Extraction of shoreline using Matlab

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Abstract

The Matlab code was developed for extracting the shoreline in our JGR-ES paper (Gao et al., 2019) and GRL paper (Gao et al., 2018), using the elevation results of Delft3D simulations. The procedures basically follow those proposed in Shaw et al. (2008).

Example

The numerical results of D3D

I exported the numerical results of D3D in the Quickplot module of D3D. To avoid exporting the data manually, which takes a lot a time, I used a Matlab script to export the data automatically. Then I split the “bulk” data (3 dimensions, 2 dimensions in space and 1 in time) into every single time step use a another code. Here is an example of the split data (2 dimensions in space), which I used for the further procedures.

Note:

  • Quickplot of D3D has lot of functions which I did not know before, however, I got familiar with thoes functions by firstly recording the Matlab code in the GUI of Quickplot.

Extracting the shoreline

Then I used the Matlab code to extract the shoreline:

  1. Put the Matlab code and the numerical results of D3D in the same path
  2. Run the Matlab function shoreline to get the shoreline

Note:

  • The notes in the Matlab code are currrently in Chinese, I will try to update.

Results

The extracted results are shown below:
Extracted shoreline
Figure 1. Procedures of the extraction of delta shoreline: (a) binary image of the bed level result where the white portion indicates bed level greater than 0 m, (b) minimum convex polygon of the cells with bed level greater than 0 m, (c) the potential shoreline grids marked as blue points, and (d) the extracted shoreline (yellow line).

References:

  1. Gao, W., D. Shao, Z. B. Wang, W. Nardin, P. Rajput, W. Yang, T. Sun and B. Cui (2019). Long-Term Cumulative Effects of Intra-Annual Variability of Unsteady River Discharge on the Progradation of Delta Lobes: A Modeling Perspective. Journal of Geophysical Research: Earth Surface, 124(4): 960-973.
  2. Gao, W., D. Shao, Z. B. Wang, W. Nardin, W. Yang, T. Sun and B. Cui (2018). Combined Effects of Unsteady River Discharges and Wave Conditions on River Mouth Bar Morphodynamics. Geophysical Research Letters, 45(23): 12,903-12,911.
  3. Shaw, J. B., Wolinsky, M. A., Paola, C., & Voller, V. R. (2008). An image-based method for shoreline mapping on complex coasts. Geophysical Research Letters, 35(12), L12405.