The Experts below are selected from a list of 8001 Experts worldwide ranked by ideXlab platform
Paola Passalacqua - One of the best experts on this subject based on the ideXlab platform.
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Automatic Channel Network Extraction From Remotely Sensed Images by Singularity Analysis
IEEE Geoscience and Remote Sensing Letters, 2015Co-Authors: Furkan Isikdogan, Alan C. Bovik, Paola PassalacquaAbstract:The quantitative analysis of Channel Networks plays an important role in river studies. To provide a quantitative representation of Channel Networks, we propose a new method that extracts Channels from remotely sensed images and estimates their widths. Our fully automated method is based on a recently proposed multiscale singularity index that strongly responds to curvilinear structures but weakly responds to edges. The algorithm produces a Channel map using a single image where water and nonwater pixels have contrast, such as a Landsat near-infrared band image or a water index defined on multiple bands. The proposed method provides a robust alternative to the procedures that are used in the remote sensing of fluvial geomorphology and makes the classification and analysis of Channel Networks easier. The source code of the algorithm is available at http://live.ece.utexas.edu/research/cne/ .
Yang Hong - One of the best experts on this subject based on the ideXlab platform.
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Construct Channel Network Topology From Remote Sensing Images by Morphology and Graph Analysis
IEEE Geoscience and Remote Sensing Letters, 2020Co-Authors: Xi Chen, Xinyi Shen, Yaokui Cui, Baojian Liu, Weizhen Fang, Qing Yang, Yang HongAbstract:Channel Network topology plays an important role in hydrological analysis. This letter proposes an innovative method to construct it based only on remote sensing images. The method uses spectral water indexes and mask of large lakes and ocean areas derived from remote sensing data to generate the map of Channels. Then, a morphological thinning algorithm is introduced to extract the initial skeleton of Channels. Moreover, an iterative pruning process based on a graph algorithm is proposed to simplify the initial skeleton. Finally, according to the simplified skeleton and its adjacency matrix, a new connectivity graph can be constructed to describe the Channel Network topology. The proposed method can construct complete skeleton structure and the topology of Channels with good connectivity in an automatic way. The output will facilitate detailed hydrological modeling and further applications.
Furkan Isikdogan - One of the best experts on this subject based on the ideXlab platform.
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Automatic Channel Network Extraction From Remotely Sensed Images by Singularity Analysis
IEEE Geoscience and Remote Sensing Letters, 2015Co-Authors: Furkan Isikdogan, Alan C. Bovik, Paola PassalacquaAbstract:The quantitative analysis of Channel Networks plays an important role in river studies. To provide a quantitative representation of Channel Networks, we propose a new method that extracts Channels from remotely sensed images and estimates their widths. Our fully automated method is based on a recently proposed multiscale singularity index that strongly responds to curvilinear structures but weakly responds to edges. The algorithm produces a Channel map using a single image where water and nonwater pixels have contrast, such as a Landsat near-infrared band image or a water index defined on multiple bands. The proposed method provides a robust alternative to the procedures that are used in the remote sensing of fluvial geomorphology and makes the classification and analysis of Channel Networks easier. The source code of the algorithm is available at http://live.ece.utexas.edu/research/cne/ .
Roger Moussa - One of the best experts on this subject based on the ideXlab platform.
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Invariant morphometric properties of headwater subcatchments
Water Resources Research, 2011Co-Authors: Roger Moussa, François Colin, Michael RabotinAbstract:The distinction between the Channel Network, the headwater subcatchments, and the lateral subcatchments plays an important role in distributed hydrological and ecohydrological applications. This paper presents some newly found invariance properties of headwater and upstream subcatchments and shows that the invariant morphometric properties characterize only natural Networks and virtual Networks verifying optimal Channel Networks (OCN) properties but are not verified for virtual non-OCNs. A model based on self-affine properties was developed in order to calculate the number of headwater catchments N and the total upstream area of headwater catchments U as a function of the cutoff area A used to delineate streams. For 18 French catchments between 43 and 116,450 km2 and for 4 virtual OCNs, results show that U(A)/A0 (with A0 being the catchment area) is independent of A for 0.5 < A < 5 km2 and seems to be constant (0.29 ± 0.03) for various shapes and sizes of Channel Networks and, consequently, can be considered as an invariant general descriptor of natural Channel and virtual OCN Networks. On the contrary, this is not the case when the approach is applied on six virtual non-OCNs. Moreover, results show that the knowledge of six morphometric indices enable us to calculate both functions N(A) and U(A) for all values of A < A0. These indices can be considered as geometric and topological properties of headwater and upstream subcatchments and are useful for studying the effects of cutoffs on self-affine river Networks or as similarity indices for Channel Network comparison.
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Definition of new equivalent indices of Horton-Strahler ratios for the derivation of the Geomorphological Instantaneous
Water Resources Research, 2009Co-Authors: Roger MoussaAbstract:The Horton-Strahler concept has been important in river basin geomorphology; it describes scaling properties and identifies GIUH but has also attracted criticisms, because it depends on the threshold area S, which is used to extract the Channel Network from digital elevation models (DEM), on the position of the outlet and on the few number of ratios used to identify the scaling laws. To overcome these limitations, this paper proposes new indices independently of S and which have similar properties than the Horton-Strahler ratios. Applications were conducted on seven French basins. The methodology consists on analyzing the morphometric properties, such as the drained area, the number of sources, and the length of the Channel Network as a function of S. The results show that Horton-Strahler ratios vary considerably with S. Particularly, while the W-order length LW is a staircase function of S, results show that the Channel Network is articulated around two main nodes independent of S, which are descriptors of LW. Then, we compared the properties of Horton-Strahler laws to those obtained from self-similarity analysis, which enables to define new indices independent of S. These indices are calculated automatically from DEM, have similar properties as the Horton-Strahler ratios, and are used to calculate the GIUH independently of S. The four new descriptors RBe, RLe, RAe, and Le, which have similar properties as RB, RL, RA, and LW respectively, are equivalent to those of Horton-Strahler’s laws and can be used as indicators of hydrological similarity for catchment comparison and regionalization
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What controls the width function shape, and can it be used for Channel Network comparison and regionalization?
Water Resources Research, 2008Co-Authors: Roger MoussaAbstract:[1] The width function captures the essential features of the catchment's GIUH's response. This paper aims to identify the morphometric properties which control the shape of the width function, and assess whether these properties can be used as similarity indices for catchment comparison. A new deterministic iterative model of the width function is proposed on the basis of a conceptualization of the topology of the Channel Network, and exploiting the morphometric characteristics of internal and external nodes. Tests are carried out on eleven French catchments and compared to the reference Peano catchment. Results show that the morphometric properties of three main internal and external nodes such as the drained area, the distance to the outlet, and the position on the Channel Network are useful descriptors for modeling the width function and for representing the scaling properties of a Channel Network. While the GIUHs based on Horton-Strahler ratios are strongly related to the method used to extract the Channel Network from the DEM, the new indices are independent of the method used. They are sufficient descriptors to reproduce the main shape of the width function, the peak, the time to peak, and the main properties such as non-negativity, non-stationarity, and power law decay of the spectrum. They may be used to establish catchment typology, to compare catchments, and to classify the width function peaks for catchment regionalization.
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Effect of Channel Network topology, basin segmentation and rainfall spatial distribution on the GIUH transfer function
Hydrological Processes, 2008Co-Authors: Roger MoussaAbstract:The hydrologic properties of the geomorphologic instantaneous Unit hydrograph (GIUH) are analysed as a function of the topological properties of the Channel Network and hillslopes, the hydraulic characteristics of flows (such as celerity and diffusivity), and the spatial distribution of effective rainfall. Applications were conducted on seven basins located in southern France. First, we study the effects of the spatial discretization of the catchment as a function of morphometric properties, such as the number of source points N, the total length of the Channel Network T and the mainstream length function M of the drained area S. Relationships are established between N(S), T(S) and M(S) and new descriptors are proposed and correlated with the hydrological properties of the GIUH. Results show that a subdivision of the basin into subcatchments determined by only two main nodes of the Channel Network is sufficient to identify the GIUH. Second, the sensitivity analysis shows that the GIUH is more sensitive to the Channel topology and to the spatial distribution of rainfall when correlated with altitude than it is to the hydraulic properties of flow on hillslopes and in the Channel. Numerical simulations enable one to compare the travel time on hillslopes and the travel time through the Channel Network as a function of the parameters of the GIUH, and to define constraints for basin segmentation in spatially distributed hydrological modelling
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on morphometric properties of basins scale effects and hydrological response
Hydrological Processes, 2003Co-Authors: Roger MoussaAbstract:One of the important problems in hydrology is the quantitative description of river system structure and the identification of relationships between geomorphological properties and hydrological response. Digital elevation models (DEMs) generally are used to delineate the basin's limits and to extract the Channel Network considering pixels draining an area greater than a threshold area S. In this paper, new catchment shape descriptors, the geometric characteristics of an equivalent ellipse that has the same centre of gravity, the same principal inertia axes, the same area and the same ratio of minimal inertia moment to maximal inertia moment as the basin, are proposed. They are applied in order to compare and classify the structure of seven basins located in southern France. These descriptors were correlated to hydrological properties of the basins' responses such as the lag time and the maximum amplitude of a geomorphological unit hydrograph calculated at the basin outlet by routing an impulse function through the Channel Network using the diffusive wave model. Then, we analysed the effects of the threshold area S on the topological structure of the Channel Network and on the evolution of the source catchment's shape. Simple models based on empirical relationships between the threshold S and the morphometric properties were established and new catchment shape indexes, independent of the observation scale S, were defined. This methodology is useful for geomorphologists dealing with the shape of source basins and for hydrologists dealing with the problem of scale effects on basin topology and on relationships between the basin morphometric properties and the hydrological response. Copyright © 2002 John Wiley & Sons, Ltd.
Xi Chen - One of the best experts on this subject based on the ideXlab platform.
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Construct Channel Network Topology From Remote Sensing Images by Morphology and Graph Analysis
IEEE Geoscience and Remote Sensing Letters, 2020Co-Authors: Xi Chen, Xinyi Shen, Yaokui Cui, Baojian Liu, Weizhen Fang, Qing Yang, Yang HongAbstract:Channel Network topology plays an important role in hydrological analysis. This letter proposes an innovative method to construct it based only on remote sensing images. The method uses spectral water indexes and mask of large lakes and ocean areas derived from remote sensing data to generate the map of Channels. Then, a morphological thinning algorithm is introduced to extract the initial skeleton of Channels. Moreover, an iterative pruning process based on a graph algorithm is proposed to simplify the initial skeleton. Finally, according to the simplified skeleton and its adjacency matrix, a new connectivity graph can be constructed to describe the Channel Network topology. The proposed method can construct complete skeleton structure and the topology of Channels with good connectivity in an automatic way. The output will facilitate detailed hydrological modeling and further applications.