U.S. Geological Survey
Water-Resources Investigations Report 96-4243

Prepared in cooperation with the
KANSAS WATER OFFICE

Changes in High-Flow Frequency and Channel Geometry of the Neosho River Downstream From John Redmond Dam, Southeastern Kansas

By Seth E. Studley

CONTENTS

Abstract
Introduction
High-Flow Frequency
Channel Geometry
Summary
Referenced Cited

For additional information about the Fluvial Geomorphology Studies project, please visit: http://ks.water.usgs.gov/Kansas/fluvial/

FIGURES

Figure 1. Maps showing location of Neosho River Basin in Kansas and streamflow-gaging stations used for analysis in this study
2-5. Graphs showing:

Figure 2. 7-day and 30-day high-flow frequency curves for Neosho River at Strawn, Kansas, prior to completion of John Redmond Dam, and for Neosho River at Burlington, Kansas, after completion of John Redmond Dam
Figure 3. 7-day and 30-day high-flow frequency curves for Neosho River near Iola, Kansas
Figure 4. 7-day and 30-day high-flow frequency curves for Neosho River near Parsons, Kansas
Figure 5. Flow-duration curves for U.S. Geological Survey streamflow-gaging stations downstream from John Redmond Dam

Figure 6. Map showing National Weather Service climatic regions for Kansas
Figures 7-10. Graphs showing:

Figure 7. Total annual precipitation for climatic regions 6 and 9 in Kansas
Figure 8. Mean annual discharges at U.S. Geological Survey streamflow-gaging stations downstream from John Redmond Dam
Figure 9. Annual peak discharges for U.S. Geological Survey streamflow-gaging stations downstream from John Redmond Dam
Figure 10. Stages for mean annual discharges and median annual peak discharges at U.S. Geological Survey streamflow-gaging stations downstream from John Redmond Dam

TABLES

Table 1. U.S. Geological Survey streamflow-gaging stations used in this study
Table 2. Pre- and post-dam comparisons of high-flow frequency estimates for the Neosho River at Strawn and at Burlington, Kansas
Table 3. Pre- and post-dam comparisons of high-flow frequency estimates for the Neosho River near Iola, Kansas
Table 4. Pre- and post-dam comparisons of high-flow frequency estimates for the Neosho River near Parsons, Kansas
Table 5. Trend analysis of forcing variables tested in the Neosho River Basin downstream from John Redmond Dam
Table 6. Trend analysis of stages related to the mean annual discharge and median annual peak discharge at selected streamflow-gaging stations in the study area

CONVERSION FACTORS AND ABBREVIATIONS

Abstract

INTRODUCTION

The Neosho River in southeastern Kansas flooded 57 times in the 34-year period prior to 1964 (Department of the Army, Tulsa District Corps of Engineers, 1984), which resulted in numerous requests from the public to the U.S. Army Corps of Engineers for flood protection. The response to these requests was to build three flood-control dams in the Neosho River Basin ( fig. 1). The effect of one of the dams, John Redmond Dam (completed September 1964), on high-flow frequency and channel geometry of the Neosho River was the focus of a 1-year study (1995) conducted by the U.S. Geological Survery (USGS) in cooperation with the Kansas Water Office (KWO) and supported in part by the Kansas State Water Plan Fund. Results will contribute to improve understanding of the effects of dams on streams.

The purpose of this report is to describe changes in high-flow frequency and channel geometry of the Neosho River after the construction of John Redmond Dam. The scope of this report includes the analysis of high-flow frequency and stage-discharge relation changes at USGS streamflow-gaging stations downstream from John Redmond Dam and a comparison of the results of analyses based on data collected before and after completion of the dam.

The data used to determine high-flow frequencies and channel geometry were obtained from three currently operating USGS streamflow-gaging stations downstream from John Redmond Dam. In addition to these three stations, a discontinued station, which was located at Strawn, Kansas (07182400), was included to further analyze the high-flow frequency close to the dam. The discharge at the Strawn gage (operated from 1949 to 1963) should be comparable to what would have been recorded at the Burlington gage site if there would have been a gaging station at that site during that time period. The most current data was used whenever possible. The most current data are available for high-flow frequencies through the 1993 water year and for channel-geometry changes through the 1994 water year. Table 1 lists the four stations, their distance downstream from John Redmond Dam, drainage area, and period of record. The location of the streamflow-gaging stations is shown in figure 1.

A detailed description of the study area can be found in the Kansas Water Resource Board's Water Plan Study for the Neosho River Basin (Kansas Water Resources Board, 1961). The water plan study includes information on geology and soils as well as average annual precipitation and land use.

HIGH-FLOW FREQUENCY

High-flow frequency curves are used to estimate the exceedance probability of selected discharges. The median (50-percent exceedance-probability) discharge and the standard deviation of the fitted distribution curve help to describe the characteristics of the streamflow. In this study, comparisons of two curves, one using data prior to closure of John Redmond Dam and one using data after dam closure, are made using the discharge magnitudes of the 2-, 50-, and 95-percent exceedance probabilities as well as the standard deviation of each curve. Also, for this part of the report, the high-flow frequency curve for Strawn is illustrated and compared with data from the Burlington gaging station (map number 2, figure 1) because of their close proximity and because the streamflow-gaging station at Burlington was not installed until 1963.

The high-flow frequency curves developed for the Neosho River downstream from John Redmond Dam illustrate how the discharge characteristics have changed since the dam was completed in September 1964. High-flow frequencies for 7-day and 30-day high-flow discharges at the stations downstream from the dam for the period up to and including 1963 and the period 1965 through 1993 are shown in figures 2, 3, and 4. The differences for all stations are summarized in tables 2, 3, and 4. Since the closure of the dam, the discharge magnitudes associated with the upper end of the curves (lower exceedance probabilities) have been reduced, whereas those associated with the lower end of the curves (higher exceedance probabilities) have been increased. The magnitudes of the differences in the frequencies appear to be dependent upon the distance downstream from the dam. The differences are very large at Burlington, which is 5.3 mi downstream from the dam; they are much smaller at Parsons, which is about 140 mi downstream. This probably is due to a larger part of the drainage area being unregulated as the distance from the dam increases (approximately 27 mi² at Burlington and 1,863 mi² at Parsons). Also, the standard deviations of the logs of the 7-day and 30-day data are greatly reduced for the post-dam period. This is attributed to the regulation of releases through the dam.

Flow-duration curves for the periods before and after the construction of John Redmond Dam are shown in figure 5. For specific durations, the high-flow discharges have decreased subsequent to dam construction, and the medium- to low-flow discharges have increased. The discharges rarely, if ever, become as low as they did prior to completion of the dam because, although the primary purpose for the dam is flood control, it also is used to regulate low flow for the purpose of maintaining water quality in the Neosho River.

CHANNEL GEOMETRY

Results from the trend tests on the forcing variables are summarized in table 5. Forcing-variable data are graphically illustrated in figures 7, 8, and 9. No apparent trend was present in any of the variables tested. The tau values were below the critical value, and the p values were all larger than the alpha value, which indicates that there is no evidence to reject the null hypothesis. These results indicate no climatological change causing changes in the stage-discharge relations at the streamflow-gaging stations investigated in this report.

The results of the trend tests on the stage data are summarized in table 6, and plots of the stage data are presented in figure 10. There was little or no trend in the stages associated with the mean annual discharges at all three stations downstream from John Redmond Dam. This probably is because the preferred location for gaging stations is where there will be stable control for low to medium discharges, which means that there is little chance that the channel will scour or degrade at medium to low stages. The median annual peak-discharge stages did show trends at Burlington and Iola. There is a relatively large negative trend just downstream from the dam at Burlington (-0.104 ft/yr). Farther downstream at the Iola gaging station, the trend is not as large (-0.046 ft/yr), and at the Parsons gaging station, there was no evidence of a trend in the median annual peak stages.

Although these data indicate that some scouring is occurring at two of the streamflow-gaging stations, it is only a starting point in determining the amount of channel change in the Neosho River channel. A more definitive analysis of channel-geometry changes could be accomplished with surveys of channel cross sections.

SUMMARY

REFERENCES CITED