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Geologic Principles
Published in Stephen M. Testa, Geological Aspects of Hazardous Waste Management, 2020
Alluvial fans are typically characterized by high permeability and porosity. Groundwater flow is commonly guided by paleochannels which serve as conduits, and relatively less permeable and porous debris and mud flow deposits. The preponderance of debris-flow and mudflow deposits in the medial portion of fans may result in decreased and less-predictable porosity and permeability in these areas. Aquifer characteristics vary significantly with the type of deposit and relative location within the fan. Pore space also develops as intergranular voids, interlaminar voids, bubble cavities, and desiccation cracks.
Delineation and mapping of palaeochannels using remote sensing, geophysical, and sedimentological techniques: A comprehensive approach
Published in Water Science, 2021
Ritambhara K. Upadhyay, Naval Kishore, Mukta Sharma
The methods available for palaeochannel studies are not only modern, but also noninvasive – such as optical and radar satellite imagery, GPR, electrical resistivity meter, remote sensing, LiDAR, which is coupled with the analysis of GIS and processing, and provides a suite of tools and methods for paleochannel identification, research, and mapping. The acknowledgment of advantages and limitations is essential to ensure successful research outcomes. Moreover, the combination of these methods with field ground-truthing methods such as visual observations, and ultimately subsurface core sampling analyses on the availability of resources is of great importance for the determination of the physical and chemical properties of palaeochannels.
Combining multi-source data to identify the paleochannel system in the saltwater intrusion area
Published in Marine Georesources & Geotechnology, 2023
Chao Jia, Kaifang Kong, Yue Yao, Xiao Yang, Deqiang Wang, Shuai Shao
Paleochannels are morphological material bodies of abandoned channels produced during the process of river changes. Paleochannels are influenced by a combination of structural movements, paleoclimatic and paleoenvironmental changes, hydrodynamic conditions and human activities. In recent years, with global climate change and rising average temperatures, changes in vegetation cover in some areas have led to catastrophic problems such as severe droughts and water scarcity, while global water demand is increasing, driven by population growth, expansion of irrigated farmland and economic development, and the growing demand for water and its temporal and spatial mismatch with water supply has made water scarcity a widespread problem around the world (Seager et al. 2007; Fischer, Knutti, and Beyerle 2013; Jaeger, Olden, and Pelland 2014; Irvine et al. 2017; Qi, Liu, and Leung 2019). Paleochannels are rich in underground freshwater resources and an essential water source for the shallow continental shelf and alluvial floodplain areas, a natural reservoir of atmospheric precipitation, surface water and groundwater, and a conduit for the transport of polluted groundwater (Sinha et al. 2013). The paleochannels are of great importance for land and water resource management (Samadder, Kumar, and Gupta 2011), paleoclimatic changes (Singh and Sinha 2019), mineral exploration (Rathore, Nathawat, and Champatiray 2010)and archaeological research (Karmanov et al. 2013). Many scholars have studied paleochannels. In the early years, the morphological characteristics, causes of formation and sedimentary evolution of paleochannels in the plains were studied mainly through topographic maps and a large number of boreholes to analyse the vertical changes of rock layers (Fielding et al. 2003; Francke 2012). However, these traditional methods are costly, cumbersome and not sufficiently accurate. With the advancement of modern technology, non-invasive remote sensing techniques are more often used to identify paleochannels (Samadder, Kumar, and Gupta 2011; Chaudhary and Aggarwal 2009; Mahammad and Islam 2021), and several image techniques and data processing techniques have been used to identify paleochannels, such as image classification (Rajani and Rajawat 2011), contrast enhancement (Mehdi et al. 2016), and spectral imaging technology (Resmi, Achyuthan, and Jaiswal 2017). However, many aerial photographs are severely distorted due to low spectral and spatial resolution, image degradation, the presence of obstructions (trees, artificial objects, etc.) and unfavourable preservation conditions (Lasaponara and Masini 2018), especially in places such as mountainous areas where paleochannels are often only partially visible (Luo et al. 2019). Infrared and thermal infrared scans can identify paleochannels using thermal image features obtained from the surface. Still, they can only scan small areas and some specific areas, and the images are strongly influenced by thermal radiation from the surrounding environment.