Channel Stability of the Neosho River Downstream from John Redmond Dam, Kansas —Kyle E

Prepared in cooperation with the KANSAS WATER OFFICE Channel Stability of the Neosho River Downstream From John Redmond Dam, Kansas —Kyle E. Juracek The stability of the Neosho River is not sufficient to conclude that John of property, general aesthetics, and channel downstream from John Redmond Dam has caused the Neosho recreation. The knowledge provided by Redmond Dam, in southeast Kansas, River channel to change more than it this study will provide some of the was investigated using multi-date otherwise would have changed without information needed to best manage the aerial photographs and stream-gage the dam. Neosho River system. information. Bankfull channel width To determine the effect of John was used as the primary indicator Redmond Dam, a study of the Neosho Description of Study Area variable to assess pre- and post-dam River that compares the channel before, channel change. Five 6-mile river during, and after completion of the dam The focus of this study was the reaches and four stream gages were was undertaken by the USGS in coop middle 180-mile reach of the Neosho used in the analysis. Results indicated eration with the Kansas Water Office. River between John Redmond Dam and that the overall channel response to the The objective of this study was to the Kansas-Oklahoma State line altered streamflow regime and sediment determine whether or not the Neosho (fig. 1). Throughout this reach the load introduced by the dam has been River channel has widened in response Neosho River is characterized by a minor. Aside from some localized to the changes in flow regime and meandering, gravel-bed channel. The channel widening, there was little post- sediment load introduced by the dam. channel slope averages about 1.2 feet dam change in bankfull channel width. Pre- and post-dam channel stability was per mile. Riverbank height varies from The lack of a pronounced post-dam assessed using multi-date aerial about 15 to 30 feet. The channel bed channel response may be attributable photographs and streamgage infor frequently is situated on bedrock. to a substantial reduction in the mation. Alluvium in the Neosho River Valley magnitude of the post-dam annual peak Important issues related to the averages about 25 feet in thickness and flows in combination with the stability of the Neosho River channel is typified by silt with a basal layer of resistance to erosion of the bed and include protection of riparian resources, sand and gravel that averages about bank materials. Also, the channel may protection of habitat for threatened and 3 feet in thickness. The channel-bank have been overwidened by a series of endangered species (for example, the materials consist mostly of cohesive silt large floods that predated construction Neosho Madtom, Noturus placidus), and clay and are relatively resistant to of the dam. and bank stabilization as related to loss erosion compared to sand banks. Also, Introduction The construction and operation of a reservoir can have a substantial effect on the stability of the river channel downstream from the dam. Since its completion in 1964, the downstream effect of John Redmond Dam on the Neosho River in southeast Kansas (fig. 1) has been much debated. Previous studies by the U.S. Army Corps of Engineers (COE) (1972) and the U.S. Geological Survey (USGS) (Studley, 1996) have indicated the possibility of channel widening. Also, anecdotal evidence of perceived channel widening has been provided by residents living along the Neosho River as far as 165 mi downstream from the dam. The available evidence, however, John Redmond Dam on the Neosho River near Burlington, southeast Kansas. U.S. Department of the Interior USGS Fact Sheet FS–088-–99 U.S. Geological Survey April 1999 John Redmond EXPLANATION Reservoir 1 John Redmond 4 Current U.S. Geological Survey Dam streamflow-gaging station—Number 95°30' Burlington 2 is map number used in table 1 Le Roy N Iola reach 1 eo Discontinued U.S. Geological Survey sh 38° o streamflow-gaging station—Number is map number used in table 1 3 Iola Le Roy reach Humboldt reach Overflow dam Humboldt 95° Boundary of Chanute Neosho River Basin R iv er Erie Neosho Erie reach River Study KANSAS area MISSOURI 4 Ar ka Parsons n Neosho River s a Basin s KANSAS Oswego reach MISSOURI Oswego OKLAHOMA ARKANSAS River Chetopa KANSAS 37° Base from U.S. Geological Survey digital data, 1:100,000, 1995 OKLAHOMA Universal Transverse Mercator projection 0 10 20 30 MILES Zone 14 & 13 Converted to Lambert Conformal Conic projection, 0 10 20 30 KILOMETERS Index map Standard parallels 33° and 45°, central meridian -98°15' Figure 1. Location of Neosho River Basin, study area, river reaches, and streamflow-gaging stations. the channel banks are typically covered used as the primary indicator variable indicators used in the delineation of the by partial to complete mature tree cover to assess channel change after the com bankfull channel included breaks in which may enhance bank stability at pletion of the dam. slope, the tops of point bars, and some locations. Five 6-mile river reaches were changes in vegetation. The channel Several tributaries contribute unreg selected for use in this study (fig. 1) centerline was added, and all ulated flow to the Neosho River down- with the objective being to obtain a information was digitized. Mean stream from John Redmond Dam. Also spatially representative sample while bankfull channel width then was noteworthy are 12 overflow dams avoiding, to the extent possible, estimated for all reaches and dates as (fig. 1) that were constructed within the localized human-caused or natural channel area divided by channel main-stem channel mostly in the 1930's conditions that might obscure channel centerline length. or 1950's. Changes in the streamflow adjustment. Human-caused conditions To compare pre- and post-dam regime attributable to the operation of include overflow dams (fig. 1), bridges, channel stability, the mean bankfull John Redmond Dam have included a and channel modifications (for channel widths for all reaches and dates decrease in the magnitudes of peak dis example, riprap). Natural conditions were tabulated, and pre- and post-dam charges (flows) and an increase in the include split-channel locations and hard differences were evaluated. For each magnitudes of low discharges (fig. 2) points (that is, locations where the reach, pre-dam change was computed (Studley, 1996). Post-dam suspended- channel is situated along the valley as the percentage difference in mean sediment concentrations are substant wall). Additional factors considered in bankfull channel width between the ially reduced immediately downstream the selection of the reaches included pre-dam and construction time periods. from the dam. proximity to John Redmond Dam and Similarly, post-dam change was the availability and usability of aerial computed for each reach as the Methods photographs. percentage difference in mean bankfull For each reach, aerial photographs channel width between the construction A stable river channel naturally were obtained for three time peri and post-dam time periods. The magni meanders across its river valley over ods—pre-dam (late 1930's), construct- tude and direction of the changes were time while maintaining approximately ion (early 1960's), and post-dam (early used to assess pre- and post-dam the same cross-sectional shape. There- 1990's). The bankfull channel area was channel stability for the individual fore, changes in channel geometry may interpreted from the aerial photographs reaches as well as the entire system. be used to infer channel instability. In for each time period and traced on a Due to various potential sources of this study, bankfull channel width was scale-stable mylar overlay. Primary error in the use of aerial photographs to measure bankfull channel widths, only a change in bankfull width of 10 per- Downstream Effects of Dams result in channel narrowing as vegetation cent or more was considered signifi on River Channels encroaches. An exception is the case where the channel bed is armored or cant. situated on bedrock. Unable to effect Information from USGS Primary changes introduced by a ively scour the resistent channel bed, the streamflow-gaging stations (fig. 1, table dam include a reduction in the river's river may instead erode laterally and thus 1) was also analyzed to assess pre- and sediment load as well as an alteration of widen its channel. Typically, channel post-dam channel stability downstream the flow regime. Typical changes in the degradation initiates near the dam flow regime include a reduction in the from the dam. A comparison of pre- following closure and eventually may magnitude of peak flows and a possible migrate a considerable distance and post-dam conditions included an increase in the magnitude of low flows. downstream (Williams and Wolman, assessment of stage-discharge, dis Such artificially introduced changes 1984). charge-width, discharge-area, and may trigger an adjustment by the river The type, rate, duration, and discharge-velocity relations. The as it attempts to re-establish an approxi downstream extent of channel degrad Parsons gaging station was excluded mate equilibrium between the channel ation downstream from dams are and the discharge and sediment load controlled by a number of factors, from all analyses due to back-water being transported. including discharge, sediment load, bed effects from an overflow dam located In general, rivers downstream from and bank material composition, local 2.7 miles downstream from the gage dams initially adjust by channel bed-elevation control (for example, (fig. 1, map number 4). The gaging degradation. Typically, a river will bedrock, armoring), channel geometry, stations provide site-specific inform scour, and thus lower, its channel bed as climate, tributary inflow, and vegetation.

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