Monitoring and Modeling the Effect of Agricultural Drainage and Recent Channel Incision on Adjacent Groundwater-Dependent Ecosystems

Channel incision isolates flood plains, disrupts sediment transport, and degrades riparian ecology. Reactivation and periodicity of incision may affect the water table and hydrological conditions far beyond the stream margin. Long-term incision and its recent acceleration along Iron Springs Creek, North Dakota, USA, has affected adjacent ecosystems. An agricultural surface drain empties directly into the original spring-fed source of the creek, which triggered channel erosion both up- and downstream. Historical maps, recent LiDAR, and field surveying were used to characterize incision since ditch excavation in 1911. Although the soils are sandy, small hydrological gradients impede natural drainage in the surrounding stabilized dunes. Incision resulting from expanded drainage and increased precipitation has been as much as 5 m. Numerical models of lateral groundwater profiles corroborated with field measurements show that the nearby water table responds quickly, becoming deeper and less variable. With 1 m of recent incision, model evapotranspiration rates are decreased 50% to 15% from the channel margin to 1 km, respectively, and the hydropattern disrupted >1 km. Species diversity is reduced and floristic quality is 25% less near the drain. A near-channel solution to erosion—fencing out cattle—failed to mitigate the problem because a broader watershed approach was necessary.

R. S. Sigafoos’s 1961 and 1964 papers on botanical evidence of paleofloods

The interaction between vegetation and fluvial processes leaves many possibilities for research. Since the publication in the early 1960s of the US Geological Survey Professional Papers by R.S. Sigafoos, numerous contributions in paleohydrology and riparian ecology have deepened the interaction between vegetation and fluvial geomorphology. In this article, we briefly review the impact of Sigafoos’ research in past and current scientific developments. We highlight the importance of the botanical evidence described by Sigafoos and the need for further work in this research line.