Impact of Dam on River Depth and Floodplain Inundation

Keywords: Human activities, HEC-RAS, DEM, Riverbed elevation, LiDAR
Abstract Type: Paper Abstract

Abstract

Rivers and their floodplain are landscape features that are dynamically complex in nature. Their dynamism is based on constant morphological changes by floods at various spatial and temporal scales. Human alterations to riverscape, such as flow regulation through dams, can lead to changes in sediment supply with indirect influence on flood pulse, resulting in lateral disconnectivity of the river system. This research assessed the Upper Apalachicola River depths and floodplain inundation between the early post-dam and late post-dam periods downstream of Jim Woodruff dam. Hydrographic data for 1960 and 2010 were collected from the US Army Corps of Engineers. A ≤ 1.2 m LiDAR point cloud covering the entire river was combined with the hydrographic data. The combined data was converted into riverbed elevation (including a digital elevation model—DEM ) through the forward and inverse transformation between cartesian and channel-centered coordinate systems. Daily discharge data and stage data (1958—2010) were collected for Chattahoochee and Blountstown stations. Flows of the 99th, 74th, 48th, 21st, and 1st percentile were determined using the flow duration curve from the daily discharge data. The flow, stage, DEM, and Manning n roughness coefficients served as input variables to a 2D hydrodynamic model, HEC-RAS—used to model the river depth and floodplain inundation. The result showed an increase in river depth with a median value of 2m and a decrease in floodplain inundation. The result is critical for river management, conversation, and policy formulation for rivers in the Anthropocene.