Abstract
Wadis, ephemeral dry rivers in arid desert regions that contain water in the rainy season, are often manifested as braided linear channels and are of vital importance for local hydrological environments and regional hydrological management. Conventional methods for effectively delineating wadis from heterogeneous backgrounds are limited for the following reasons: (1) the occurrence of numerous morphological irregularities which disqualify methods based on physical shape; (2) inconspicuous spectral contrast with backgrounds, resulting in frequent false alarms; and (3) the extreme complexity of wadi systems, with numerous tiny tributaries characterized by spectral anisotropy, resulting in a conflict between global and local accuracy. To overcome these difficulties, an automated method for extracting wadis (AMEW) from Landsat-8 Operational Land Imagery (OLI) was developed in order to take advantage of the complementarity between Water Indices (WIs), which is a technique of mathematically combining different bands to enhance water bodies and suppress backgrounds, and image processing technologies in the morphological field involving multi-scale Gaussian matched filtering and a local adaptive threshold segmentation. Evaluation of the AMEW was carried out in representative areas deliberately selected from Jordan, SW Arabian Peninsula in order to ensure a rigorous assessment. Experimental results indicate that the AMEW achieved considerably higher accuracy than other effective extraction methods in terms of visual inspection and statistical comparison, with an overall accuracy of up to 95.05% for the entire area. In addition, the AMEW (based on the New Water Index (NWI)) achieved higher accuracy than other methods (the maximum likelihood classifier and the support vector machine classifier) used for bulk wadi extraction.
Highlights
Arid regions are crucial areas for the study of global environmental change and sustainable development, and contain environment-specific habitats for both humans and natural species [1,2,3].desertification and water shortages caused by continuously decreasing precipitation in arid regions are a serious problem leading to a cascade of ecological and environmental problems [4,5,6,7].The term “wadi,” in Arabic, refers to a valley-like landscape, commonly found in and around desert regions
The results indicate that the automated method for extracting wadis (AMEW) is capable of identifying most of the narrow wadis but performed comparatively poorly in the case of wide wadis
Wadis are a valuable water resource in desert regions, and their accurate mapping and monitoring is of great importance for regional hydrological management and utilization
Summary
Arid regions are crucial areas for the study of global environmental change and sustainable development, and contain environment-specific habitats for both humans and natural species [1,2,3]. The term “wadi,” in Arabic, refers to a valley-like landscape, commonly found in and around desert regions. They are ephemerally filled with water from heavy rainfall in the rainy season, resulting in a Remote Sens. As one of the main river types in arid regions, the distribution and variation of wadis in these dry regions play a vital role in maintaining the health of the ecological environment and biological diversity, but they have a significant impact on the sustainable development of human society and economy. Considering the intermittently available sub-surface water contained within them, wadis are to some extent associated with the centers of local population [8]
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