Meander Migration Analysis in Southeastern US Rivers

Overview

This repository contains the code and results for a study quantifying meander migration dynamics in three Southeastern US rivers: the Yazoo River, the Ocmulgee River, and the Roanoke River. The study utilizes multi-temporal Landsat imagery and the Google Earth Engine (GEE) platform to extract river water bodies and their centerlines using the Medial Axis Transform. By analyzing the spatial changes in these centerlines over several decades, the research aims to quantify the rate and patterns of meander migration in these dynamic river systems.

Code

The primary code for this study is implemented in Google Earth Engine (GEE) and can be found in the gee_script.js file (or a similar name once you save your GEE script). This script performs the following steps:

1. Defines Study Areas: Specifies the geographical regions of interest for the Yazoo, Ocmulgee, and Roanoke Rivers.
2. Data Acquisition: Acquires multi-temporal Landsat Surface Reflectance imagery for the defined time periods (e.g., 1990, 2005, 2020).
3. Water Body Extraction: Implements the Modified Normalized Difference Water Index (MNDWI) and Otsu's thresholding method to extract water bodies from the Landsat imagery.
4. Centerline Extraction: Employs the Medial Axis Transform (using distance transform and local maxima) to extract the approximate centerline of the river channel from the water masks.
5. Channel Activity Calculation: Includes a simplified function to demonstrate the concept of calculating channel activity based on the extracted centerlines. Note: A more robust method for measuring lateral migration is required for accurate results.
6. Visualization (Optional): Provides code for visualizing the extracted water bodies and centerlines within the GEE environment.
7. Data Export (Optional): Includes code for exporting the water mask images and the extracted centerline vector data to Google Drive.

Data

The primary data source for this study is the Landsat satellite imagery available through the Google Earth Engine data catalog. The processed water masks and extracted centerlines (in vector format, e.g., Shapefile) will be stored in the data directory (or a similar location after exporting from GEE).

Results

The results directory will contain the quantitative results of the meander migration analysis, including:

• Tables: Summarizing the overall and (if implemented) segmental channel activity rates for each river and time period (e.g., in CSV or tabular format).
• Figures: Visualizations illustrating the meander migration patterns, such as overlays of centerlines from different years and maps showing the spatial distribution of channel activity rates along the river reaches. Example figures might include:
  • Maps showing the channel centerlines of the Yazoo River in 1990, 2005, and 2020, highlighting the lateral migration.
  • Graphs comparing the overall channel activity rates for the three rivers across the two time intervals (1990-2005 and 2005-2020).
  • Maps displaying the segmental channel activity along each river, with color gradients indicating the rate of migration.