Arghavanian, Azar
Efficient management of water resources is of great importance regarding ever increasing population and water droughts related to climate change. Drainage networks are important geomorphologic and hydrologic features which significantly control runoff generation. Recently, it has been feasible to monitor the earth’s surface and natural phenomena with the aid of remote sensing techniques. However, very high spatial resolution is needed for monitoring small waterways and knowledge of accurate drainage patterns is very important for correct modelling of hydrology. LiDAR (Light Detection and Ranging), which is an active remote sensing technique, uses near-infrared laser light to measure the distance from the sensor to a target on the earth’s surface. LiDAR data can be used in many scientific fields including topographic mapping, hydrology and land cover classification. This thesis explores the applicability of high-posting-density LiDAR data for terrain mapping with a focus on automated detection of natural and manmade water channels, especially those on plains and partially covered with trees and bushes. In this thesis, LiDAR data obtained around Bergama, Turkey, with the flying height of 1200 m, is used. LiDAR point measurements are influenced by three components: bare ground, above-ground objects, and noise. Our first purpose is to extract the vi ground surface from the above ground objects. A variety of methods are used for ground filtering of the LiDAR point cloud data, depending on the local environmental conditions. For the first aim of this study, a robust RANSAC based iterative strategy is proposed. The algorithm uses quadratic polynomial function in RANSAC mathematical model for local fitting to the LiDAR points as models of the ground surface. Generated surface patches are accepted based on the slope, residual distance from the inliers and percentage of inliers. Continuity of the surfaces from accepted neighboring patches are also used as a constraint. This way, regions grow from easy locations to complicated ones. Furthermore, for filling the gaps in the cleaned data where no fit could be reconstructed, Bézier surface fitting, which is a spline interpolation method, is iteratively applied to the points resulted from first stage. The second purpose of this study is to identify channel networks in complicated regions. Hence, curvature analysis is implemented using the Digital Terrain Model (DTM) product of first stage and quadratic fit coefficients in each neighborhood. Surface types are extracted from the estimated first and second fundamental forms and principal curvatures. Afterwards, channel hypotheses are formed based on valley surface type and geometric properties of the channel cross sections. When a cross section is accepted as a channel, the waterway is tracked on two perpendicular directions to extract the whole channel. The overall algorithm is tested on difficult areas and the success levels of DTM extraction and channel detection are shown quantitatively.


Flood Interaction with River Crossings: A Case Study
Yanmaz, Ali Melih (null, Springer, 1994-01-01)
Floods are natural hazards whose effects can deeply affect the economic and environmental equilibria of a region. Quality of life of people living in areas close to rivers depends on both the risk that a flood would occur and the reliability of flood forecast, warning and control systems. Tools for forecasting and mitigating floods have been developed through research in the recent past. Two innovations currently influence flood hazard mitigation, after many decades of lack of significant progress: they are...
Climate change impacts on lakes: an integrated ecological perspective based on a multi-faceted approach, with special focus on shallow lakes
Jeppesen, Erik; Meerhoff, Mariana; Davidson, Thomas A.; Trolle, Dennis; Sondergaard, Martin; Lauridsen, Torben L.; Beklioğlu, Meryem; Brucet, Sandra; Volta, Pietro; Gonzalez-Bergonzoni, Ivan; Nielsen, Anders (PAGEPress Publications, 2014-01-01)
Freshwater ecosystems and their biodiversity are presently seriously threatened by global development and population growth, leading to increases in nutrient inputs and intensification of eutrophication-induced problems in receiving fresh waters, particularly in lakes. Climate change constitutes another threat exacerbating the symptoms of eutrophication and species migration and loss. Unequivocal evidence of climate change impacts is still highly fragmented despite the intensive research, in part due to the...
Impact Assessment of Urban Regeneration Practices on Microclimate in The Context of Climate Change
Akköse, Gizem; Balaban, Osman; Department of Earth System Science (2022-2-10)
The annual ever-increase in population, urbanization, industrialization, and CO2 or greenhouse gas emissions brings with it important environmental crises. Climate change and urban heat islands (UHI) are crucial environmental crises that have serious consequences on the performance of the built environment and the comfort and health of users. Moreover, mass migrations from the urban areas and unhabitable cities are envisaged as a result of climate change. To minimize the impacts of climate change and ensure...
Extreme precipitation and drought monitoring in northeastern China using general circulation models and pan evaporation-based drought indices
Faiz, Muhammad Abrar; Liu, Dong; Fu, Qiang; Wrzesinski, Dariusz; Baig, Faisal; Nabi, Ghulam; Khan, Muhammad Imran; Li, Tianxiao; Cui, Song (2018-01-01)
The evaluation of precipitation extremes and the usage of appropriate drought indices are very important for assessment of natural disasters (i.e. floods and drought). For this purpose, we calculated values of indices that reflect precipitation extremes and 3 drought indices, i.e. the composite index (CI), standardized precipitation evapotranspiration index (SPEI), and reconnaissance drought index (RDI), with reformulation of pan evaporation and Penman-Monteith equations (denoted as CI-Pan, RDI-Pan, RDI-PM,...
PHPA as a frictional pressure loss reducer and its pressure loss estimation
Ercan, Can; Özbayoğlu, Evren; Department of Petroleum and Natural Gas Engineering (2007)
As the demand of oil and gas is increasing, using the existing reservoirs more efficiently as well as searching for new reservoirs is mandatory. Most undiscovered reservoirs are in deep or ultra-deep offshore locations, where drilling to such targets are very difficult with the available fluid circulation technology, since there exists a significant frictional pressure loss due to extreme long wellbores. In order to reduce the frictional pressure losses inside the drillstring, frictional drag reducers are u...
Citation Formats
A. Arghavanian, “CHANNEL DETECTION AND TRACKING FROM LIDAR DATA IN COMPLICATED TERRAIN,” Ph.D. - Doctoral Program, Middle East Technical University, 2022.