Comparison between FLO-2D and Debris-2D on the Application of Assessment of Granular Debris Flow Hazards with Case Study

Numerical simulation has been widely applied to the assessment of debris flow hazards. In East Asia and especially Taiwan, the most widely used numerical programs are FLO-2D and Debris-aD. Although these two programs are applied to the same engineering tasks, they are different in many aspects. These two programs were compared according to their fundamental theories, input and output data, computational algorithms and results. Using both programs, the simulations of a real debris flow with abundant granular material induced by landslides at Xinfa village in southern Taiwan are performed for comparison. The simulation results show that Debris- 2D gives better assessment in hazard area delineating and flow depth predicting. Therefore, Debris-2D is better for simulation of granular debris flows.

GULLY-SPECIFIC DEBRIS FLOW HAZARD ASSESSMENT IN CHINA

Techniques of gully-specific debris flow hazard assessment develope d in four periods since the end of the 1980s have been discussed in the present paper. The improvement for the empirical assessment method is the sectionalized function transformation for the factor value, rather than the classified logical transformation. The theoretical equation of the gully-specific debris flow haz ard is expressed as the definite integral of an exponential function and its num erical solution is expressed by the Poisson Limit Equation. Current methods for assessment of debris flow hazard in China are still valid and practical. The fur ther work should be put on the study of the reliability (or uncertainty) of the techniques. For the future, we should give a high priority to the relationship b etween debris flow magnitude and its frequency of occurrence, make more developm ents of prediction model on debris flow magnitude, so as to finally reach the go al of assessing the hazard of debris flow by theoretical model, and realize both actuality assessment and prediction appraisal of debris flow.

Debris flow susceptibility and propagation assessment in West Koyulhisar, Turkey

Turkey is highly prone to landslides because of the geological and geographic location.The study area,which is located in a tectonically active region,has been significantly affected by mass movements.Flow type landslides are frequently observed due to this location.This study aims at determining the source area and propagation of debris flows in the study area.We used the heuristic method to extract source areas of debris flow,and then used receiver operating characteristic(ROC)curve analysis to assess the performance of the method,and finally calculated the Area under curve(AUC)values being 83.64%and 80.39%for the success rate and prediction rate,respectively.We calculated potential propagation area and runout distance with Flow-R software.In conclusion,the obtained results(susceptibility map,propagation and runout distance)are very important for decisionmakers at the region located on an active fault zone,which is highly prone to natural disasters.The outputs of this study could be used in site selection studies,designing erosion prevention systems and protecting existing human-made structures.

A Modified Certainty Coefficient Method(M-CF) for Debris Flow Susceptibility Assessment:A Case Study for the Wenchuan Earthquake Meizoseismal Areas

In the meizoseismal areas hit by the China Wenchuan earthquake on May 12, 2008, the disasterprone environment has changed dramatically, making the susceptibility assessment of debris flow more complex and uncertain. After the earthquake, debris flow hazards occurred frequently and effective susceptibility assessment of debris flow has become extremely important. Shenxi gully in Du Jiangyan city, located in the meizoseismal areas, was selected as the study area. Based on the research of disaster-prone environment and the main factors controlling debris flow, the susceptibility zonations of debris flow were mapped using factor weight method(FW), certainty coefficient method(CF) and geomorphic information entropy method(GI). Through comparative analysis, the study showed that these three methods underestimated susceptible degree of debris flow when used in the meizoseismal areas of Wenchuan earthquake. In order to solve this problem, this paper developed a modified certainty coefficient method(M-CF) to reflect the impact of rich loose materials on the susceptible degree of debris flow. In the modified method, the distribution and area of loose materials were obtained by field investigations and postearthquake remote sensing image, and four data sets, namely, lithology, elevation, slop and aspect, wereused to calculate the CF values. The result of M-CF method is in agreement with field investigations and the accuracy of the method is satisfied. The method has a wide application to the susceptibility assessment of debris flow in the earthquake stricken areas.

Risk assessments of debris flow based on improved analytic hierarchy process and efficacy coefficient method

In order to evaluate the danger of debris flow properly, eight factors were selected as the risk assess- ment indexes of the debris flow, namely the vertical slope, valley relative difference, hillside slope, area of ba- sin, loose solid material reserves, the path length of sediment supply probability, silting and scouring derrieking and vegetation coverage. The improved Analytic Hierarchy Process （ AHP ） method was used to obtain the weights of the factors; and the efficacy coefficient method was adopted to evaluate the risks of six typical debris flow gullies. According to the research, the improved AHP method not only avoids the subjectivity in the indi- vidual factor valuation by comparing two factors of each layer, but also makes the subsequent consistency check unnecessary.

Experimental Investigation of the Effect of Bow Profiles on Resistance of an Underwater Vehicle in Free Surface Motion

In this paper, towing tank experiments are conducted to study the behavior of flow on a model of the underwater vehicle with various shapes of bows, i.e. tango and standard bows in free surface motion tests. The total resistances for different Froude numbers are considered experimentally. The towing tank is equipped with a trolley that can operate in through 0.05-6 m/s speed with ±0.02 m/s accuracy. Furthermore, the study is done on hydrodynamic coefficients i.e. total, residual and friction resistance coefficients, and the results are compared. Finally, the study on flow of wave fields around bows is done and wave filed around two bows are compared. The Froude number interval is between 0.099 and 0.349. Blockage fraction for the model is fixed to 0.005 3. The results showed that the residual resistance of the standard bow in 0.19 to 0.3 Froude number is more than the tango bow in surface motion which causes more total resistance for the submarine. Finally, details of wave generated by the bow are depicted and the effects of flow pattern on resistance drag are discussed.

Assessment of angiographic coronary slow flow phenomenon with intracoronary ultrasound and doppler flow mapping

In order to study the mechanism of angiographic coronary slow flow phenomenon (SF), intracoronary ultrasound (ICUS) and Doppler (ICD) were performed in 14 patients with angiographic SF phenomenon but with normal angiograms and in 16 patients with normal angiographic coronary flow (NF). A 3.5 F, 20 MHz ultrasound catheter (Boston Scientific) was used for ICUS and a 0.014 inch FloWire (Cardiometrics) was used for ICD. Coronary flow velocity including average peak velocity (APV), maximal peak velocity (MPV) at rest and at hyperemia as well as coronary flow reserve (CFR) were compared in both groups in comparison to the presence or absence of plaque formation based on ICUS. CFR in the SF group (4.2±1.1) was even higher than that of the NF group (3.1±0.6, P<0.001). Department of Cardiology, University GHS Essen, Germany (Ge JB, Simon H, Jeremias A, Liu FQ, Grge G, Haude M, Baumgart D and Erbel R) Significant differences were also found concerning the APV and MPV among both groups (both P <0.001). Plaque formation was found in 7/13 patients with a lumen reduction of 21%±24% in SF group and in 7/16 of the NF group with a lumen reduction of 19%±17%. Comparison of APV, MPV and CFR in SF and NF grups. Comparison of APV, MPV and CFR in SF and NF groups[BHDFG1*2,WK8ZQ1,WK11DW,WK11DWW] SF group NF groupAPV (cm/s) Rest 7.7±2.0 21.1±5.0 * Peak31.7±14.961.3±14.2 *MPV (cm/s) Rest17.4±4.637.0±11.4 * Peak56.8±14.981.8±17.7 *CFR4.2±1.13.1±0.6 # * P<0.001, #P=0.002. Coronary slow flow phenomenon in angiography indicates reduced resting flow velocity without reduction of coronary flow reserve.

An assessment on the wideband and narrowband methods for ultrasonic blood flow measurements

A comparison study on the ultrasonic blood flow estimation methods is carried out in this paper. The methods are divided into two classes-narrowband and wideband techniques.The pulsed Doppler systems and the autocorrelation methods are essentially the narrowband estAnators. They give the results with low velocity resolution and probably the aliased spectrum.The wider the frequency band of the signals, the worse the results. Time domain crosscorrelation technique, wideband makimum likelihood estimation and 2D Fourier transform method are three wideband techniques. The high velocity resolution and the ability of anti-aliasing are shown by these wideband estimation strategies.