Classification of Vertical Wind Speed Profiles Observed Above a Sloping Forest at Nighttime Using the Bulk Richardson Number

Wind speed profiles above a forest canopy relate to scalar exchange between the forest canopy and the atmosphere. Many studies have reported that vertical wind speed profiles above a relatively flat forest can be classified by a stability index developed assuming wind flow above a flat plane. However, can such a stability index be used to classify vertical wind speed profiles observed above a sloping forest at nighttime, where drainage flow often occurs? This paper examines the use of the bulk Richardson number to classify wind speed profiles observed above a sloping forest at nighttime. Wind speed profiles above a sloping forest were classified by the bulk Richardson number Ri _B . Use of Ri _B distinguished between drainage flow, shear flow, and transitional flow from drainage flow to shear flow. These results suggest that Ri _B is useful to interpret nighttime CO₂ and energy fluxes above a sloping forest. Through clear observational evidence, we also show that the reference height should be high enough to avoid drainage-flow effects when calculating Ri _B .     

A global river routing network for use in hydrological modeling

In this paper a relatively simple procedure is presented to construct a global river routing network on a 0.5° latitude–longitude grid. In this network all grid cells in a catchment are coupled and have a flow direction, making it a useful tool in the modeling of river flow on a global scale. The flow directions are based on a digital elevation model and on information on the locations of major rivers (‘stream burning’). The presented river routing network is specifically designed for the assessment of fresh water shortages. We tested the validity of the river routing network by comparing the computed drainage areas with published estimates. This comparison revealed a good similarity and it is concluded that the presented river routing network has sufficient quality to be implemented in global climate models. This could mean a considerable improvement of the surface parameterization in these models.     

Orientation of a pad of SAGD well pairs in an Athabasca point bar deposit affects performance

It has been shown that the performance of a Steam-Assisted Gravity Drainage (SAGD) well pair is affected by its orientation and position within a point bar deposit. In typical commercial operations, multiple horizontal wellpairs, usually arranged parallel to each other, are arranged in pads within oil sands reservoirs. Thus, the overall performance of the recovery process in a point bar is not represented by a single well pair but how the set of well pairs interact with the structure and geometry of the point bar notably including the arrangement of inclined heterolithic strata relative to the SAGD well pairs. This research describes how the point bar structure impacts the performance of a pad of SAGD wellpairs and the impact of pad orientation on performance of the pad. Also, the results show that the variability of the performance of the well pairs within the pad is large and thus, single well pair models do not provide sufficient analysis of the SAGD process performance due to the heterogeneity of the point bar. In other words, pad-scale models are required for recovery process evaluation and design. Furthermore, the variability of performance obtained from the models provides an estimate of the variability that may result for systems where seismic data is not available or is not sufficient to fully characterize the point bar.     

Types and Causes of Debris Flow Damage to Drainage Channels in the Wenchuan Earthquake Area

Debris flows are among the most common geological disasters in China,and have been particularly frequent in Sichuan Province since the Wenchuan earthquake on 12 May 2008.The construction of debris flow drainage channels is a countermeasure used to distribute debris flow fans,and these channels play a critical role in the mitigation and prevention of damage resulting from debris flows.Under field conditions,the useful life of drainage channels can be greatly shortened as a result of strong abrasions to the drainage structure caused by the debris flow.Field investigations have shown that the types of damage to drainage channels include（a） erosion caused by hyper-concentrated silt flow,（b） impact fractures and foundation scour at the groundsills of the drainage channel,（c） destruction of the drainage channel outlet,and（d） destruction of the drainage channel caused by debris flow abrasion.In addition,based on the destruction of the drainage channel during the debris flow drainage process,a new type of drainage channel with energy dissipation components was proposed and applied in a steep,narrow gully for debris flow mitigation.Moreover,design and engineering repair recommendations for drainage channels are provided as a reference for repairing the damage to the channel.The results can provide an important reference for the effective repair and optimal design of drainage channels.     

考虑碎石桩排水能力复合地基中孔压长消解析解

由于地震作用时间较短,且碎石桩渗透能力和土体渗透能力相比并不是无限大,因此本文考虑碎石桩排水能力研究了碎石桩桩体材料由地震引起的孔压的长消规律。根据比奥固结理论综合考虑碎石桩的排水能力和相应的初始条件及边界条件,推导出了能够真实反映碎石桩排水减压作用在地震期超孔隙水压力产生、扩散、消散过程中的贡献作用的一般解析解公式。同时讨论了碎石桩渗透能力的不同对抗震液化的影响作用。     

乌江流域水库沉积物中生物硅的测定方法及其环境意义

采用碱提取法中的单点法与多点法相结合,测定了乌江流域水库沉积物中生物硅的含量,并对多点提取法进行了改良。采用多个离心管分装定量样品进行连续振荡,每小时提取1个样品进行测定。对多个时间点的提取结果,利用线性回归法分析得出最佳提取时间,优化最佳提取液,然后利用单点提取-硅钼蓝检测法测定沉积物中生物硅的含量。该方法既保证了单点法的快速,也减小了多点法的多次提取操作与提取时的体积误差。本文根据测定结果探讨了乌江流域水库沉积物中生物硅含量变化规律及其环境意义。     

Development and morphometry of drainage network in volcanic terrain, Central Anatolia, Turkey

This paper presents the results of morphotectonic and morphometric research carried out in order to determine the neotectonic development of the volcanic mountains and a drainage network in SW Cappadocia. The study area extends among the Aksaray, Ni?de, and Nev?ehir Provinces. The study area comprises Hasanda?, Melendiz, Keçiboyduran, Göllüda? Mountains and the adjacent parts of these volcanic mountains.Data collected exclusively from 1:25,000 digitised topographic maps and 10 m-resolution DEMs were used to define parameters related to the longitudinal profile of streams. The study area was divided into 10 volcanic units. Longitudinal profiles of 20 streams and stream orders were analysed to determine a regional tectonic differentiation pattern in these units. The streams in the study area drain into four different tectonic depressions. These depressions are Aksaray plain controlled by the Tuz Gölü fault (TGF), Çiftlik plain controlled by the Keçiboyduran–Melendiz fault (KMF), Misli plain controlled by the Derinkuyu fault (DF), and Bor plain controlled by the Ni?de Fault Zone (NFZ). An analysis of morphometric parameters shows that the development of a drainage network is associated with faults and rock resistance. Occurrence of morphometric parameters with different values in units reveals that the volcanic mountains were not uplifted in the same period and were subjected to different morphologic processes. High total order number in the south of Hasanda? (unit 3) and Melendiz Mountains (unit 7) indicate that the uplift ratio of the southern part is much greater than that of the northern part. Moreover, development of the drainage network in the south is in a more advanced phase than in the north. Indeed, the drainage network in the north is in the youngest erosional phase of all parts of the study area. The increased stream length-gradient indices (SL), and stream gradients and an analysis of headward erosion show that the streams displaying the longest and highest reach of the erosional phase are all in the southern part of Keçiboyduran and Melendiz Mountains. The longitudinal profile (Lp) of the present thalweg of the streams is irregular. The irregular Lp are associated with four different causes. These are geological variations in resistance, tectonics, and volcanic topography and downcutting in response to stream incision. The beginning of the fluvial incision in the northern part is younger than in the south.     

Fractal measures of drainage network to investigate surface deformation from remote sensing data: A paradigm from Hindukush (NE-Afghanistan)

This approach represents the relative susceptibility of the topography of the earth to active deformation by means of geometrical distinctiveness of the river networks. This investigation employs the fractal analysis of drainage system extracted from ASTER Global Digital Elevation Model (GDEM-30m resolution). The objective is to mark active structures and to pinpoint the areas robustly influenced by neotectonics. This approach was examined in the Hindukush, NE-Afghanistan. This region is frequently affected by deadly earthquakes and the modern fault activities and deformation are driven by the collision between the northward-moving Indian subcontinent and Eurasia. This attempt is based on the fact that drainage system is strained to linearize due to neotectonic deformation. Hence, the low fractal dimensions of the Kabul, Panjsher, Laghman, Andarab, Alingar and Kocha Rivers are credited to active tectonics. A comprehensive textural examination is conducted to probe the linearization, heterogeneity and connectivity of the drainage patterns. The aspects for these natural textures are computed by using the fractal dimension (FD), lacunarity (LA) and succolarity (SA) approach. All these methods are naturally interrelated, i.e. objects with similar FD can be further differentiated with LA and/or SA analysis. The maps of FD, LA and SA values are generated by using a sliding window of 50 arc seconds by 50 arc seconds (50" × 50"). Afterwards, the maps are interpreted in terms of regional susceptibility to neotectonics. This method is useful to pinpoint numerous zones where the drainage system is highly controlled by Hindukush active structures. In the North-Northeast of the Kabul block, we recognized active tectonic blocks. The region comprising, Kabul, Panjsher, Andrab, Alingar and Badakhshan is more susceptible to damaging events. This investigation concludes that the fractal analysis of the river networks is a bonus tool to localize areas vulnerable to deadly incidents influencing the Earth’s topography and consequently intimidate human lives.     

Automated suitable drainage network extraction from digital elevation models in Taiwan's upstream watersheds

Automatically extracting drainage networks from digital elevation models coupled with the constant stream threshold value is a regular method. These extracted networks can be verified by comparing the channel initiation points with those from real networks. From the results analysed, the differences in channel initiation points will affect the network geometries, geomorphological indices and hydrological responses. This paper develops two automatic algorithms, the headwater‐tracing method and the fitness index, to trace the flow paths from headwaters to the outlet and to calculate the reasonable stream threshold. Instead of the method determined by trial and error or field survey, the accurate channel initiation points can be obtained from airborne photographs coupled with high‐resolution SPOT images for suitable drainage network extraction. Copyright © 2005 John Wiley & Sons, Ltd.     

Channel network extent in the context of historical land use,flow generation processes,and landscape evolution in the North Carolina Piedmont

Intensive agricultural land use in the 18th to early 20th centuries on the southeastern Piedmont resulted in substantial soil erosion and gully development. Today, many historically farmed areas have been abandoned and afforested, and such landscapes are an opportunity to study channel network recovery from disturbance by gullying. Channel initiation mapping, watershed area–slope relationships, and field monitoring of flow generation processes are used to identify channel network extent and place it in hydrologic, historical and landscape evolution context. In six study areas in the North Carolina Piedmont, 100 channel heads were mapped in fully‐forested watersheds, revealing a channel initiation relationship of 380 = AS^1.27, where A is contributing area (m²) and S is local slope (m/m). Flow in these channels is generated by subsurface and overland flow. The measured relative slope exponent is lower than expected based on literature values of ~2 for forested watersheds with subsurface and overland flow, suggesting that the channel network extent may reflect a former hydrological regime. However, geomorphic evidence of recovery in channel heads within fully forested watersheds is greater than those with present day pasture. Present day channel heads lie within hollows or downslope of unchanneled valleys, which may be remnants of historical gullies, and area–slope relationships provide evidence of colluvial aggradation within the valleys. Channel network extent appears to be sensitive to land use change, with recovery beginning within decades of afforestation. Channel initiation mapping and area–slope relationships are shown to be useful tools for interpreting geomorphic effects of land use change. Copyright © 2012 John Wiley & Sons, Ltd.