The use of satellite remote sensing for exploring river meander migration
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Abstract:
Meandering rivers are complex systems that support high rates of biodiversity and the livelihoods of millions of inhabitants through their ecological services. Meandering rivers are often located in remote locations and cover long distances. As a result, observational satellites are crucial for investigating and monitoring meandering river dynamics. Satellite remote sensing technology is responsible for many advances in our knowledge about the variables that affect these rivers and their interaction with their surrounding floodplains. Furthermore, new sensors and the advent of cloud computing are allowing researchers to revisit theories that have hitherto lacked observational evidence to support them. In this paper, we review articles that have applied remote sensing techniques to analyse river meander migration processes. Our findings show that the majority of articles analysed the meandering rivers of the Ganges/Brahmaputra (29.0% of all articles) and the Amazon Basin (26.1%). We propose that these two locations are popular for different reasons: to improve management in highly populated floodplains of Ganges/Brahmaputra, and to investigate the meandering mechanisms without major anthropogenic interference in the Amazon Basin. Furthermore, most of the articles used Landsat for river monitoring (80.7%) and tracked the river changes throughout time using satellite time series (82.0%). However, the incorporation of Synthetic Aperture Radar satellites in papers was minimal, and only a small fraction (13%) of studies utilized cloud computing platforms for processing satellite images. Finally, we discuss new possibilities in terms of sensors and processing that might in the future advance our knowledge of river geomorphology.Keywords:
Meander (mathematics)
This research deals with the surface dynamics and key factors – hydrological regime, sediment load, and erodibility of floodplain facies – of frequent channel shifting, intensive meandering, and lateral instability of the Bhagirathi River in the western part of the Ganga-Brahmaputra Delta (GBD). At present, the floodplain of the Bhagirathi is categorized as a medium energy (specific stream power of 10–300 W m−2), non-cohesive floodplain, which exhibits a mixed-load and a meandering channel, an entrenchment ratio >2.2, width–depth ratio >12, sinuosity >1.4, and channel slope <0.02. In the study area, since 1975, four meander cutoffs have been shaped at an average rate of one in every 9–10 years. In the active meander belt and sand-silt dominated floodplains of GBD, frequent shifting of the channel and meander migration escalate severe bank erosion (e.g. 2.5 × 106 m3 of land lost between 1999 and 2004) throughout the year. Remote sensing based spatio-temporal analysis and stratigraphic analysis reveal that the impact of the Farakka barrage, completed in 1975, is not the sole factor of downstream channel oscillation; rather, hydrogeomorphic instability induced by the Ajay–Mayurakshi fluvial system and the erodibility of floodplain sediments control the channel dynamics of the study area.
Meander (mathematics)
Sinuosity
Bank erosion
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The 100-year floodplain is the traditional indicator of flood risk and the area in which specific flood mitigation requirements are required to occur in the United States. However, recent studies have indicated that there is a growing disconnect between the 100-year floodplain and the location of actual losses. As a result, there is a strong need to understand what is undermining the efficacy of the 100-year floodplain and to generate a more accurate depiction of flood risk. However, there have been few studies that examine the characteristics of insured flood claims occurring outside the 100-year floodplain and how more advanced hydrologic models may improve flood risk delineation. This study addresses this issue by cross-validating a fairly new distributed hydrologic flood inundation model and the Federal Emergency Management Association's 100-year floodplain with historical, parcel-level insured flood losses in two subbasins near Houston, Texas. Results illustrate that spatially distributed hydrologic models greatly improve floodplain delineation, provide important insights on the drivers of flood damage outside of the floodplain, and offer alternative ways to more effectively communicate flood risk.
Flood insurance
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Summary Three-dimensional coastal exposures of the Middle Jurassic (Bathonian) Scalby Formation in Yorkshire, England, exhibit a complex, exhumed meander belt. The lateral accretion surfaces (epsilon-cross stratification) of individual meander loops are described. Field and aerial photograph measurements of accretion-surface dimensions have enabled direct determination of channel bankful depths and widths and meander wavelengths. Values for mean annual discharge of the channel system are derived using existing empirical equations. Palaeocurrents measured in the meander belt sandstones show a wide dispersal due to many periods of meander migration and cut off.
Meander (mathematics)
Stratification (seeds)
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Meander (mathematics)
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