Simple I/O-efficient flow accumulation on grid terrains

The flow accumulation problem for grid terrains takes as input a matrix of flow directions, that specifies for each cell of the grid to which of its eight neighbours any incoming water would flow. The problem is to compute, for each cell c, from how many cells of the terrain water would reach c. We show that this problem can be solved in O(scan(N)) I/Os for a terrain of N cells. Taking constant factors in the I/O-efficiency into account, our algorithm may be an order of magnitude faster than the previously known algorithm that is based on time-forward processing and needs O(sort(N)) I/Os.Comment: This paper is an exact copy of the paper that appeared in the abstract collection of the Workshop on Massive Data Algorithms, Aarhus, 200

Application of Geo-Spatial Technology in Identifying Areas Vulnerable to Flooding in Ibadan Metropolis

This study makes use of the integrated approach of Remote Sensing and GIS techniques in flood management with the goal of identifying areas vulnerable to flood hazard in Ibadan Metropolis. Ibadan is the largest indigenous city in the continent of Africa and had experienced a lot of various severities of flood occurrences in the last fifty years. Topographic Map and Landsat TM image of 1993 and 2000 respectively were processed, scanned, digitized, interpolated, classified and overlaid using ILWIS 3.3 academic and ARC GIS 9.2 software modules to generate classified land cover map, Digital Terrain Map (DTM), Triangulated Irregular Network (TIN) and flood vulnerability map of the study area respectively. The results obtained shows that, areas lying along the banks of River Ona and River Ogunpa are most vulnerable to flood hazards with the vulnerability decreasing towards the northern part of the city, much of the area is built up with improper planning and this gives rise to high vulnerability to flash flood hazards. The Odo Ona, Idi Isin, Eleyele, Olopometa and Molete areas are the most vulnerable to flood threat. The incessant violation of land use plan, unchecked population growth, old nature of the structures and poor materials used in the construction of the houses make the areas vulnerable to flood hazard. In reducing the vulnerability of these areas from flood there is need for improved land use planning, removal of structures from River Ona and Ogunpa flood plains around the city, intensify environmental education to the residents and enhance the active participation of government agencies in the continual generation of flood vulnerability maps of urban centres. Keywords: Flood, Vulnerability, DEM, GIS, Remote Sensing, TIN

Ice-Cover and Jamming Effects on Inline Structures and Upstream Water Levels

River ice cover is a reoccurring phenomenon in the Northern United States every year. Sheets and layers of ice result in a rise of water surface elevation and may lead to ice jams in a river. This research explains the modeling of a river reach through Northern Illinois containing a structural weir and how the water profile is effected during ice cover and ice jam events. The Hydraulic Engineering Center’s River Analysis System was used in conjunction with Esri ArcMap software to model a portion of the river for analysis. The study area of the Rock River flowing through Oregon, IL is known to freeze and ice over during the winter months in Northern Illinois. Data from the United States Geological Survey and National Oceanic and Atmospheric Administration were utilized to obtain cross-section and discharge measurements. The impacts of an ice jam occurring upstream of the weir and downstream of the weir were studied. The effects of the ice jam on the upstream water levels were also evaluated to observe if any flooding may occur inside the town or even farther upstream. Results of the ice cover and ice jam data were then compared to those of the Rock River under normal open flow conditions thus observing the change in water level, Froude number, and flow velocity. Results from this study help to point out the significance of ice jam occurrences and their effects on inline structures and future flooding concerns in the surrounding area

Agricultural Assessment: Pecan Orchard Feasibility Study

East Texas has predominantly been categorized historically as a forestry and timber management region. The nearest region to expectedly encounter viewing a large number of properties containing the growth of nut-bearing tree plantations, better known as orchards, is the Hill Country or South Texas Regions. During 2012, I witnessed a rural real estate transaction between an East Texas timber landowner and successful almond orchard farmer. The almond farmer had no previous experience with the practice and management of Texas loblolly pine plantations; however, he had interest in diversifying his real estate investment portfolio to include a pine plantation offering a different soil type than he was used to cultivating for his almond farms. The more than two-thousand acre Neches River property of his choice, was in fact a practical timberland investment, with a desirable projected return-on-investment. As a result, the almond farmer can now learn the principles associated with growing, managing, and harvesting pine timber in East Texas, in addition to examining the new soil type and preparing it for his experimental East Texas almond orchard farm. Due to the almond farmers unorthodox endeavor, the experience enlightened me and generated the basis of the following study; does the East Texas region host lands that are practical, or even potentially possible, to develop large acreage into nut-bearing orchards

Estimation Of Time Of Concentration Using Triangulated Irregular Network Method

In Malaysia, Manual Saliran Mesra Alam (MSMA) has proposed two calculation methods to obtain areas between the isochrones that have been widely practiced at the moment. They are Grid method and Conventional method. However, these methods pose certain problems of their own. Although the Grid method is more detail and accurate when compared to the Conventional method, but that is extremely tedious and time consuming. Conventional method on the other hand is simpler to use. But, the results are not consistent. The results are very subjective because it depends on each user’s experience and judgement. Therefore, a new calculation method named Triangulated Irregular Network (TIN) method has been designed and developed in this research to improve the Time-Area method calculation. This method is computer based and thus the algorithm of TIN method was developed. The algorithm of the TIN method is explained in this research. A study site was constructed and eight sets of rainfall data were collected. All the results from each calculation method were verified with the collected site data to compare their accuracy. Investigation upon their efficiency and reliability were also presented in this research. The comparison showed that TIN method has higher accuracy. In the correlation coefficient comparison among the methods, TIN method has average accuracy of 0.988, Grid method has average accuracy of 0.936 and Conventional method has average accuracy of 0.948. When calculating their difference against the observed data in percentage, TIN method has average difference of 14.29%, Grid method has average difference of 25.67% and Conventional method has average difference of 24.52%. When using the peak flow comparison for the difference against the observed data, the results shows that TIN method has average difference of 3.48%, Grid method has average difference of 5.88% and Conventional method has average difference of 7.72%. Lastly, the methods were compared using the total flow volume. It was demonstrated that the TIN method has different of 0.19%, Grid method has different of 0.43% and Conventional method has different of 4.80% when compared to the observed data. The TIN method has the highest accuracy and reliability among the three methods. Besides, this research also showed that the newly developed TIN method algorithm is easier to use, less time consuming and more reliable

Mobile Augmented Reality for Flood Visualisation in Urban Riverside Landscapes

Frequency of flooding events worldwide has increased significantly over the past decades, and with it so has the need to raise citizen’s awareness of potential dangers within local flood zones. Smart phones provide a feasible means with which to educate the public in this way. We present a working smart phone app to engage the public with local flood zones by visualising potential flood levels. An interactive augmented reality (AR) tool provides in situ modeling of simple prototype 3D building models (cuboids) along a riverside, which are used to “occlude” an augmented flood plane within the scene. Flood plane height may be adjusted by the user. We discuss related AR work, tools for real-time in situ geometry modeling, app operation and present and on site demonstration

Automated Classification of Airborne Laser Scanning Point Clouds

Making sense of the physical world has always been at the core of mapping. Up until recently, this has always dependent on using the human eye. Using airborne lasers, it has become possible to quickly "see" more of the world in many more dimensions. The resulting enormous point clouds serve as data sources for applications far beyond the original mapping purposes ranging from flooding protection and forestry to threat mitigation. In order to process these large quantities of data, novel methods are required. In this contribution, we develop models to automatically classify ground cover and soil types. Using the logic of machine learning, we critically review the advantages of supervised and unsupervised methods. Focusing on decision trees, we improve accuracy by including beam vector components and using a genetic algorithm. We find that our approach delivers consistently high quality classifications, surpassing classical methods

Application of GIS in Water Management of Eleyele Catchment, South-Western Nigeria

Eleyele dam has drastically reduced in capacity since its inception in 1942. There are frequent flood incidences within the dam catchment area- noteworthy of them is the August, 2011 flood incidence. This research studies the hydrological condition of Eleyele catchment through the use of Geographic Information System. The topographical maps, digital elevation measurement maps (DEM) and hydrological maps of the Eleyele catchment were produced through GIS watershed delineation process for the year 1967 and year 2014.The results show that there is an average lowering of elevation of about 14.63m within the catchment which has greatly affected the hydrological pattern of the catchment. The Triangulated Irregular Network (TIN) of the catchment was used to produce flood risk map. The map showed that 25.24% of the catchment is prone to flooding. The study showed that there is a change in topography of Eleyele Catchment within the period studied. This is due to the urbanization of the area. Keywords: Eleyele Dam, Flood Incidences, Hydrological Condition, GIS, Watershed Delineation Process, Triangulated Irregular Networ