Exploring the channel connectivity structure of the August 2008 avulsion belt of the Kosi River, India: Application to flood risk assessment
TL;DR: In this paper, the authors use a topography-driven connectivity model to simulate the avulsion pathway, which corresponds to that observed in the post-avulsion period, and then use this model to postulate the avulsive course of the river from another upstream point based on avulsion threshold analysis.
Abstract: The August 2008 avulsion of the Kosi River, northern India, resulted in a maximum eastward shift of >100 km and created an avulsion belt of 2722 km2. Based on A.D. 2000 Shuttle Radar Topography Mission data and on 2005 Landsat Thematic Mapper satellite image–derived channel network (pre-avulsion), we use a topography-driven connectivity model to simulate the avulsion pathway, which corresponds, to a large extent, to that observed in the post-avulsion period. We then use this model to postulate the avulsive course of the river from another upstream point based on avulsion threshold analysis. Our results demonstrate that this model has the potential for postulating the path of an avulsive channel, and can provide a priori information on the areas likely to be flooded following an embankment breach.
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TL;DR: This paper explored the effects of seasonal and yearly variable rainfall and the resultant highly peaked discharge pattern on river morphodynamics, and presented a comparison of modern and ancient monsoonal and subtropical river deposits, by documenting the diversity of the sedimentary facies, macroforms (bar forms), and architectural elements common in ancient and modern monsoon-controlled rivers.
127 citations
TL;DR: In this paper, Geomorphological, hydrological, and socioeconomic data have been integrated in a GIS framework using a multi-criteria decision tool called the Analytical Hierarchy Process (AHP) to generate a process-based flood risk map for 105 blocks (administrative units) of both Nepal and India (Bihar).
97 citations
TL;DR: In this article, the authors compared the relative efficiency of two flood zonation methods, the frequency ratio and fuzzy logic models, for flood susceptibility evaluation and delineation in the Kosi megafan region of eastern Bihar, India.
Abstract: The Kosi megafan region of eastern Bihar, India, comprising of eight districts, is regularly afflicted by large floods that cause extensive damage. Mapping the possible inundation susceptible zones in the region accurately is, therefore, paramount for land resource conservation and livelihood preservation. This paper compares the relative efficiency of two flood zonation methods, the frequency ratio and fuzzy logic models, for flood susceptibility evaluation and delineation. Flooded extents from two past events were combined to create the training dataset, which was then compared individually with respective maps of 12 well-documented causal factors of inundation to gauge their relative influence on the flood spread. These were merged using the two models to generate the respective flood susceptibility maps, which were subsequently validated using the Receiver Operating Characteristics Curve and the Seed Cell Area Index methods. Results revealed that an enhanced fuzzy logic model (prepared by assigning relative weights to the respective causal factors as obtained from their analysis in the frequency ratio model) was more accurate and robust in demarcating flood susceptibility zones, as was further ascertained by comparison with a recent flood event, thereby providing a novel way to merge these methods. The western and southern tracts of the region were found to be more inundation prone, with the greatest risk posed along the narrow interfluve between the Kosi and Ganga rivers prior to their confluence further east. The districts most likely to be inundated were identified by computing their respective proportionate areas under the very highly susceptible flood class.
80 citations
TL;DR: In this paper, the authors used the SRTM-based digital elevation model and remotely sensed data coupled with field topographic mapping with a kinematic GPS and a Total Station to characterise a ~ 50 km-long stretch of the Kosi River.
68 citations
Cites background from "Exploring the channel connectivity ..."
...This breach resulted in amajor avulsion of the Kosi River, which shifted by ~120 km eastward — one of the greatest avulsions in a large river in recent years (Mishra, 2008; Sinha, 2009; Kale, 2011; Sinha et al., 2013)....
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...Sinha et al. (2013) also postulated the avulsive course of the Kosi from one of the potential sites for avulsion identified in this paper (reach 4)....
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...In a recent work, Sinha et al. (2013) analysed the channel connectivity structure of the Kosi (D) Avulsed course 26° 87° 87° false colour composite of Landsat image of 2003 showing the Kosi River basin, (C) detailed 003), (D) detailed view of the study area showing the Kosi River during the…...
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...Our analysis of the connectivity structure for the pre- and postavulsion period (Sinha et al., 2013) has shown that the ‘structural’ connectivity of the paleochannel network on the fan surface provided the pathway for the avulsion channel during the August 2008 event....
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TL;DR: It is argued that IC model can be extremely beneficial to understand sediment dynamics at catchment scale in a large river basin (~103-104 km2 scale), where systematic field investigations for mapping hillslope-channel linkages are not feasible.
60 citations
References
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TL;DR: The normalized difference water index (NDWI) as discussed by the authors was proposed for remote sensing of vegetation liquid water from space, which is defined as (ϱ(0.86 μm) − ϱ(1.24 μm)) where ϱ represents the radiance in reflectance units.
4,461 citations
TL;DR: The Normalized Difference Water Index (NDWI) as mentioned in this paper is a new method that has been developed to delineate open water features and enhance their presence in remotely-sensed digital imagery.
Abstract: The Normalized Difference Water Index (NDWI) is a new method that has been developed to delineate open water features and enhance their presence in remotely-sensed digital imagery. The NDWI makes use of reflected near-infrared radiation and visible green light to enhance the presence of such features while eliminating the presence of soil and terrestrial vegetation features. It is suggested that the NDWI may also provide researchers with turbidity estimations of water bodies using remotely-sensed digital data.
4,353 citations
"Exploring the channel connectivity ..." refers methods in this paper
...A normalized difference water index (NDWI) was calculated, as it helps to delineate the surface-water features more accurately (McFeeters, 1996)....
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TL;DR: The NASA/NGA Shuttle Radar Topography Mission (SRTM) collected interferometric radar data which has been used by the Jet Propulsion Laboratory to generate a near-global topography data product for latitudes smaller than 60° as mentioned in this paper.
Abstract: The NASA/NGA Shuttle Radar Topography Mission (SRTM) collected interferometric radar data which has been used by the Jet Propulsion Laboratory to generate a near-global topography data product for latitudes smaller than 60°. One of the primary goals of the mission was to produce a data set that was globally consistent and with quantified errors. To achieve this goal, an extensive global ground campaign was conducted by NGA and NASA to collect ground truth that would allow for the global validation of this unique data set. This paper documents the results of this SRTM validation effort using this global data set. The table shown below summarizes our results (all quantities represent 90 percent errors in meters).
906 citations
TL;DR: An overview of how existing research relates to the concept of connectivity in both ecology and hydrology is provided by proposing and evaluating a conceptual model of hydrological connectivity that includes five major components: climate; hillslope runoff potential; landscape position; delivery pathway and lateral connectivity.
Abstract: The term 'connectivity' is increasingly being applied in hydrological and geomorphological studies. Relevant research encompasses aspects of landscape connectivity, hydrological connectivity and sedimentological connectivity. Unlike other disciplines, notably ecology, published studies show no consensus on a standard definition. This paper provides an overview of how existing research relates to the concept of connectivity in both ecology and hydrology by proposing and evaluating a conceptual model of hydrological connectivity that includes five major components: climate; hillslope runoff potential; landscape position; delivery pathway and lateral connectivity. We also evaluate a proposed measure of connectivity called the volume to breakthrough to quantify changing connectivity between different environments and catchments.
727 citations
TL;DR: In this paper, a refinement which distinguishes structural connectivity from functional connectivity can be used to explain patterns observed in very different environmental systems, such as linkages between surface and subsurface flowpaths and the hyporheos in the River Don, a temperate river channel in Yorkshire, UK; in surface and surface fluxes in agricultural land in UK; and in vegetation and surface conditions in a degrading environment at the Sevilleta LTER site in the semi-arid Southwest USA.
264 citations
"Exploring the channel connectivity ..." refers background in this paper
...Class I represents an example of dry paleochannel with full structural connectivity (Wainwright et al., 2011) but with no functional connectivity, whereas class III represents an active channel with full structural and functional connectivity (Bracken and Croke; 2007; Wainwright et al., 2011)....
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