Final Feasibility Report
Report Enclosures
Report Maps
Environmental Assessment and FONSI
Economics Appendix
Engineering Appendix
Real Estate Appendix
Cost Estimating Appendix
Public Involvement Appendix

Manhattan Kansas Levee Review Plan (pdf)

The Flood Control Act approved 3 September 1954 (Title II, Public Law 780, 83d Cong., 2d Sess., H.R. 9859) authorized the
original Manhattan, Kansas, local flood protection project (also known as the “Manhattan Kansas Levee”).  Construction of the project began on 4 May 1961, and local interests accepted the completed project for operation and maintenance in July 1963.

Section 216 of the 1970 Flood Control Act authorizes the Corps of Engineers to review previously completed Civil Works projects.  This Section 216 feasibility study is conducted in accordance with the guidance and procedures contained in Engineer Regulations ER 1105-2-100 (The Planning Guidance Notebook, April 2000) and ER 1165-2-119 (Modifications to Completed Projects, September 1982).

Section 216 authority reads as follows:

The Secretary of the Army, acting through the Chief of Engineers, is authorized to review the operation of projects, the construction of which has been completed and which were constructed by the Corps of Engineers in the interest of navigation, flood control, water supply, and related purposes, when found advisable due to the significantly changed physical or economic conditions, and to report thereon to Congress with recommendations on the advisability of modifying structures or their operation, and for improving the quality of the environment in the overall public interest.

Manhattan, Kansas Levee Unit Map

The purpose of the existing Manhattan Kansas local flood protection project is flood risk management for the Manhattan area.  The city lies along the Kansas River with major tributaries that connect within the immediate vicinity.  The Big Blue River is on the east side of the downtown area and connects to the Kansas River on the southeast.  The Corps of Engineers Tuttle Creek Lake is situated just to the north of Manhattan with the Big Blue River flowing into and out of Tuttle Creek Lake.  Tuttle Creek is a major lake in the Kansas River basin system of lakes, which are critical to the Corps’ flood risk management mission for both the Kansas and Missouri Rivers.  Wildcat Creek is situated within the western area of the city and also flows into the Kansas River.  The local confluence of so many rivers and tributaries makes public awareness of flooding hazards an important issue in Manhattan. 

 

The urban Manhattan floodplain includes a centrally located downtown and commercial area, a major regional shopping mall, hotels and associated retail centers.  Residential neighborhoods are generally situated to the west and north of the downtown area, and a light industrial area comprises the eastern half of the study area. 

 

This study was triggered by an incident in July of 1993.  With approximately 60,000 cfs released from Tuttle Creek Lake flowing in the Big Blue River past Manhattan, and approximately 100,000 cfs flowing in the Kansas River, some problems related to potential overtopping were indicated along the Big Blue River section of the Manhattan levee.  The design documentation for the Manhattan levee describes a system designed for a significantly higher coincident flow regime than was experienced in 1993. 

 

During the last two decades, the City of Manhattan has undertaken a beneficial series of short-term actions including engineering studies and levee improvements to better address the potential overtopping threat posed under events similar to the 1993 flood. Moreover, in light of the strong population growth in Manhattan and the close proximity to sources of potential major flooding, this feasibility study aims to analyze significant reliability improvements for a variety of large flood events and determine an appropriate course of action suited for the next 50 years.    

The Manhattan levee is located west and north of the confluence of the Big Blue River and the Kansas River in Manhattan, Kansas. The levee consists of protection along Wildcat Creek, the Kansas River, and the Big Blue River.  The levee embankment begins at Station 8+50 and ends at Station 272+85. The levee starts north of Wildcat Creek and is roughly aligned with 15th Street in Manhattan, Kansas. The levee follows the alignment of Wildcat Creek from Station 8+50 to Station 35+00, where it begins to parallel Pottawatomie Avenue to station 60+00.  The levee alignment then turns to the northeast and turns north at 80+00 to align with the Kansas River. The alignment with the Kansas River continues to the confluence with the Big Blue River at approximately Station 173+00. From the confluence, the levee turns towards the northwest, aligning with the Big Blue River until Station 209+00, where it turns further to the west and splits off from the Big Blue River. The levee continues in a west-northwest direction and aligns parallel to an existing drainage channel to its end at Station 272+85.

 

The Manhattan levee is approximately 28,850 feet long.  The levee was typically constructed with a 10-foot crown width and three horizontal to one vertical (3H: 1V) embankment slopes. The embankment is a zoned embankment.  The landside portion consists of a large “random fill” section.  The random fill was obtained from nearby channel improvement excavations and other local borrow areas. The random fill ranges from silty sands to lean clays. The riverside section is a minimum 2-foot-thick “impervious fill” section that is assumed to consist of locally available low-permeability lean and/or fat clays.  Underseepage control was provided where needed by underseepage berms and relief wells.  Stability berms were placed in the following reaches: 1) between Station 77+00 and 81+25, 2)  between Station 112+50 to 140+00, 3) between Station 160+50 and 179+00, 4) between Station 194+20 and 269+80, and 5) between Station 269+80 and 272+00. Six relief wells were originally installed at the Poyntz Avenue pump station inlet ditch. 

The City of Manhattan, Kansas owns and operates the Manhattan, Kansas levee unit and is the local sponsor for this feasibility study. The City serves as the primary local point of contact for all community-related matters regarding this study. City staff work with the Corps of Engineers study team members on a routine basis and ensure that City and local considerations are taken into account as the study progresses. 

The feasibility analysis and decision-making process draws upon the information developed during earlier studies, and uses existing and readily available information whenever such information is deemed adequate and appropriate for the necessary quality expectations of the final feasibility product.

The feasibility study has undertaken extensive new hydrological and hydraulic modeling of the area around Manhattan and specifically the Big Blue River and Kansas River confluence. Additionally, comprehensive existing condition geotechnical and structural studies were conducted. When taken together, these technical analyses paint a picture of the existing project reliability and safety, and the risks associated with the existing levee unit. The results of the technical analysis helped guide the study into the development and evaluation of appropriate potential reliability improvements. Potential flood risk management improvements were packaged into a set (or array) of early project alternatives which underwent further screening and evaluation.

The study team assembled existing condition information to determine potential economic damages from various types of levee performance concerns and evaluated the potential benefits associated with an early preliminary array of project alternatives. The team conducted public involvement activities in conjunction with the City of Manhattan, and performed the overall plan formulation and evaluation actions necessary to document a recommended course of action.

A Draft Feasibility Report and Environmental Assessment was published in June 2014 containing recommendations for improvements to the existing levee unit to reduce flood risk and improve levee reliability. The Draft Feasibility Report was made available on this site for a 30-day public review and comment period.  Comments received, with responses, are documented within the Final Feasibility Report.

The Final Feasibility Report was prepared by the project team in August 2014 and was approved by the Corps of Engineers’ Civil Works Review Board on November 20, 2014.  The associated Chief’s Report is currently under review by various Federal agencies and the State of Kansas prior to a final decision by the Chief of Engineers regarding transmission of the Report to Congress for authorization.

 

 

 

NEPA is the acronym for the National Environmental Policy Act of 1969, as amended. (42 U.S.C. §§4321-4347). NEPA requires Federal agencies, like the Corps, to consider the environmental consequences of an action along with economics and technical factors during project planning and prior to decision-making. In addition, NEPA requires Federal agencies to take measures that protect, restore, and enhance the quality of the human environment, i.e. the natural and physical environment and the relationship of people with that environment.

The NEPA process provides the decision-maker with a comparison of environmental impacts resulting from alternative actions. Some important NEPA concepts are:

· Public participation and input
· Systematic, interdisciplinary study approach (biologists, economists, archaeologists, engineers, and many other disciplines contributed to the study)
· Full disclosure of the findings from the planning process

Documents prepared for Public and Agency review in this study include:

· Feasibility Study Report - Both a Draft Feasibility Report and a Final Feasibility Report.

· Environmental Assessment (EA) and Finding of No Significant Impact (FONSI)

Public participation was solicited through a 2013 public meeting in the Manhattan area and a 30-day comment period on the Draft Report and EA in 2014.

In order to encourage public participation in the NEPA process and ensure full public disclosure, the Corps will utilize this website to provide information to the public on the study process and recommendations. In addition, the Corps will also provide news releases on important project milestones, meeting announcements, and comment deadlines to media sources in the project area.

 

 

The Endangered Species Act of 1973, as amended, is a Federal Law that was enacted to protect endangered and threatened species and their habitat.

The Corps, as a Federal agency, is required by Section 7 of the Endangered Species Act (16 USC 1536) to use our existing authorities to conserve federally listed threatened and endangered species and, in consultation with the U.S. Fish and Wildlife Service, to ensure that our actions do not jeopardize listed species or destroy or adversely modify critical habitat.

Three federally listed threatened or endangered species are known to occur in Riley and Pottawatomie Counties. These include: the federally listed endangered interior least tern (Sterna antillarum); the federally listed threatened piping plover (Charadrius melodus); and the federally listed endangered Topeka shiner (Notropis Topeka). The U.S. Fish and Wildlife Service has NOT identified any critical habitat for these listed species within or near the Manhattan Kansas local flood protection project area.

Least Tern   
Piping Plover

Major floods on the Kansas River are usually caused by a series of short-duration, high-intensity storms following a protracted period of general rains which reduce the infiltration capacity of the soil to a minimum and cause a greater than normal flow in the stream channels. Many of the early floods in the Kansas River Basin are a matter of legend and tradition rather than actual historical record. Early floods affecting the area in the vicinity of Manhattan occurred in 1785, 1826, 1844, 1845, 1851, 1858, 1870, 1881, and 1886, but very little is known concerning these floods (USACE 1959). More recent flood events for which records are available occurred in 1903, 1904, 1908, 1915, 1935, 1941, 1945, 1947, 1948, 1950, 1951, and 1993. The 1844 flood appears to have produced the maximum stages of record on the Kansas River followed in magnitude by the 1951, 1903, and 1993 stages.

 

Flood of 1844

A great flood is known to have occurred on the Kansas River in June 1844. Data are not available on the nature, extent, and magnitude of the storm rainfall, and only fragmentary data on flood stages are available. A stage of about 40 feet occurred on the Kansas River at Manhattan.

Flood of 1903

The second largest flood for which reliable stage records are available occurred during the latter part of May and the first part of June 1903. This flood resulted from extraordinarily heavy rainfall the last five days in May preceded by above-normal rainfall throughout May. The rainfall at Abilene was estimated at 15 inches on May 28. Flood stage was exceeded approximately 16 days at Manhattan.

Flood of 1951

The maximum flood of record occurred in July 1951 and resulted from the combined effects of well above average rainfall in May and June 1951 and a major event spanning four days (July 9 through 12) of extremely heavy precipitation over the lower portion of the Kansas River Basin. About 40 percent of Kansas received more than 10 inches of rain during June 1951. This area included most of the Smokey Hill River Basin and portions of the Republican River Basin. The Big Blue River basin north to the Nebraska border had rainfall in excess of 12 inches, with one area exceeding 14 inches.

The Kansas River at Manhattan was above flood stage (17 feet) on June 4, June 7 through 19, and June 22 through July 24, 1951 for a total of 47 days. The maximum gage height of 33.40 feet occurred at 3:00 a.m., July 13, with an estimated discharge of 300,000 cfs in the Kansas River and about 98,000 cfs in the Big Blue River.  The USACE reported peak discharge for the Big Blue River near Manhattan in the 1959 report varies approximately 4600 cfs from the USGS peak discharge of 93,400 cfs recorded for the Big Blue River near Manhattan Gage in the 1951 flood.

Flood of 1993

The third largest flood for which reliable stage records are available occurred in July 1993. Moderate to major flooding occurred on the Kansas, Big Blue, Black Vermillion, Smoky Hill, Solomon, Saline, and Republican Rivers and their tributaries. As with the flood of 1951, heavy rainstorms in July were preceded by several months of above average rainfall. Manhattan received more than 100 percent of the normal precipitation (1961 to 1990 average) for January through June 1993. May through July precipitation at Manhattan was 35.38 inches and was the second wettest period in 104 years of record. July rainfall was 535 percent of the normal.

 

 A comparison of observed controlled and simulated uncontrolled daily mean discharge in the Blue River near Manhattan for July 1993 indicated that the storage of floodwaters in Tuttle Creek Lake reduced a potentially devastating flood of more than 95,000 cfs on July 5 on the Big Blue River near Manhattan to a much less destructive flood of 60,000 cfs on July 25. The water surface elevation in the Big Blue came within 3 to 4 feet of the top of the Big Blue River section of the Manhattan Kansas levee.  Without the reservoir storage, the Big Blue River near Manhattan would have overtopped the Federal levee, and flooding downstream along the Kansas River would have been much more severe. High stages on the Big Bluer River were most noticeable upstream and near the U.S. Hwy 24 and Union Pacific bridge crossings. The Manhattan levee did not fail, but this incident prompted great concern about the levee under potential higher flow conditions.

 

 

Flood of July 1951:

 

Aerial view southwest, showing inundation of the south portion on the City of Manhattan, Kansas during the flood of July 1951.  The Griffith Stadium is shown at right center of photograph.  Construction of levees, floodwalls, pumping plants and river channel improvements at Manhattan, and upstream reservoir control, is proposed to prevent floods of this type.

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Flood of 1993:

Kansas River view from Highway 177 into downtown during 1993 flood.  Note that the Kansas River was not very high on this portion of the Manhattan Kansas levee and was only flowing 100,000 cfs, which is significant but not a major flood condition.

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Dix Subdivision:

The Dix Subdivision in northern part of Manhattan, Kansas.  This area is outside the Manhattan Kansas levee and was flooded due to backwater from the Big Blue River. The levee is just out of view in the foreground. The levee held in 1993 and the interior of the levee remained relatively dry.

The U.S. Army Corps of Engineers and the City of Manhattan hosted a public workshop on April 17, 2013, in Manhattan, Kan., from 5:30 to 7:30 p.m. at the Manhattan Fire Department. The meeting offered the general public, agencies and stakeholders an opportunity to see and hear information about the existing Manhattan Levee and genesis of the levee improvements feasibility study. The meeting also provided a good early opportunity to comment on concepts for long-term levee reliability improvements.