EXPLAINING POSSIBLE GEOMORPHIC IMPLICATIONS OF THE SPATIAL DISTRIBUTION OF MEANDER CUTOFFS ON THE RED RIVER (ND AND MN, USA)

The Red River was formed as Lake Agassiz drained ~10.5 kya, as the glaciolacustrine environment transitioned to a fluvial system. Little is known about the spatiotemporal history of the Red River’s meandering across the former lake bed. This work explores the spatial distribution of meander-cutoff features and notes their possible geomorphic connections. The geospatial distribution of meander cutoffs may point to reaches of relative stability, hydrologic impacts, spatial climate patterns, Glacial Isostatic Adjustments (GIA), or variations in sediment properties. Here, the geospatial distribution of meander cutoffs was evaluated using the Getis-Ord GI* Hot Spot Analysis, Grouping Analysis, and Linear Regression Tools within ESRI ArcMap 10.5. Results of the hot spot analysis show that meander cutoffs are spatially clustered in seven areas. The cutoffs display a skew toward the southern reaches of the Red River, with a skewness of 0.45. The seven hot spots contain 125 of the 160 cutoffs, and five of the seven hot spot clusters are south of Grand Forks, ND. Grouping analysis results show five distinctive groups that depend on topographic relief and distance from the present-day channel. Cutoffs that are closer to the modern channel path generally show a greater negative relief, which may point to a slight straightening of the channel during the Holocene. Regression analysis shows that there is a general relationship between the estimated amount of isostatic rebound and the latitude of cutoffs. Southern reaches of the river have rebounded less in comparison to northern reaches, and more meander cutoffs occur on the southern reaches of the Red River. This may suggest that channel entrenchment due to net land-surface uplift from isostatic rebound most significantly controls the occurrence of meander cutoffs in an otherwise heterogeneous geologic setting.