以位于秦岭山地的陕西佛坪县城为研究对象,对其泥石流灾害及其防治状况进行研究.研究采用地质灾害防治方法,通过野外考察,即对各条沟泥石流的形成机理、运动和致灾方式等搜集了大量第一手资料,并结合室内分析整理,提出防治措施.认为在实施中应以防为主,防治结合,根据泥石流形成条件、运动规律,致灾方式等因地制宜,因害设防,并结合水土流失治理,改变生态环境,控制泥石流发展.防治中应以工程防治为主,进而达到综合治理,工程措施应在泥石流沟的形成区采取拦档措施,堆积区采用排泄措施,即上栏下排的工程治理,这样才能做到防患于未然.

•Improved understanding of overland flow generation mechanism.•New method for modeling microtopography-dominated, discontinuous overland flow.•Unique cell-to-cell (C2C) and puddle-to-puddle (P2P) two-domain modeling.•Hierarchical modeling of P2P filling–spilling–merging–splitting dynamics.

探讨济阳拗陷临南—钱官屯地区化探异常成因机制.通过对临南—钱官屯地区不同构造单元油井和干井中酸解烃特征和微渗漏方式的研究,结合石油地质条件,从油气成藏的角度分析烃类运移、聚集及其微渗漏散失的全过程.结果表明研究区北部地层中以扩散为主,南部以渗透为主或者不存在微渗满效应,揭示渗漏源和盖层条件是烃类微渗满的主控因素.临南—钱官屯地区近地表化探异常模式为“渗漏源影响下的断控异常模式”,钱斜14井以北盖层条件和渗漏源条件都最优越,是研究区内最有利的勘探区.

Surface microtopography affects infiltration and soil-water flow (both magnitude and direction). The objective of this study is to evaluate the final distribution of wetting front under the influence of surface microtopography. Laboratory-scale infiltration and unsaturated flow experiments were conducted for various microtopographic surfaces and boundary conditions. In addition, twoand three-dimensional numerical modeling was conducted using the HYDRUS software. The simulated wetting front distributions were compared. The results from this combined experimental and modeling study indicated that surface microtopography had strong influences on soil water movement. A uniformly distributed wetting front was eventually achieved although soil surfaces had dissimilar topographic characteristics. However, the timing to reach the uniform flat wetting front varied, depending on surface microtopography, soil hydraulic properties, and boundary conditions.

Surface microtopography affects overland flow, infiltration, soil erosion, pollutant transport, and other fundamental hydrologic and environmental processes across scales. Under the influence of surface depressions, overland flow essentially features a series of progressive puddle-to-puddle (P2P) filling, spilling, merging, and splitting processes. The objectives of this study are to characterize puddles and their hierarchical relationships and model the microtopography-controlled P2P processes. We proposed a new modeling framework for simulating the P2P overland flow dynamics through cell-to-cell (C2C) and P2P routing for a set of puddle-based units (PBUs) in a well-delineated, cascaded P2P drainage system. Testing of the P2P model demonstrated its potential to improve overland flow modeling and hydrologic connectivity analysis by explicitly incorporating the hydrologic roles of depressions and quantifying the real microtopography-controlled P2P dynamics.

Surface digital elevation model (DEM) resolution receives increasing attention because of its importance in topographic analysis (e.g.,quantification of surface depressions) and hydrologic modeling. Varied and even contrary conclusions have been obtained concerning the effects of DEM grid size on surface depression properties. Land surfaces are featured with a number of microtopography-controlled, localized areas, and their connections may significantly alter hydrologic and geomorphologic processes. Few efforts have been made to examine the effects of DEM resolution on surface depression properties and hydrologic connectivity. This study aimed to evaluate such resolution effects by two dimensionless parameters: the DEM representation scale (the ratio of DEM grid size to correlation length, representing horizontal resolution) and the surface roughness scale (the ratio of random roughness to correlation length, representing vertical topographic variability). A puddle delineation program was utilized to quantify depression properties for a variety of topographic surfaces characterized by different DEM resolutions, including small-scale surfaces with random roughness, field plots, and watershed surfaces. In particular, a puddle-to-puddle (P2P) conceptual model was used for hydrologic connectivity analysis. It was found that puddle properties depended on both dimensionless and . The significantly influenced the calculations of structural and functional hydrologic connectivity. Using DEMs with a coarser resolution or higher tended to overestimate hydrologic connectivity and simplified hydrograph for a surface with numerous small-scale depressions. The DEM resolution or dimensionless had significant influences on the development of functional hydrologic connectivity, especially at the early stage of the rainfall-runoff process. (C) 2013 American Society of Civil Engineers.

Land surfaces are generally not smooth and show certain irregularity. Overland flow on such surfaces is essentially discontinuous and exhibits strong variability and complexity. Modeling of the spatio-temporal variability and heterogeneity of overland flow and the hydrotopographic effects has been proven to be a challenge. The objective of this study is to quantitatively describe the intrinsic spatio-temporal variations in hydrologic connectivity associated with overland flow generation. Firstly, a puddle-to-puddle (P2P) hydrologic connectivity concept was proposed to characterize runoff generation processes and the related spatio-temporal dynamics. Secondly, a laboratory overland flow experiment was conducted to characterize the dynamic puddle filling and spilling processes, hydrologic connectivity, and outlet discharge. Thirdly, a conceptual P2P model was applied to simulate the P2P overland flow dynamics, calculate flow discharge, and track the evolution of hydrologically connected areas. Particularly, two modified hydrologic connectivity indices, time-varying connectivity function and connectivity length, were proposed to characterize the properties and dynamic changes in hydrologic connectivity. Furthermore, the influences of surface topography, rainfall, and surface slope on hydrologic connectivity were evaluated. The proposed hydrologic connectivity indices effectively revealed the variability and the threshold behavior of overland flow generation. It was demonstrated that the dynamic P2P processes governed hydrologic connectivity, controlled surface runoff generation, and altered the flow drainage patterns. Temporal variations of rainfall intensity changed the occurrence timing of the P2P dynamics and evolution of connected areas, while spatial variations of rainfall intensity directly influenced the overall development of hydrologic connectivity of a hydrologic system. Surface slope showed considerable influences on hydrologic connectivity. The results suggested that critical slope(s) could exist, at which a sharp change in flow drainage area and hydrologic connectivity occurred. (C) 2013 Elsevier B.V. All rights reserved.

Land surface is generally not smooth. The existence of puddles breaks the continuity of various hydrologic features/properties. The spatial connectivity of topographic surfaces has significant influence on a series of hydrologic and geomorphologic processes and results in localized and independent hydrologic mass balance. This study centers on examining the effects of surface microtopography on hydrologic connectivity. An instantaneous-profile laser scanner is utilized to acquire highresolution DEMs of surfaces with varying microtopographic characteristics. A puddle delineation software package is used to delineate the surfaces and quantify the relationships of puddles. Particularly, both structural and functional hydrologic connectivity properties are examined. In addition, the effects of DEM resolutions on hydrologic connectivity are investigated. It is found that the approach of spatial mapping of the connected areas is capable of describing the spatial complexity of connectivity of topographic surfaces. The surfaces of different microtopographic features have unique changing patterns of normalized discharge, which provides promising information to better understand the related hydrologic processes.

Surface runoff and infiltration are two essential hydrologic processes. Microtopography is one of the key factors affecting these processes. Thus, quantification of surface microtopography is critical to hydrologic modeling. In this study, high-resolution digital elevation models (DEMs) were acquired by using an instantaneous-profile laser scanner. In addition, some hypothetical surfaces were created. Six soil surfaces with different roughness were selected and three data processing methods were used in the computation of random roughness (RR) index for characterizing surface microtopography. Varying sloping surfaces were created by rotating the original ones and a coordinate conversion program was used to generate new corresponding DEM data. Maximum depression storage (MDS) was estimated by using two RR index-based methods. Particularly, a puddle delineation (PD) program was also applied to precisely compute the MDS for each surface and the results were compared with those from the RR index-based methods. Finally, the performance and applicability of the three RR index-based methods were evaluated and some improvements were suggested.

Surface microtopography is one of the key factors that control overland flow generation, surface runoff, and infiltration processes. Surface slope tends to change the characteristics of individual puddles and their hydrologic properties. To evaluate the slope effects on surface depressions, four rough surfaces characterized by various scale depressions and peaks and a series of rotated sloping surfaces were created. An instantaneous-profile laser scanner was used to obtain high-resolution DEM data. A puddle delineation program was used to calculate the maximum depression storage (MDS) and maximum ponding area (MPA). Furthermore, a coordinate conversion program was developed and used to transform the coordinate system, generate varying sloping surfaces, and create new DEMs. The DEMs of the new sloping surfaces generated by the coordinate conversion program were compared with the actual ones, and good agreement was achieved. Critical slopes corresponding to significant changes in hydrologic/hydraulic properties were identified. Although MDS and MPA normally decreased with an increase in slope, an increasing pattern was also observed. For the relationship between contributing area (CA) and surface slope, a stepwise increasing pattern was observed.

Digital elevation models (DEMs) are commonly utilized for characterizing surface topography in watershed modeling. More often, DEMs can be the sole information that is used for watershed delineation, determination of flow directions and accumulations, and identification of subbasin boundaries. Thus, the resolution or grid size of the DEM data is critical. Surface depression storage is one of the primary topographic attributes and an essential hydrologic variable in watershed hydrologic modeling. Efforts have been made to evaluate the effects of grid spacing of DEMs on topographic attributes and hydrologic analyses. However, previous studies showed varied relationships between grid spacing and surface depression storage. The objective of this study is to quantitatively evaluate the effects of DEM resolutions on the computed maximum depression storage (MDS) and maximum ponding area (MPA). Six surfaces that possess varying spatial scales and microtopographic features are used in the discussion. In addition, six interpolation methods are selected and their influences on MDS also are evaluated. It is found from this in-depth study that grid pacing of DEMs affects MDS and MPA differently, depending on the characteristics of surfaces, delineation methods, and interpolation approaches used for generating the DEM data for various spatial scales.

Surface microtopography plays an important role in overland flow generation and soil erosion processes. Characterization of surface depressions and delineation of the entire watershed are critical to watershed modeling and management. In most hydrologic models, however, surface depression storage is estimated indirectly and inputted as a known value. In addition, it is often assumed that overland flow initiates after all surface depressions are fully filled. In reality, surface microtopography may control overland flow generation, surface runoff, soil erosion, and other hydrologic processes in a dynamic manner. The role of depressions that have various spatial scales and distribution characteristics is far beyond the functions of storing and detaining/retaining surface runoff. In this study, an improved surface delineation method was proposed to identify surface depressions and their relationships, precisely quantify the surface microtopography, and compute the maximum depression storage based on high-resolution DEM data obtained by using an instantaneous-profile laser scanner. Furthermore, a user-friendly, Windows-based software package was developed to facilitate the associated computations and visualization. The delineation method and the related software were tested using various scale DEM data. It is demonstrated that the new delineation approach is effective and efficient.

Not all transactions care about repeatable reads. They are willing to forego problems arising with phantoms. We’ll call this level “nonrepeatable reads”. (This is called degree 2 isolation also called cursor stability (CS)). CS differs from RR in that read locks are discarded once a tuple has been read. Write locks on tuples, like RR, are held to the end of the transaction. Note that CS executions are not truely serializable (because of the nonrepeatability of reads).