Providing Temporal Context to Channel Morphological Dynamics in Great Plains Intermittent Streams

Abstract

State and transition models (STMs) are used by landowners to make land management decisions by providing insight into the processes that govern degradation and recovery of ecosystems. Intensive monitoring and inclusion of long-term data is critical for an advanced understanding of riparian ecosystem dynamics and stream channel morphology. This study used repeated measures of stream channel morphology on intermittent streams in low gradient alluvial valleys to assess transitions for improved riparian STM development. Cross sectional and longitudinal surveys of channel morphology were conducted five to seven years apart. Each site was assigned a channel type and stability class so transitions between classifications could be compared. Analysis of multiple channel stability metrics and the multivariate trajectory of sites over time revealed general trends toward stability across the study area. Channels that were initially observed in a stabilizing state and channels that changed stability class had the greatest degree of change over time. This study supports the theory that destabilized channels will always seek an alternative stable state. Stabilizing channels are in a state of building resistance and resilience. Management of stabilizing channels should include practices that promote floodplain development through the establishment of riparian plant communities. This study provides context for the length of time that the stages of channel evolution take on intermittent streams in the Northern Great Plains. Managers are able to make well informed decisions when provided with a time frame for the changes a management practice is expected to support.