Topographic change associated with floodplain mining activities in the Amite River, Louisiana

Abstract

Human activities, including mining, have altered landscapes for millenia. A location showing appreciable anthropogenic change is the middle Amite River and floodplain in southeastern Louisiana. Because of regional demand for construction and lack of other aggregate resources, gravel and sand mining began in the 1930s and has generally increased over the past century. Countless geomorphological alterations have occurred, including the creation of pits and ponds of diverse sizes and shapes. In this paper, we employed numerical methods to analyze changes in mining topology within the Middle Amite floodplain. Specifically, we utilized the Level Set Method (LSM), a numerical approach developed by Osher and Sethian in 1998, to assess surface curvature and shape. Additionally, the Localized Contour Tree (LCT) was applied to delineate mining depressions. Using LiDAR DEMs from 2005 to 2018, in a floodplain area of 9.6 km², the results indicate a marked increase in the number of pit depressions, rising from 163 to 289 and expanding of the depressions total area from 845.6 ha to 952.3 ha, with the most substantial growth observed in Reach D. , with notably, increase in the mean elevation ranges, particularly in Reach B, which saw depths grow from 1.3 m to 4.23 m. However, the volume storage showed an overall decline from ∼28.6 million m³ to ∼26.7 million m³, driven largely by a significant reduction in Reach E. The decrease in the storage capacities could be explained by the filling of the sedimentation of the pits over time, changes in the mining practices that may involve intentionally reducing pit volume capacity, other interactions within the floodplain environment such as pit captures contributing to the observed decrease in volume storage, or water level changes between the LiDAR imagery. implications of this study include the massive anthropogenic change in 13 years and decreases in floodplain water storage capacity, emphasizing the need for adaptive flood management strategies. These findings also provide practical guidance for environmental management and policy formulation, as the current state sand and gravel mining BMPs and buffer zones were inadequate to prevent pit captures the potential application of these methods elsewhere.