflow/Outflow Crevasse on Frontline Levee

   Limit Operation to only one Inflow/Outflow Crevasse at bottom end of floodway 

Impacts and Changes due to the Recommended Plan

  Location of Inflow/Outflow Crevasse – No change

  Existing crevasse pipes – No change

  Time for loading – No change

  Blasting agent – No change

  Access Lanes – No change

  Need for Blue Hole / Sanding Lands – No change

  Authority – No change

  Real Estate Rights – No change