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A new crack detection approach based on local binary patterns (LBP) with support vector machine (SVM) was proposed in this paper. The propsed algorithm can extract the LBP feature from each frame o...

In this letter, we propose a method to model architectural components in large-scale indoor spaces from point cloud measurements. The proposed method enables the modeling of curved surfaces, cylindrical pillars, and slanted surfaces, which cannot be modeled using existing approaches. It operates by constructing the architectural points from the raw point cloud after removing non-architectural (objects) points and filling in the holes caused by their exclusion. Then, the architectural points are represented using a set of piece-wise planar segments. Finally, the adjacency graph of the planar segments is constructed to verify the fact that every planar segment is closed. This ensures a watertight mesh model generation. Experimentation using 14 different real-world indoor space datasets and 2 public datasets, comprising spaces of various sizes—from room-scale to large-scale (12,557 m $^{2}$ ), verify the accuracy of the proposed method in modeling environments with curved surfaces, cylindrical pillars, and slanted surfaces.

In this study, the time–area curve of an ellipse is analytically derived by considering flow velocities within both channel and hillslope. The Clark IUH is also derived analytically by solving the continuity equation with the input of the derived time–area curve to the linear reservoir. The derived Clark IUH is then evaluated by application to the Seolmacheon basin, a small mountainous basin in Korea. The findings in this study are summarized as follows. (1) The time–area curve of a basin can more realistically be derived by considering both the channel and hillslope velocities. The role of the hillslope velocity can also be easily confirmed by analyzing the derived time–area curve. (2) The analytically derived Clark IUH shows the relative roles of the hillslope velocity and the storage coefficient. Under the condition that the channel velocity remains unchanged, the hillslope velocity controls the runoff peak flow and the concentration time. On the other hand, the effect of the storage coefficient can be found in the runoff peak flow and peak time, as well as in the falling limb of the runoff hydrograph. These findings are also confirmed in the analysis of rainfall–runoff events of the Seolmacheon basin. (3) The effect of the hillslope velocity varies considerably depending on the rainfall events, which is also found to be mostly dependent upon the maximum rainfall intensity.

In this study, a storm event-based frequency analysis method was proposed to mitigate the limitations of conventional rainfall depth–duration–frequency (DDF) analysis. The proposed method takes the number, rainfall depth, and duration of rainstorm events into consideration and is advantageous in estimation of more realistic rainfall quantiles for a given return period. For the purpose of hydraulics design, the rainfall depth thresholds are incorporated to retrieve the rainstorm events for estimating design rainfalls. The proposed method was tested against the observed rainfall data from 1961 to 2010 at Seoul, Korea and the computed rainfall quantiles were compared with those estimated using the conventional frequency analysis method. The study results indicated that the conventional method was likely to overestimate the rainfall quantiles for short rainfall durations. It represented that the conventional method could reflect rainfall characteristics of actual rainstorm events if longer durations (like 24 hours) were considered for estimation of design rainfalls.

In this study, the annual maximum rainfall event series were constructed and compared for both the modern flip-bucket type rainfall data, collected since 1961 (the modern data), and the old Chukwooki rainfall data, collected from 1777 to 1910 (the Chukwooki data). First, independent rainfall events were derived, by applying the same rainfall threshold of 2 mm and data collection time interval of 2 hours, to both the Chukwooki and the modern data. Annual maximum rainfall event series were then constructed, by applying Freund's bivariate exponential distribution annually. Finally, bivariate frequency analysis was done for the annual maximum rainfall event series constructed, by applying the bivariate logistic model to evaluate and quantify their characteristics. The results are in summary: (1) characteristics of the Chukwooki rainfall events and modern rainfall events are very similar to each other; (2) the annual maximum rainfall events of modern data are slightly larger than those of the Chukwooki data. The total rainfall depth per rainfall event for any given return period is thus estimated to be a little higher for the modern data than that of the Chukwooki data. However, based on the findings in this study, it could not be concluded that the rainfall characteristics have significantly changed during the last 200 years.

Three different nonlinear models – an exponential function model, a logarithmic function model, and a power function model – were evaluated as possible candidates for the storage–outflow relationship of a reservoir. Also, the storage coefficient was derived by analyzing the impulse response function of the reservoir. Additionally, by applying the theoretical results, the storage coefficients of four dam reservoirs in the Han River Basin, Korea, were estimated and evaluated with respect to the dam reservoir and basin characteristics. Summarizing the results, first, only the exponential function model was found to provide a realistic storage coefficient for a reservoir. Second, the storage coefficient was found to be strongly and linearly proportional to the flood control volume divided by the channel length.

This paper proposes a novel hybrid method for flood susceptibility mapping using a geographic information system (ArcGIS) and satellite images based on the analytical hierarchy process (AHP). Here, the following nine multisource environmental controlling factors influencing flood susceptibility were considered for relative weight estimation in AHP: elevation, land use, slope, topographic wetness index, curvature, river distance, flow accumulation, drainage density, and rainfall. The weight for each factor was determined from AHP and analyzed to investigate critical regions that are more vulnerable to floods using the overlay weighted sum technique to integrate the nine layers. As a case study, the ArcGIS-based framework was applied in Seoul to obtain a flood susceptibility map, which was categorized into six regions (very high risk, high risk, medium risk, low risk, very low risk, and out of risk). Finally, the flood map was verified using real flood maps from the previous five years to test the model’s effectiveness. The flood map indicated that 40% of the area shows high flood risk and thus requires urgent attention, which was confirmed by the validation results. Planners and regulatory bodies can use flood maps to control and mitigate flood incidents along rivers. Even though the methodology used in this study is simple, it has a high level of accuracy and can be applied for flood mapping in most regions where the required datasets are available. This is the first study to apply high-resolution basic maps (12.5 m) to extract the nine controlling factors using only satellite images and ArcGIS to produce a suitable flood map in Seoul for better management in the near future.

In this study, flood records in the Annals of the Choson Dynasty (1392–1910) were considered for the frequency analysis of rainfall in Seoul, Korea. The old Korean rain gauge (Chukwooki) data (1777–1907) were also used to evaluate major flood records in the Annals of the Choson Dynasty. The design rainfalls were estimated using the binomial censored data maximum likelihood estimator. The results can be summarized as follows. (1) The frequency analysis was done for 24 h rainfall amounts as this was assumed to represent the three different rainfall records well: the documentary records in the Annals of the Choson Dynasty, the Chukwooki data and the modern data. Also, given the possible uncertainty level of the classification results of the documentary records, only 19 catastrophic events (the highest level of flood) were considered in the frequency analysis. The threshold value was decided to be 388 mm by comparing the documentary records with the Chukwooki data. (2) The sensitivity analysis shows that the effects of the threshold value, the number of catastrophic records, and the accuracy level of the flood records in the Annals of the Choson Dynasty on the frequency analysis results are very limited. That is, the length of the flood records in the Annals of the Choson Dynasty was found to be long enough to overcome the possible uncertainty of the flood records. (3) The design rainfalls estimated by taking into account the flood records in the Annals of the Choson Dynasty were found to be very similar to those for the modern data. However, the confidence intervals estimated by considering all the records available were found to be just one third of those of the modern data.

A real world reconstruction that generates cyberspace not from a computer graphics tool, but from the real world, has been one of the main issues in two different communities of robotics and computer vision under different names of Simultaneous Localization And Mapping (SLAM) and Structure from Motion (SfM). However, there have been few trials that actively integrate SLAM and SfM for possible synergy. This paper shows the real world reconstruction can be enabled through this integration. As a result, the preliminary map has been generated of which five subgoals are: Realistic view (RGB), accurate geometry (depth), applicability to multi-floor indoor building, initial classification of a possible set of objects, and full automation. To this end, an engineering framework of “Acquire-Build-Comprehend (ABC)” is proposed, through which a sensor system acquires an RGB-Depth point cloud from the real world, builds a three-dimensional map, and comprehends this map to yield the possible set of objects. Its...

In indoor environments, there exists a few distinctive indoor spaces’ features (ISFs). However, up to our knowledge, there is no algorithm that fully utilizes ISF for accurate 3-D SLAM. In this letter, we suggest a sensor system that efficiently captures ISF and propose an algorithm framework that accurately estimates sensor’s 3-D poses by utilizing ISF. Experiments conducted in six representative indoor spaces show that the accuracy of the proposed method is better than the previous method. Furthermore, the proposed method shows robust performances in a sense that a set of adjusted parameters of the related algorithms does not need to be recalibrated as target environment changes. We also demonstrate that the proposed method not only generates 3-D depth maps but also builds a dense 3-D RGB-D map.

In this study, a new evaluation method for the water supply safety of a dam is proposed. This method considers both climatic conditions and storage characteristics of a dam. The annual vari...

In this study, a parsimonious framework for supporting Water Sensitive Urban Design (WSUD) was proposed to seek a tradeoff between investment of WSUD features and mitigation of urban flood damage. A two-dimensional (2D) hydrological-hydraulic simulation model, PCSWMM, was adopted to simulate the rainfall-runoff process and inundation scenarios, and the flood damages was evaluated based on inundated water depths and damage curves. The sensitivity of deploying various design features to flood control effects was also tested, which provided useful information for identifying potential design parameters (like conduit sizes and pond locations). The proposed framework was applied to a hypothetical case adapted from an urban district in the tropical region considering various WSUD features (i.e. rainwater storage pond, rain garden, and conduit upgrading). The results showed that when the gross investment of WSUD features increased from 0 to 1.19 million $, the damage cost would decrease from 4.61 to 3.41 million $; a linear relationship (with a R-square fit at 0.9) was found suitable to represent the relationship between the investment and the damage. The proposed framework is effective in helping assess the balance between mitigation of urban flood damage and adoption of WSUD features, and could be used to support urban water managers for a more science-based decision making towards flood risk management. MOE (Min. of Education, S’pore) Published version

This study investigates the effect of the merging of subbasins on the storage coefficient of the entire basin with the concept of parallel and serial systems of linear reservoirs having dif...

In this study, four infiltration facilities (permeable pavement, infiltration gutter, infiltration trench, and infiltration well) have been investigated and compared with their flood runoff reduction effect. The SEEP/W model was used to estimate the infiltration amount of each facility, and the flood runoff reduction effect was quantified by the decrease in curve number (CN). As a result of this study, we found that: (1) the infiltration could be successfully simulated by the SEEP/W model, whose result could also be quantified effectively by the decrease in CN; (2) among the four infiltration facilities considered in this study, the infiltration well and infiltration trench were found to be most efficient and economical; (3) finally, the intervention effect of the nearby infiltration facility was found not so significant. In an extreme case where the infiltration wells were located at 1 m interval, the intervention effect was found to be just 1%.

This study investigated the possible problems of using the concept of critical rainfall duration (CRD) for estimating the design flood. The investigation focused on the evaluation of the difference between the annual maximum independent rainfall event series (IRES) and the annual maximum short-duration rainfall series in Seoul, Korea. Annual maximum IRES was determined by applying Freund’s bivariate exponential distribution, which were also used for frequency analysis by applying the Gumbel’s bivariate logistic model. Both the annual maximum IRES and the frequency analysis results were then compared with those of the conventional annual maximum fixed-duration rainfall series (FDRS). The results are summarized as follows. First, the mean rainfall intensity of the annual maximum IRES was found to be little changed regardless of their durations. Thus, most of the annual maximum short-duration rainfall series would be selected in the annual maximum IRES. Second, results of the bivariate frequency anal...