Application of Spectral Index-Based Logistic Regression to Detect Inland Water in the South Caucasus

James Worden,Jennifer Koch,Kirsten M. de Beurs,Braden C. Owsley

doi:10.3390/rs13245099

Abstract

The Caucasus is a diverse region with many climate zones that range from subtropical lowlands to mountainous alpine areas. The region is marked by irrigated croplands fed by irrigation canals, heavily vegetated wetlands, lakes, and reservoirs. In this study, we demonstrate the development of an improved surface water map based on a global water dataset to get a better understanding of the spatial distribution of small water bodies. First, we used the global water product from the European Commission Joint Research Center (JRC) to generate training data points by stratified random sampling. Next, we applied the optimal probability cut-off logistic regression model to develop surface water datasets for the entire Caucasus region, covering 19 Landsat tiles from May to October 2019. Finally, we used 6745 manually classified points (3261 non-water, 3484 water) to validate both the newly developed water dataset and the JRC global surface water dataset using an estimated proportion of area error matrix to evaluate accuracy. Our approach produced surface water extent maps with higher accuracy (89.2%) and detected 392 km2 more water than the global product (86.7% accuracy). We demonstrate that the newly developed method enables surface water detection of small ponds and lakes, flooded agricultural fields, and narrow irrigation channels, which are particularly important for mosquito-borne diseases.

Highlights

Since the different spectral indices perform differently depending on regional characteristics, we have previously evaluated four different water indices (NDWI, Modified NDWI (MNDWI), AWEIsh, AWEInsh) and a water detection method based on EVI, NDVI and MNWDI [31]
In a previous study [32], we evaluated NDWI, MNDWI, AWEIsh, AWEInsh, and a water classification algorithm based on NDVI/EVI and MNDWI to find surface water for three different study regions in the South Caucasus
Based on the three study regions in the South Caucasus studied in [32], we estimated that surface water occupied about 0.9% of the land surface in the South Caucasus

Summary

Introduction

The South Caucasus experienced significant land reform and privatization of the agricultural sector in the 1990s, which led to the segmentation of large agricultural plots into smaller private and commercially owned farms. This process, which left irrigation systems degraded in some agricultural areas [47,48,49], combined with post-Soviet conflicts in the region (most notably between Armenia and Azerbaijan) to create the ideal conditions for the resurgence of malaria that occurred from the mid-1990s to the early 2000s.

Results

Discussion

Conclusion