Big Pine Creek Ditch revisited: Planform recovery to channelization and the timescale of river meandering

Abstract

Channelization has changed the form and dynamics of rivers on a global scale. In the midwestern United States, widespread straightening of meandering headwater streams has been undertaken for the purpose of improving land drainage. Few studies have examined in detail how meandering streams respond to straightening, especially over timescales of nearly a century following straightening. This study uses historical aerial imagery and contemporary lidar data to examine how a small headwater stream that was straightened nearly a century ago, Big Pine Creek Ditch (BPCD) in Indiana, USA, has adjusted to straightening and to relate observed changes to stream power. The evolution of this fluvial system was examined in the late 1970s and this study updates that previous work using additional imagery and GIS-based methods, extending the timeline of analysis from 1932 to 2018. Results reveal that recovery varies spatially along the length of BPCD with some reaches not adjusting at all, some reaches increasing in sinuosity but then being artificially restraightened, and other reaches evolving continuously in response to channelization. For reaches that have evolved continuously, the rate of increase in sinuosity over time is directly related to bankfull stream power per unit length. Rates of increase in sinuosity per logarithmic unit of power per unit length have been linear and should attain the prechannelized relation between sinuosity and stream power over a timescale of about 100 years. Reaches with estimated bankfull stream power per unit area below 25 W m−2 exhibit no recovery of sinuosity, whereas those with power per unit area greater than 50 W m−2 have progressively increased in sinuosity. Between these thresholds, straightened reaches may or may not increase in sinuosity. Not all aspects of channel planform recovery are captured by changes in sinuosity; the prechannelized meandering stream exhibited greater lateral shifts in the position of the meander belt than do current meandering reaches. Overall, the study provides insight into spatial and temporal variability of recovery to channelization, the long-term recovery of meandering streams to straightening, as well as the timescale of meander development in straight channels.