Historical Disturbance and Contemporary Floodplain Development along an Ozark River, Southwest Missouri

Abstract

The James River Basin (3,770 km2) in the Ozark Plateaus of Missouri was largely settled by the 1850s. However, little is known about how it responded to and recovered from early land disturbance. This study characterizes the distribution and thickness of historical overbank sedimentation along the upper James River through topographic surveys, subsurface floodplain sediment sampling, and historical aerial photo analysis. Stratigraphic markers used for this study include buried soils, metal tracers from mining operations, and cesium-137. Between 0.5 and 1 m of overbank deposition occurred on floodplains since settlement, with the highest rates coinciding with peak corn production in the late 1800s. A contemporary shelf has been developing in disturbance reaches since the 1880s. However, aerial photo records show that much of the channel has been stable since the 1950s. Current channel capacity at the floodplain stage is near the Q1.5 year flood, suggesting that it is adjusted to the current flood regime. However, the shelf forming below the floodplain stage in disturbance reaches may indicate that channels are still recovering from past disturbance. Apparently, Ozark rivers responded quickly to land disturbance, but recovery has lagged, perhaps due to decreased sediment loads following agricultural conversion to pasture and implementation of soil conservation practices.