Landscape change
The objective of the CLEAR landscape change module is to simulate the effects of different restoration scenarios on the amount of wetland area along the coast. The prediction is for 50 years into the future, and uses a combination of empirical relationships & landscape analogs to reflect the complex processes controlling land change in the Louisiana coastal zone. Primarily, simulations consist of land being converted to water through land loss processes or areas of open water being converted to land as a result of restoration projects.
The algorithms used in the CLEAR landscape change module are based on the growth rates & spatial dynamics of the Wax Lake delta in coastal Louisiana (shown below right). The diagram below on the left shows the input variables that are used to drive the calculations of land change over time.
.png "Linkages & interactions between the model input variables and effect on landscape change simulation.")
The algorithm for land building (from riverine diversions) is written such that grid cells are filled one by one in a fan pattern based on linear distance from the sediment source. This fan pattern mimicks the growth dynamics of the Wax Lake delta in coastal Louisiana. The numbers in the image below indicate the order in which the 500m x 500m grid cells would be filled with sediment, & therefore converted from water to land as a new delta is formed.
Land loss rates
Historic land loss rates from 1978 - 2000 are also applied to each cell in the coast wide grid; therefore, output from this module represents dynamic landscape change, not just land building. Loss rates are applied as averaged polygons across the coast. For more information about these data, please refer to:
Barras, J., S. Beville, D. Britsch, S. Hartley, S. Hawes, J. Johnston, P. Kemp, Q. Kinler, A. Martucci, J. Porthouse, D. Reed, K. Roy, S. Sapkota, and J. Suhayda. 2003. Historic and Predicted Coastal Louisiana Land Changes: 1978-2050. USGS Open File Report 03-334.
.jpg "Historic land loss rate polygons (from Barras et al. 2003).")
Model output
.jpg "Example output from the CLEAR landscape change module")
Output from the CLEAR landscape change module is given in 500m x 500m cells across coastal Louisiana from Mississippi to Texas. Output is given at 5-year time steps from Year 0 to Year 50. Finally, model output can be presented in a tabular format or mapped (as shown at left).
To view animations or download additional output maps from the CLEAR landscape change module, visit the CLEAR MapServer.
Model Comparisons & Sensitivity Analyses
The Wax Lake Delta Case Study compares the CLEAR landscape change module (Visser et al. 2008) to the geo-engineering model developed by Parker & Sequiros (2006). Both models are used to investigate delta building dynamics considering different sediment loads within the Wax Lake Outlet. Hydrographs from the last 25 years are applied to the CLEAR model & sediment load values (38 Mt/yr) are used in the geo-engineering model. These data are applied in 10% increments (10 – 200 %), and the resulting landscape change animations are provided at a 5-year time step (static maps at 10-year time step) through 100 years. The full set of animations, graphs & data values are provided in a CLEAR Google Maps application.
For more information on Landscape change, view these publications:
Land Building in the Delta of the Mississippi River: Is it Feasible?
Forecasting 50-Years of Landscape Change in Coastal Louisiana: No Increased Action & Preliminary Draft Master Plan
Coastal Louisiana Ecosystem Assessment & Restoration Program: The Role of Ecosystem Forecasting in Evaluating Restoration Planning in the Mississippi River Deltaic Plain
CLEAR Landscape Change Model
Predicting Land Building in the Mississippi Delta Plain: Knowledge & Uncertainty
Wetland Nourishment Module (now called landscape change)