Analysis of changes in rivers planforms using google earth engine
Alejandro Tobón-Marín, Julio Cañón
Abstract
We use the computational capabilities of Google Earth Engine (GEE) to access and process different geospatial databases in order to generate a multiyear characterization of changes in rivers planforms. We develop the necessary code in GEE to delimit rivers at different scales using Landsat (Land Remote-Sensing Satellite (System)) and Sentinel images. We implement three different methods for delimiting rivers based on satellite information: the Normalized Difference Water Index (NDWI), the Modified Normalized Difference Water Index (MNDWI) and the Automated Water Extraction Index (AWEI). We apply these methods to annual mosaics generated for each source of information, and estimate rivers centerlines based on a thinning method. With the centerline and river planform delimitations, we automatically estimate three geomorphological indicators: mean width, connectivity and sinuosity. We apply our tool to analyse several reaches along eight representative Colombian rivers that exhibit different planforms and flow regimes, some of them correlated with the Southern Oscillation Index (SOI).