Geovisualization geoscience of large river floodplains

Figures & data

Figure 1. Sheet 13 (Plate 22) of the ‘Ancient Courses Mississippi River Meander Belt’ published by Fisk (1944). The legend in the top right corner shows the colour and pattern choice used by Fisk to present historical river courses (Source: Richards, unknown date).

Figure 2. Map of the study area with each area of interest (AOI) in southeastern Louisiana: Old River area, Morganza Floodway area, and Atchafalaya River.

Table 1. Details of data and maps applied in this study.

Data	Date/Source	Scale/Resolution	Format
Fisk Channel	Fisk, 1944	1:63300 (scanned file)	GeoTIFF
LiDAR points	Louisiana Statewide Lidar, Feb. 2003	Point spacing less than 3–4 m, point clouds has been edited to ground-only points	comma-separated values (CSV)
Hydrographical survey	Army Corps of Engineers, 2006 and 2007	1:10,000	design file (DGN)
Levee shapefile	Army Corps of Engineers, 2006	N/A	shapefile (.shp)

Figure 3. The cell value distributions and result maps for four classification methods. Here, Old River AOI is selected to demonstrate a variety of landforms and landscapes with different classification methods. In A through D, the y axis is the class number, and the x axis is the number of cells.

Figure 4. Landscapes and landforms of Old River AOI are discernible from coupled LiDAR-bathymetric data using a 50-class colour scheme design. Dashed rectangles indicate zoom in areas shown in Figure 8(A,B) and the solid line denotes the A-A’ profile shown in Figure 11.

Figure 5. Landscapes and landforms of the Morganza Floodway AOI are discernible from coupled LiDAR-bathymetric data using a 50-class colour scheme design. Dashed rectangle indicates zoom in area shown in Figure 8(C).

Figure 6. Landscapes and landforms of the middle Atchafalaya River AOI are discernible from coupled LiDAR-bathymetric data using a 50-class colour scheme design. Dashed rectangle indicates zoom in areas shown in Figure 9(A,B) and the solid lines denote the B-B’ and C-C’ profiles in shown Figure 11.

Figure 7. 3D model snapshots from CityEngine Web Scenes: (A), (B), (C) Old River AOI; (D), (E) Morganza Floodway AOI; and (F), (G) Atchafalaya River AOI.

Figure 8. Comparison of combined LiDAR and hydrographic survey DEM (∼2007 data) with parts of Fisk’s (1944) historical channel change maps.

Table 2. Geoscience learning from 2D and 3D renditions of the study area.

Site/Related Figures	Features and phenomena observed in 2D and 3D models
Old River (Figures 4, 7 and 8, Main Map, 3D link)	Scour zones in Old River Low Sill Channel where the structure was heavily damaged during the flood of 1973
	The geometry of the natural channels as compared with the varied artificial Old River inflow and outflow channels
	Dredge spoil, runny or reworked by floods
	Increased sedimentation/elevation inside levee boundaries or batture
	Relative elevations of active (Old River Outflow Channel), controlled (Old River navigation channel) and abandoned (Upper Old River) channels at junctures with the Red and Atchafalaya Rivers
Morganza (Figures 5, 7 and 8, Main Map, 3D link)	Alluvial and colluvial fans (Smith, 1996) at foot of upland
	Spatial variability in lake sedimentation of Raccouri Old River, an artificial cutoff formed in 1848
	The intersection of natural features (crevasse splays) with artificial ones (constructed levees)
Middle Atchafalaya (Figures 6 and 7, 9, Main Map, 3D link)	Sedimentation confined within both inner and outer levees as shown by differences in relative elevations
	Crevasses protruding onto backswamp
All (Figures 4–9, Main Map, 3D links)	Transition from natural levee to backswamp with increasing distance from the river
	Riffles and pools (bed variations) evident in large alluvial rivers
	Agricultural fields create subtle lines and polygons due to fences, vegetation placement, and subsidence associated with wetland drainage
	Dependence of south Louisiana on levees and structural mitigation
	Linear borrow areas (canals and long lakes) adjacent to artificial levees
	Other anthropogenic features including roads, railroads, spoil mounds, and well pads show higher relief than most natural features, impacting water flow and connectivity
Comparisons (Figures 3–8, Main Map, 3D links)	Between Mississippi and Atchafalaya: the older and historically more laterally active Mississippi River shows more extensive ridge and swale topography and abandoned channels
	Between Mississippi and Atchafalaya: dredge spoil mounds appear different from each other and differ in form from Apalachicola River (Mossa, Chen, Walls, Kondolf, & Wu, 2017), possibly due to reworking by floods and/or finer sediment in Mississippi
	Between Fisk and this paper: Fisk’s artistic paleochannels sometimes don’t match well with LiDAR
	Between Fisk and this paper: The anthropogenic imprint has become more dominant on this landscape since Fisk

Figure 9. Zoom-in view of natural and anthropogenic landforms in part of Atchafalaya River AOI (see Figure 6 for location).

Figure 10. Map of anthropogenic and natural floodplain features in which areas and volumes were quantified above a specific elevation: (A) and (B) parts of Old River AOI (above 15.5 masl); and (C) and (D) parts of Atchafalaya River AOI (above 5.9 masl).

Figure 11. Annotated floodplain cross sections for the Old River AOI (profile A-A’) and Atchafalaya River AOI (profiles B-B’ and C-C’). The locations of the profiles are shown in Figure 4 (profile A-A’) and 6 (profiles B-B’ and C-C’). Arbitrary floodplain elevations (dashed horizontal grey lines) were selected to estimate volumes of different types of anthropogenic and natural features.

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Richards, E. P. (Unknown). Louisiana geology. Retrieved from http://biotech.law.lsu.edu/climate/mississippi/fisk/fisk.htm

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Mossa, J., Chen, Y.-H., Walls, S. P., Kondolf, G. M., & Wu, C.-Y. (2017). Anthropogenic landforms and sediments from dredging and disposing sand along the Apalachicola River and its floodplain. Geomorphology, 294, 119–134. doi: 10.1016/j.geomorph.2017.03.010

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