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Fundamental Flood Hazard Issues in the Alluvial Fan Environment
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
Alluvial plains occur at the toe of some active alluvial fans, but also occur along the axis of broad alluvial valleys or on piedmonts that have no active alluvial fans. In some cases, an alluvial plain is a transitional landform between alluvial fan landforms on an upper piedmont surface and the riverine floodplains of an axial valley stream system. Some of the defining characteristics of alluvial plains (ADWR, 1995) include the following: (1) smooth or gently undulating terrain with minimal lateral relief, with parallel rather than radial topographic contours, i.e., not having fan-shaped radial contour patterns; (2) lack of well-defined channels where flow is predominately non-channelized sheet flooding or shallow overbank flooding with non- or marginally erosive velocities; (3) high rates of flow attenuation to due extensive floodplain storage and infiltration; (4) uniform vegetative characteristics over the entire landform surface; and (5) fine-grained sediment substrate.
Remote Sensing and Gis Applications for Water Resources Planning in Micro-Watershed
Published in Balram Panigrahi, Megh R. Goyal, Modeling Methods and Practices in Soil and Water Engineering, 2017
P.K. Rout, J.C. Paul, B. Panigrahi
Alluvial Plain is a largely flat landform created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions, from which alluvial soil forms. A floodplain is part of the process, being the smaller area over which the rivers flood at a particular period of time, whereas the alluvial plain is the larger area representing the region over which the floodplains have shifted over geological time. The alluvial plain spreads an area about 177.12 ha which about 27.39% is of total area of the micro watershed. Groundwater potential is very good on these geographic units.Hills and plateaus
Groundwater Targeting Using Remote Sensing
Published in Prasad S. Thenkabail, Remote Sensing Handbook, 2015
Though most of the valley deposits have a simple vertical succession from coarse sands and gravel near the bottom of the channels to silts and clays at the top, the relative thickness of the coarse and fine units depends on the type of sediments carried by the river and the geologic history of the river and the point of interest. It is practical to visualize a large alluvial plain as a complex of more or less lens-shaped elongated bodies—or continuous layers—of gravel, sand, silt, and clay including various mixtures of these components. Figure 2.9 shows such a typical section through an alluvial plain and the successful and the unsuccessful wells depending on the sections pierced.
Assessment of channel shifting of Karnali Megafan in Nepal using remote sensing and GIS
Published in Annals of GIS, 2021
Biplob Rakhal, Tirtha Raj Adhikari, Sanjib Sharma, Ganesh R. Ghimire
There are five major geomorphological land units in the Karnali Megafan: present river channel, sand and gravel bars, active alluvial plain (low terrace), active alluvial plain (higher terrace) and recent alluvial plain (Table 1). The land units are differentiated by landscape characteristics (Carson, Shah, and Maharjan 1986). The present river channel is an active river course with alluvium bedload subjected to deep scouring and river bank instability during peak flow. The sand and gravel bars are active depositional landforms composed of clean sands and gravels subjected to frequent severe flooding. The active alluvial plain (low terrace) is an immediate flood plain composed of deposited alluvial materials and is subjected to severe river flooding. The active alluvial plains (higher terrace) are also depositional landform and occasionally flooded. The recent alluvial plains are the lower piedmont (depositional and erosional) floodplains used for cultivation, grazing and often for settlement purpose at higher elevations (Carson, Shah, and Maharjan 1986).