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Kansas Water Science Center

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

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

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

Multiply By To obtain
cubic foot per second (ft³/s)       0.02832 cubic meter per second
foot (ft)     0.3048 meter
foot per year (ft/yr)     0.3048 meter per year
inch (in.) 2.54 millimeter
mile (mi)   1.609 kilometer
square mile (mi²)   2.590 square kilometer

Water year: A water year is a 12-month period, from October 1 through
September 30, designated by the calendar year in which it ends. Years
are water years in this report unless otherwise stated.

Abstract

The streamflow regimen of the Neosho River downstream from John Redmond Dam in southeastern Kansas has changed significantly since the dam's completion in 1964. The controlled releases from the dam have decreased the magnitudes of peak discharges and increased the magnitudes of low discharges. The trends in river stage for selected discharges also have changed at two of the streamflow-gaging stations--those closest to the dam. There is a significant downward trend in the stages associated with the median annual peak discharges, but no significant trend in the stages associated with the annual mean discharges, which indicates that the river channel is increasing in width but not depth or that the flow velocity has increased at the streamflow-gaging stations. Because there were no significant trends present in precipitation, mean annual discharge, or annual peak discharge, the changes are attributed to John Redmond Dam.

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.

Table 1. U.S. Geological Survey (USGS) streamflow-gaging stations used in this study.
[mi, miles; mi², square miles; --, not applicable]

Map
number
( fig. 1)
USGS
station
number
USGS station name Distance
downstream from
John Redmond
Dam (mi)
Drainage
area (mi²)
Period of record
(water years)
1 07182400 Neosho River at Strawn, KS      -- 3,015 1949-63
2 07182510 Neosho River at Burlington, KS      5.3 3,042 1963-93
3 07183000 Neosho River near Iola, KS   56.3 3,818 1918-93
4 07183500 Neosho River near Parsons, KS 139.6 4,905 1922-93

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.

Table 2. Pre- and post-dam ccomparisons of high-flow frequency estimates for the Neosho River
at Strawn (07182400) and at Burlington, Kansas (07182510)

Discharge, in cubic feet per second
7-day high flow 30-day high flow
Exceedance
probability
(percent)
Pre-dam
(Strawn)
Post-dam
(Burlington)
Percentage
differences
Pre-dam
(Strawn)
Post-dam
(Burlington)
Percentage
differences
  2.0 102,377 13,501 -87 37,491 13,266   -65
50.0     8,306 10,813 +30   3,768   7,005   +86
95.0     1,099   4,266 +288        321   2,064 +540
Standard
deviation of
logs
                    .533                     .173   -68                     .580                     .249   -57

Table 3. Pre- and post-dam ccomparisons of high-flow frequency estimates for the Neosho River
near Iola, Kansas (07183000)

Discharge, in cubic feet per second
7-day high flow 30-day high flow
Exceedance
probability
(percent)
Pre-dam Post-dam Percentage
differences
Pre-dam Post-dam Percentage
differences
  2.0 86,400 18,700 -78 37,800 14,700   -61
50.0 11,800 13,000 +10   5,130   9,070   +77
95.0     1,890   5,290 +180       746   2,890 +287
Standard
deviation of
logs
                    .456                     .176   -61                     .472                     .225   -52

Table 4. Pre- and post-dam ccomparisons of high-flow frequency estimates for the Neosho River
near Parsons, Kansas (07183500)

Discharge, in cubic feet per second
7-day high flow 30-day high flow
Exceedance
probability
(percent)
Pre-dam Post-dam Percentage
differences
Pre-dam Post-dam Percentage
differences
  2.0 82,441 47,531  -42 45,182 22,598   -50
50.0 19,201 20,635    +7   8,926   12,684   +42
95.0     3,351   6,988 +108   1,329     3,590 +170
Standard
deviation of
logs
                    .397                    .241   -39                     .436                     .251    -42

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

Reservoir release operations are known to produce channel changes downstream from a dam (Williams and Wolman, 1984). Other variables such as precipitation and streamflow also can cause changes in the river channel. These variables, known as driving or forcing variables, were tested for trend along with the response variable, stage. Changes with time in the stage-discharge relation can be used to infer channel changes in the immediate vicinity of the streamflow-gaging station (Wahl and Weiss, 1995). These variables were analyzed for the period up to the end of the 1963 water year and also for the period from 1965 through 1993, which coincide with the periods before and after completion of John Redmond Dam. The forcing variables considered in this study are described below:

    Precipitation data are the annual averages and were obtained from the National Weather Service for Kansas climatic regions 6 and 9. These two regions cover most of the Neosho River Basin in southeast Kansas. The results of the trend test would indicate whether or not a climatic change occurred in the study area during the period of interest.

    Annual mean discharge is the yearly average of the daily mean discharges for each station. The trend-test results are expected to show any systematic departures from normal discharges, which could cause channel changes.

    Annual peak discharge is the maximum instantaneous discharge for a given year. Changes in the magnitude of annual peaks can have an effect on the geometry and stability of the channel

    These forcing variables, except for precipitation, were only tested to determine if there are other systematic factors, in addition to the regulation effect of the dam, that may be affecting the response of the system. Precipitation was tested to determine any climatic trends.

The response variable tested for trend is the stream stage at selected discharge magnitudes. Two discharge magnitudes were selected. The annual mean discharge, or the average discharge for the period of record, was used because generally it reflects moderate to low discharges. The median annual peak discharge was used because it generally is about the same magnitude as the 2-year flood recurrence interval and because it generally reflects high to moderate discharges.

The stage-discharge relation tables throughout the period of record for each station were used to determine the stream stage (height of water surface above a datum) of each of the selected discharges. The time variable associated with each stage is the year, month, and day in which the stage-discharge relation was put into effect; therefore, there is not a separate stage associated with each year but only a stage associated with each stage-discharge relation.

The test used to determine the presence of trends commonly is referred to as Kendall's tau trend test (Kendall, 1938; 1975). It is a nonparametric test that, in application, tests the null hypothesis that the data are random observations that are identically distributed and not time dependent; no assumption is made about the identity or form of the underlying distribution.

Under the null hypothesis, tau values significantly different from zero are not expected, and their occurrence casts doubt on the truth of the null hypothesis. The test consists of comparing the observed value of tau for the sample with a critical value from the theoretical distribution for tau. If the absolute value of tau for the sample is greater than the critical value, the null hypothesis is rejected; that is, the observed value of tau is too great to have been obtained plausibly by random sampling from a single distribution without time trends. If the observed absolute value of tau does not exceed the critcal value, the sample does not provide a basis for rejecting the null hypothesis.

The probability that tau will exceed the critical value when the null hypothesis is true is called the significance level (alpha) of the test; thus, the significance level is the probability of erroneously rejecting a true null hypothesis. High significance is associated with small values of alpha. In this study, an alpha value of 0.01 was used, representing a 1-percent probability of erroneously rejecting the null hypothesis. The attained significance level for a particular test, or p value, indicates the strength of the test result when compared with the alpha value.

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.

Table 5. Trend analysis of forcing variables tested in the Neosho River Basin downstream from John Redmond Dam
[precipitation data from the National Weather Service]

Variable tested Period
years in test
Number of
(water years)
tau p value
Annual precipitation
Climatic region 6, east-central Kansas 1895-1994 100 +0.04 0.51
Climatic region 9, southeast Kansas 1895-1994 100 +.11 .10
Annual mean discharge
at Burlington, Kansas (07182510)
     Post-dam
1965-93 28 -.08 .55
near Iola, Kansas (07183000)
     Pre-dam
     Post-dam
1918-64
1965-93
54
29
+.07
+.05
.42
.68
near Parsons, Kansas (07183500)
     Pre-dam
     Post-dam
1922-64
1965-93
43
29
 0
  +.11
.99
.39
Annual peak discharge
at Burlington, Kansas (07182510)
     Post-dam
1965-93 29 -.05 .68
near Iola, Kansas (07183000)
     Pre-dam
     Post-dam
1918-64
1965-93
58
29
-.10
+.18
.27
.16
near Parsons, Kansas (07183500)
     Pre-dam
     Post-dam
1922-64
1965-93
43
28
    -.01
   +.24
.92
.07

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.

Because the stages are declining at the higher discharges and not at the lower discharges, it can be assumed that the channel is either widening rather than deepening or the flow velocity has increased. Also, the results of the trend tests show that there is a decrease in the magnitudes of the trends as the distance downstream from the dam increases and less proportion of the drainage area is regulated by the dam.

Factors that could be affecting the scouring of the upper part of the channel cross section are the procedures used for reservoir releases, increased construction of levees downstream from the dam, channelization of sections of the river, and changes in land use along the flood plain. All of these factors can change the average velocity of the streamflow and (or) change the duration of higher streamflows, which generally will change the amount of scour or deposition.

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

A description of the effects of John Redmond Dam on the high-flow frequency and channel geometry of the Neosho River downstream from the dam is presented in this report. Long-term data from four U.S. Geological Survey streamflow-gaging stations were used to calculate 7-day and 30-day high-flow frequencies and to determine the river stages for the annual mean discharges and the median annual peak discharges for each streamflow-gaging station for the periods before and after completion of the dam.

High-flow frequency and flow-duration results show that there has been a change in high-flow frequencies since completion of John Redmond Dam. Discharge magnitudes during periods of low flow have increased, and both the magnitude and frequency of high flows have decreased.

A Kendall's tau test for trend was applied to the forcing variables (precipitation, annual mean streamflow, and annual peak discharge) at each of the streamflow-gaging stations. These forcing variables, except for precipitation, were only tested to determine if there were trends within the pre- and post-dam periods. Precipitation was tested to determine any climatic trends. The results of the trend test indicate that there is no significant trend in the data and, therefore, there is no evidence of climatic effects on the changes found in the high-flow frequencies. Kendall's tau trend test also was used to test for trends in the river stages for the annual mean discharges and the median annual peak discharges at each of the streamflow-gaging stations. The results of the test indicate that there is a downward trend at the two streamflow-gaging stations closest to the dam and that the magnitudes of the trends decrease as the distance downstream from the dam increases.

REFERENCES CITED

Department of the Army, Tulsa District Corps of Engineers, 1984, John Redmond Dam and Reservoir, Kansas: U.S. Government Printing Office, pamphlet.

Kansas Water Resources Board, 1961, State water plan studies, Part A. Preliminary appraisal of Kansas water problems, Section 7, Neosho Unit: Topeka, Kansas, 135 p.

Kendall, M.G., 1938, A new measure of rank correlation: Biometrika, v. 30, p. 81-93.

____1975, Rank correlation methods: Charles Griffin, London.

Wahl, K.L., and Wahl, T.L., 1988, Effects of regional ground-water level declines on streamflow in the Oklahoma Panhandle: American Water Resources Association Proceeding of Symposium on Water-Use Data for Water Resources Management, August 1988, Tucson, Arizona, p. 239-249.

Wahl, K.L., and Weiss, L.S., 1995, Channel degradation in southeastern Nebraska rivers: American Society of Civil Engineers Proceedings of Symposium on Watershed Management, First International Conference on Water Resources Engineering, August 14-16, 1995, San Antonio, Texas, p. 255.

Williams, G.P., and Wolman, M.G., 1984, Downstream effects of dams on alluvial rivers: U.S. Geological Survey Professional Paper 1286, 83 p.

For additional information contact:

Kyle Juracek
U.S. Geological Survey
4821 Quail Crest Place
Lawrence, KS 66049-3839
Telephone: (785) 832-3527
Fax: (785) 832-3500
Email:
kjuracek@usgs.gov