Relationship of dredged canals and wetland loss in Louisiana

The direct effects of converting wetlands to open water by dredging can be magnified by indirect effects. For example, the dredged canal allows for recovery of mineral fluids 1000s of m belowground which may induce geological subsidence or faulting; dredged material deposited at the surface to form continuous levees may create hydrologic stressors on the wetland plants resulting in a conversion to open water habitat as a result of both soil waterlogging and drying, less organic matter and sediment accumulation, or greater erosion. We quantified indirect effects by demonstrating a robust dose-response relationship between coastal land loss and dredging canals in the Mississippi and Niger river deltas over 60 years. Importantly, the ratio of land loss to canal area increases with time – a legacy effect. We also found that flood protection levees on the main channel did not magnify the effect of dredging on wetland loss by inhibiting sediment flow into adjacent wetlands along its banks., Published and unpublished data are reported for digitized areas of land and canal for 15' and 7.5' maps in the Louisiana coastal zone. No transformations of the data were done., , # **Percent dredged canal density and wetland loss in Louisiana**

[https://doi.org/10.5061/dryad.sn02v6x9s](https://doi.org/10.5061/dryad.sn02v6x9s)

The dose-response relationships between the percent dredged canals and percent land loss in Louisiana and Nigeria coastal zone were quantified using land and water data. Published data in 7.5' and 15' quadrangle maps for the Louisiana deltaic coastal zone from 1932 to 1990 are included in this data file as well as some unpublished data records. The %land loss relative to the baseline land area at the start of the interval was calculated. A direct relationship between dredged area and land to water conversion is demonstrated that accelerates over decades.

## Description of the data and file structure

The data are in an excel spreadsheet accompanied by location maps for the Louisiana coast.
The units for the area of land and water are 'acres' (the original reporting units).
The percent land or percent canal in maps of different dates ar...