Post‐wildfire changes in suspended sediment rating curves: Sabino Canyon,Arizona

Wildfire has been shown to increase erosion by several orders of magnitude, but knowledge regarding short‐term variations in post‐fire sediment transport processes has been lacking. We present a detailed analysis of the immediate post‐fire sediment dynamics in a semi‐arid basin in the southwestern USA based on suspended sediment rating curves. During June and July 2003, the Aspen Fire in the Coronado National Forest of southern Arizona burned an area of 343 km². Surface water samples were collected in an affected watershed using an event‐based sampling strategy. Sediment rating parameters were determined for individual storm events during the first 18 months after the fire. The highest sediment concentrations were observed immediately after the fire. Through the two subsequent monsoon seasons there was a progressive change in rating parameters related to the preferential removal of fine to coarse sediment. During the corresponding winter seasons, there was a lower supply of sediment from the hillslopes, resulting in a time‐invariant set of sediment rating parameters. A sediment mass‐balance model corroborated the physical interpretations. The temporal variability in the sediment rating parameters demonstrates the importance of storm‐based sampling in areas with intense monsoon activity to characterize post‐fire sediment transport accurately. In particular, recovery of rating parameters depends on the number of high‐intensity rainstorms. These findings can be used to constrain rapid assessment fire‐response models for planning mitigation activities. Copyright © 2006 John Wiley & Sons, Ltd.     

Yield design of dry‐stone masonry retaining structures—Comparisons with analytical,numerical, and experimental data

Over the past few years, there has been a steady increase in the interest in dry‐stone walling not only to preserve existing constructions but also to build new ones. Yet, dry masonry's expansion is slowed down by the lack of scientific knowledge to assess its reliability. This study aims at contributing to the construction of this scientific frame using a simplified model based on yield design and homogenization, which can be directly exploited for engineering purposes. A new analytical expression of the ultimate load is thus established. Then, the validity of the method is assessed by comparisons with limit equilibrium analysis, distinct element method, and field trials. Finally, possible improvements of the model are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

中国生态农业地质研究及其前景

中国29个省、市、自治区的土壤质量和农作物优质高产与土壤环境中化学元素N、P、K、S、Fe、Mn、Cu、Zn、B、Mo、V、Sr、Ti、Mg、La、Ce、Pr、Nd、Sm、Eu、Y、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Ca、Co、Ni、F、Tl、Si、Na、Cr、Ph、Cd、Hg、Se、Ba、Te、Ta及有机质、酸碱度、含盐量有密切的关系。土壤的质量为优质高产打下了基础,应充分地开发利用和保护。提出了生态农业地质研究的目的、内容、方法、管理及其前景。     

Groundwater potentiality index: a strategically conceived tool for water research in fractured aquifers

Durable development requires full profit and knowledge of natural resources potentialities. Multi-criterion approaches that encompass geological, morphological, hydrological and Geographical Information System technologies are ones of exiting developments in environmental sciences. This work is a proposition of a numerical model based on a groundwater potentiality index (GPI) calculation, using data on rock fracturing, lithology, drainage, topography, rainfall and drilling water yield. It provides the ability to identify areas indicating favorable conditions for exploratory well positioning in semi-arid zones with non-permeable outcrops. It is therefore a helpful tool to assist water resources prospecting in deprived regions. The newly conceived approach has been applied in the southeastern boundary of the Bouregreg and coastal basins of Central Morocco, where Paleozoic fractured rocks outcrop. The suitability of the GPI method use was verified by comparing the GPI map values with water yield of thirteen pumping tests in a field checking area, which revealed promising results.     

银川平原土壤盐渍化与中低产田遥感应用研究

土壤盐渍化是影响农业生产与生态环境的一个重要因素。长期以来,宁夏银川平原的次生土壤盐渍化问题十分突出,形成了许多盐渍型中低产田,影响和制约了区域农业的可持续发展。主要采用遥感解译方法提取了银川平原土壤盐渍化的分类与分布的现状信息。在此基础上,依据中低产田的分类标准,将相关的耕地类型、土壤肥力、作物产量、灌排水指标等因子转化成数字化专题图层,采用多源信息复合分类的方法,通过“综合分析,主导因子判定”实现了GIS辅助下的中低产田分类,为遥感和地理信息系统技术在土壤盐渍化和中低产田调查研究中的应用,探索出了一条可行的途径。     

安阳夏玉米生长期气候要素与产量的灰色关联分析

采用灰色关联度分析了安阳夏玉米生育期间主要气象要素与夏玉米产量的关系，明确了当地夏玉米产量在年度间的差异主要以积温为主导因素，不同生育期中的气候因素以拔节-乳熟期的光照和降水量对产量影响最大，而乳熟-成熟的降水量对产量的影响程度最弱。     

A comparative analysis of three habitat suitability models for commercial yield estimation of Tapes philippinarum in a North Adriatic coastal lagoon (Sacca di Goro, Italy)

Habitat Suitability (HS) models have been extensively used by conservation planners to estimate the spatial distribution of threatened species and of species of commercial interest. In this work we compare three HS models for the estimation of commercial yield potential and the identification of suitable sites for Tapes philippinarum rearing in the Sacca di Goro lagoon (Italy) on the basis of six environmental factors. The habitat suitability index (HSI) is based on expert opinion while the habitat suitability conditional (HSC) is calibrated on observational data. The habitat suitability mixed (HSM) model is a two-part model combining expert knowledge and regression analysis: the first component of the model uses logistic regression to identify the areas in which clams are likely to be present; the second part applies the same parameter-specific suitability functions of the HSI model only in the areas previously identified as productive by the logistic component.The HS models were validated on an independent data set and estimates of potential yield of the Goro lagoon were compared. The effectiveness of the three approaches is then discussed in terms of predicted yield and identification of suitable sites for farming.     

Compressibility behaviour of lime-stabilized clay

Lime stabilization reactions result in the formation of inter-particle cementation bonds that improves strength and reduce compressibility of clay soils. Though several studies in the past have focused on the impact of lime stabilization on the strength behaviour, few studies have examined the impact of lime stabilization on the compressibility behaviour of clay soils. The present study examines the compressibility behaviour of lime-stabilized soils in light of the frameworks proposed for saturated cemented clays. Cementation bonds formed during the lime stabilization reactions imparted yield stress in the range of 3900–5200 kPa to the artificially cemented specimens. The compression behaviour of these artificially cemented specimens in the pre-yield stress and post-yield stress regions conformed to the framework proposed for saturated cemented soils.     

Applicability and methodology of determining sustainable yield in groundwater systems

There is currently a need for a review of the definition and methodology of determining sustainable yield. The reasons are: (1) current definitions and concepts are ambiguous and non-physically based so cannot be used for quantitative application, (2) there is a need to eliminate varying interpretations and misinterpretations and provide a sound basis for application, (3) the notion that all groundwater systems either are or can be made to be sustainable is invalid, (4) often there are an excessive number of factors bound up in the definition that are not easily quantifiable, (5) there is often confusion between production facility optimal yield and basin sustainable yield, (6) in many semi-arid and arid environments groundwater systems cannot be sensibly developed using a sustained yield policy particularly where ecological constraints are applied. Derivation of sustainable yield using conservation of mass principles leads to expressions for basin sustainable, partial (non-sustainable) mining and total (non-sustainable) mining yields that can be readily determined using numerical modelling methods and selected on the basis of applied constraints. For some cases there has to be recognition that the groundwater resource is not renewable and its use cannot therefore be sustainable. In these cases, its destiny should be the best equitable use.

Numerical simulation of debris flow with application on hazard area mapping

A numerical program developed for field application is presented in this paper. We use the generalized Julien and Lan [8] rheological model to simulate debris flows. Due to the derivative discontinuous nature of the constitutive law, flow is separated into plug region and bottom region (with stress greater than yield stress). The program solves the plug flow layer solution first, and then corrects the solution with the bottom layer approximation. Numerical scheme with upwind method and central difference in space and Adam–Bashforth third-order scheme in time is used for both layers. The scheme is tested against analytical solutions and laboratory experiments with very good results. Application to a field case with more complicated geometry also achieves good agreement, with error less than 5% compared to field measurements. The final example demonstrates how this numerical program is used in a preliminary design.