GEOMORPHIC DIFFERENCES BETWEEN SIMILAR STREAMS WITH CONTRASTING ANTHROPOGENIC INFLUENCE IN THE KANSAS FLINT HILLS

A stream’s goal is to seek equilibrium with the surrounding land. Given an excess of sediment, the stream works to broaden its reach and deposit this extra material. If little sediment is added to a stream, a higher kinetic energy is available to scour the channel. Studying the reaction of streams to chronic disturbance facilitates understanding of how water quality can be maintained in streams.

The Kansas Flint Hills present a setting in which streams with chronic disturbance may be compared to streams with less historic anthropogenic influence. Anthropogenic influence in this investigation refers to direct disturbance in the form of stream crossings by track and wheeled vehicles as well as the disturbance of surrounding hill slopes from military maneuvers. To assess the impact of military maneuvers and of stream fording sites at Fort Riley Military Base, we are measuring the geomorphic characteristics of three reaches of second order ephemeral streams on Fort Riley and comparing them to streams having similar dependant variables. We are currently documenting stream morphologic parameters, such as sinuosity, entrenchment, aggradation, degradation, bed materials, bank stability, cross-sectional channel shape, and vegetation at all sites.

The constant influence of non-point-source pollution in Fort Riley streams increases the amount of sediment being transported from this area and threatens to smother the habitat of aquatic life. Stream reaches examined on Fort Riley are entrenched with steep banks, and inundated with silt-sized bed materials. Classified as F6 using the Rosgen scheme, the morphologies of these streams are easily disturbed by sediment loading.

The morphology of second-order stream reaches in drainage basins having similar bedrock, surficial sediments, vegetation, and slope near Fort Riley, but with considerably less human disturbance, are compared directly with the results from the Fort Riley streams. Typically these streams are less entrenched and channel bottoms are less muddy.