On the morphology of radial sand ridges     

Weina Zhang  Xiaohe Zhang  Huiming Huang  Yigang Wang  Sergio Fagherazzi 《地球表面变化过程与地形》2020,45(11):2613-2630

We use a hydrodynamic model applied to an idealized fan-shaped basin to explore the morphology and dynamics of radial sand ridges in a convergent coastal system. A positive morphological feedback between channel incision and flow redistribution is responsible for the formation of the channel-ridge pattern. The selection mechanism of bottom wavelength is associated with flow concentration in the deeper part of the channels. Our results are compared to sediment and hydraulic dynamics in the radial sand ridges (RSRs) in China. In a convergent, sloping basin the tangentially averaged tidal velocity peaks at 47 km from the apex. This distance is similar to the arc distance, 62 km, where the RSRs are most incised. An offshore shift in tidal phase results in stronger flows near the north coastline, explaining the presence of asymmetric channel patterns. A numerical stability analysis indicates that small radial oscillations with a wavelength of 10° to 15° maximize the velocity in the troughs. This oscillation wavelength also emerges in the RSRs, which display a peak in spectral energy at a radial wavelength between 25° to 37.5°. High-resolution numerical simulations in the RSRs confirm that flow concentration occurs in the deeper part of the channels, keeping them flushed. We therefore conclude that the RSRs display morphometric characteristics similar to other tidal incisions, like tidal inlets and intertidal channels. This result further supports the dominant role of tidal prism and related peak velocities in incising coastal landscapes. © 2020 John Wiley & Sons, Ltd.  相似文献   

Contamination source detection in water distribution networks using belief propagation     

Ortega  Ernesto  Braunstein  Alfredo  Lage-Castellanos  Alejandro 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(3):493-511

Stochastic Environmental Research and Risk Assessment - We present a Bayesian approach for the Contamination Source Detection problem in water distribution networks. Assuming that contamination is...  相似文献   

Active Crustal Deformation in the Area of San Carlos,Baja California Sur,Mexico as Shown by Data of Local Earthquake Sequences     

Luis Munguía  Mario González-Escobar  Miguel Navarro  Tito Valdez  Sergio Mayer  Alfredo Aguirre  Victor Wong  Manuel Luna 《Pure and Applied Geophysics》2016,173(10-11):3631-3644

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Waste Gaseous Streams: From Environmental Issue to Source of Water by Using Membrane Condensers          下载免费PDF全文

Adele Brunetti  Sergio Santoro  Francesca Macedonio  Alberto Figoli  Enrico Drioli  Giuseppe Barbieri 《洁净——土壤、空气、水》2014,42(8):1145-1153

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Back‐barrier flooding by storm surges and overland flow     

Sergio Fagherazzi  Anthony M. Priestas 《地球表面变化过程与地形》2012,37(4):400-410

Low‐elevation areas within a sandy barrier island are subject to flooding via saturation overland flow following moderate storm surges and rainfall events. Using a high resolution topographic survey and simple hydrology models, we estimate the discharge and velocities from storm surge return flow and saturation overland flow. Results show that return flow velocities are of the same magnitude as the critical velocity necessary to mobilize sand when a hydraulic connection between the watershed and back‐barrier bay is present. Storms of moderate strength and rainfall intensity may be sufficient to keep the return channels open within the back‐barrier, thus providing natural conduits for water exchange from overwash events during extreme storm surges triggered by hurricanes. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

PERPETUATE guidelines for seismic performance-based assessment of cultural heritage masonry structures   总被引：1，自引：1，他引：0  

Sergio Lagomarsino  Serena Cattari 《Bulletin of Earthquake Engineering》2015,13(1):13-47

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Earthquake dynamics on circular faults: a review 1970–2015     

Raul Madariaga  Sergio Ruiz 《Journal of Seismology》2016,20(4):1235-1252

We review the development of earthquake dynamics taken from the point of view of the origin of seismic radiation instead of the detailed study of rupture propagation on complex surfaces. Many features of seismic radiation can be explained by simple models that serve as elementary canonical problems. Some of these properties are very well known like the fact that at low frequencies, the seismic spectrum is proportional to the seismic moment. At high frequencies, on the other hand, radiation is generated by the motion of the rupture front, in particular stopping phases and geometrical obstacles (barriers). A rupture front moving at constant speed does not produce far-field radiation. For many practical applications, for determining source size and stress drop, for example, it is not necessary to determine geometrical details of the rupture. For such cases, a simple circular crack model is quite sufficient. An improvement on this method is to do dynamic inversion on simple, elliptical-shaped sources and letting the rupture start arbitrarily from a point on the fault. This problem can be solved nowadays with finite differences and a variety of inversion techniques.  相似文献   

Dynamics of a fringe mangrove forest detected by Landsat images in the Mekong River Delta,Vietnam          下载免费PDF全文

William Nardin  Silvia Locatelli  Valerie Pasquarella  Maria Cristina Rulli  Curtis E. Woodcock  Sergio Fagherazzi 《地球表面变化过程与地形》2016,41(14):2024-2037

Mangrove forests dominate many tropical coastlines and are one of the most bio‐diverse and productive environments on Earth. However, little is known of the large‐scale dynamics of mangrove canopies and how they colonize intertidal areas. Here we focus on a fringe mangrove forest located in the Mekong River Delta, Vietnam; a fast prograding shoreline where mangroves are encroaching tidal flats. The spatial and temporal evolution of the mangrove canopy is studied using a time series of Landsat images spanning two decades as well as Shuttle Radar Topography Mission (SRTM) elevation data. Our results show that fast mangrove expansion is followed by an increase in Normalized Difference Vegetation Index (NDVI) in the newly established canopy. We observe three different dynamics of the mangrove fringe: in the southwest part of the fringe, near a deltaic distributary where the fringe boundary is linear, the canopy expands uniformly on the tidal flats with a high colonization rate and high NDVI values. In the northeast part of the fringe, near another distributary, the canopy expands at a much lower rate with low NDVI values. In the fringe center, far from the river mouths, the fringe boundary is highly irregular and mangroves expansion in characterized by sparse vegetated patches displaying low NDVI values. We ascribe these different dynamics to wave action and southwest longshore transport triggered by energetic northeasterly monsoons during winter. We further link the large‐scale dynamics of the fringe to small‐scale physical disturbances (waves, erosion and deposition) that might prevent the establishment of mangrove seedlings. Based on these results, we include mangrove encroachment in an already published conceptual model of progradation of the Mekong River Delta. We conclude that high NDVI values and a constantly linear vegetation–water interface are indicative of stable mangrove canopies undergoing fast expansion, probably triggered by sediment availability at the shore. Our results can be applied more generally to mangrove forests growing in minerogenic and high tidal range environments with high sediment inputs. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Montecarlo DLA-type simulations of wetting effects in fluid displacement in porous media     

Rafael Rangel  Sergio Rojas 《Computational Geosciences》2009,13(2):215-225

In this work, we report diffusion-limited aggregation (DLA)-type Montecarlo computations of a stochastic model of displacement of a viscous fluid by another that preferentially wets a porous medium, for the case when both fluids are immiscible in the absence of buoyancy forces. The model has the aim to simulate cooperative invasion processes found in experiments of immiscible wetting displacement. The model considers the nonlocal effects of the Laplacian pressure field and the capillary forces via hydrodynamic equations in the Darcy regime with a boundary condition for the pressure at the interface. The boundary condition contains two different types of disorder: the capillary term, which constitutes an additive random disorder, and a term containing an effective random surface tension, which couples to a curvature (it constitutes a multiplicative random term that carries nonlocal information of the whole pressure). We generate different displacement patterns for different setting of the parameters of the model. We analyze these patterns by studying the scaling properties of the interface that separate the two fluids and calculating the fractal dimension of the interface. The results show the existence of three distinct regimes of scaling. One regime at the smallest-length scales is due to the multiplicative random disorder together with the nonlocal coupling; it reveals itself in a roughness exponent α ≈ 0.80. Additionally, we find a DLA-type scaling regime with a roughness exponent α ≈ 0.60 at the largest scales and intermediate scaling regime with α ≈ 0.70 corresponding to invasion percolation with trapping. Each regime has definite scaling ranges that depend on the capillary number and the relative wetting tendency of the fluids. The behavior of the fractal dimensions of the interfaces of the aggregates constitutes a further confirmation of the existence of three scaling regimes and the multi-self-affinity of the perimeter of the interface boundaries.  相似文献   

The contrasted evolution of high and low flows and precipitation indices in the Duero basin (Spain)     

Enrique Morán-Tejeda  Juan Ignacio López-Moreno  Sergio M. Vicente-Serrano  Jorge Lorenzo-Lacruz  Antonio Ceballos-Barbancho 《水文科学杂志》2013,58(4):591-611

Abstract

Trends in high and low flows are valuable indicators of hydrological change because they highlight changes in various parts of the frequency distribution of streamflow series. This enables improved assessment of water availability in regions with high seasonal and inter-annual variability. There has been a substantial reduction in water resources in the Duero basin (Iberian Peninsula, Spain) and other areas of the Mediterranean region during the last 50 years, and this is likely to continue because of climate change. In this study, we investigated the evolution and trends in high and low flows in the Spanish part of the Duero basin, and in equivalent or closely-related precipitation indices for the period 1961–2005. The results showed a general trend of decrease in the frequency and magnitude of high flows throughout most of the basin. Moreover, the number of days with low flows significantly increased over this period. No clear relationship was evident between the evolution of high/low flows and changes in the distribution frequencies of the precipitation series. In contrast to what was expected, the number of days with heavy precipitation and the mean annual precipitation did not show significant trends across the basin, and the number of days without rainfall decreased slightly. The divergence between precipitation and runoff evolution was more accentuated in spring and summer. In the absence of trends in precipitation, it is possible that reforestation processes in the region, and increasing temperatures in recent decades, could be related to the decreasing frequency of high flows and the increasing frequency of low flows.

Editor Z.W. Kundzewicz; Associate editor S. Grimaldi

Citation Morán-Tejeda, E., López-Moreno, J.I., Vicente-Serrano, S.M., Lorenzo-Lacruz, J. and Ceballos-Barbancho, A., 2012. The contrasted evolution of high and low flows and precipitation indices in the Duero basin (Spain). Hydrological Sciences Journal, 57 (4), 591–611.  相似文献