Abstract:

Google Earth photographs for January 1998, March 2004, October 2010, and February 2017 were used to measure the width of eleven backfilled and reference canals in coastal Louisiana marshes as part of a study investigating the impact of canal backfilling as a restoration technique.

Suggested Citation:

Turner, R. Eugene. 2018. Canal width measurements from backfilled and reference canals in coastal Louisiana marshes from four time points (1998, 2004, 2010, 2017). Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-7gs4-j475

Publications:

Turner, R. E., & McClenachan, G. (2018). Reversing wetland death from 35,000 cuts: Opportunities to restore Louisiana’s dredged canals. PLOS ONE, 13(12), e0207717. doi:10.1371/journal.pone.0207717

Purpose:

To determine changes in canal widths after backfilling.

Data Parameters and Units:

Worksheet: Locations - Site Number: User defined site identifier (assigned consistent with that in Neill C., Turner R.E. Backfilling canals to mitigate wetland dredging in Louisiana coastal marshes. Environmental Management (1987) 11: 823-836); Site Description: Location description for the study site; Parish: Louisiana parish in which the site is located; Quad: 15 minute quadrangle maps divided into four quadrats, starting at the upper left (A), upper right (B), lower left (C) and lower right (D); Lat.N. (decimal degrees): Latitude (N) of the study sites (Backfilled and Reference) in decimal degrees; Long.W. (decimal degrees): Longitude (W) of the study sites (Backfilled and Reference) in decimal degrees; Marsh Type: Classification of the marsh (Freshwater, Intermediate, Salt, Brackish); Plug: Status of the canal plug at the time measurements were made (Yes=canal was originally plugged when it was backfilled; No=canal was not plugged when it was backfilled; Gone=canal was listed as plugged, but evidence of a plug was not present in the most recent aerial imagery; Intact=Original plug still intact; Breached=Original plug breached in some way); Year Dredged: Year that the canal was dredged, in decimal format; Year Backfilled: Year that the canal was backfilled, in decimal format. Worksheet: Measurements - Measurements of canal widths (in meters) for reference (REF) and backfilled (BF) canals over four mapping intervals (1998, 2004, 2010, 2017). Data is organized by Site and presented for eleven distances (m along transect: 0.00, 20.00, 40.00, 60.00, 80.00, 100.00, 120.00, 140.00, 160.00, 180.00, 200.00) parallel to the spoil bank. M on Map: Distance of each canal transect, as defined by the Google measurement tool (target was minimum 200 meters).

Methods:

Using the measuring tool in Google Earth, a 200 m transect was placed within each canal starting 10-20 m before the keyhole feature at its terminal end and extending towards the canal entrance at the connecting waterway. The transect was segmented into 10 equally spaced sub-sections and the widths measured at the 11 perpendicular transect lines (0.00, 20.00, 40.00, 60.00, 80.00, 100.00, 120.00, 140.00, 160.00, 180.00, 200.00 meters). Reference measurements were made using the same methods in nearby canals that met these criteria: 1) minimum of 200 m in length, 2) were not backfilled, and 3) appeared abandoned based on the absence of physical structures within the canal.

Individual Files: