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1.
Method to improve the mitigative effectiveness of a series of check dams against debris flows 总被引：2，自引：0，他引：2
The advance of technology has led to more competent countermeasures, but lives and properties still continue to suffer from water‐induced disasters, such as floods, landslides, and debris flows. To increase the effectiveness of counter systems, improved methods of planning and designing such systems are prerequisite. This paper describes briefly a methodological approach for predicting debris flow characteristics, and proposes techniques for evaluating and improving the mitigative effectiveness of check dams against debris flows in steep mountain torrents. Additionally, a non‐dimensional parameter, namely potential storage volume, is introduced to generalize the evaluation processes. As an example, the 1999 debris‐flow event in the San Julian River, Venezuela, is chosen for discussion. The paper also proposes a method of evaluating the control function of a series of check dams as well as the criteria for the selection of their sizes, numbers and locations. It is hoped that this work will help to determine which combinations of check dams will fit best together for the optimal control of debris flows and available resources in any river basin. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
2.
Koichi Watanabe Chinatsu Yachi Xiao Jing Song Saori Kakuyama Miyuki Nishibe Sheng Jun Jin 《Journal of Atmospheric Chemistry》2018,75(2):141-153
Measurements of the concentrations of H2O2 and methyl hydroperoxide (MHP), O3, and SO2 over Imizu City, Toyama Prefecture, Japan were performed in March using a helicopter. H2O2 concentrations were higher at an altitude of approximately 2,400 m (8,000 ft). The H2O2 concentrations (< 0.8 ppb) in the spring were much lower than those observed during the summer observations. MHP was also higher in the high-altitude atmosphere. Lower concentrations of H2O2 were observed when high air pollutants were actively transported from Asian continent. The concentrations of H2O2 were mostly lower than those of SO2; this condition is called oxidant limitation. If H2O2 concentration rises in cold months, the acidification of cloud water may be accelerated at high elevations in central Japan where air pollution is actively transported. 相似文献
3.
At four stations in Tokyo Bay, pore water profiles of dissolved organic carbon (DOC), nitrogen (DON), phosphorus (DOP), and inorganic nutrients were determined at 3-month intervals over 6 years. Concentrations of dissolved organic matter (DOM) and nutrients were significantly higher in pore waters than in the overlying waters. Pore water DOC, DON, and DOP concentrations in the upper most sediment layer (0–1 cm) ranged from 246 to 888 μM, from 14.6 to 75.9 μM, and from 0.02 to 9.83 μM, respectively. Concentrations of DOM and nutrients in pore waters occasionally showed clear seasonal trends and were highest in the summer and lowest in the winter. The seasonal trends in the pore water DOM concentrations were coupled with trends in the overlying water temperature and dissolved oxygen concentration. Benthic effluxes of DON and DOP were low compared with those of inorganic nutrients, accounting for only 1.0 and 1.5 % of the total benthic effluxes of nitrogen and phosphorus, respectively; thus benthic DOM fluxes were quantitatively insignificant to the inorganic nutrient fluxes in Tokyo Bay. The DOM fluxes represented about 7, 3, and 10 % of the riverine discharge of DOC, DON, and DOP to Tokyo Bay, respectively. 相似文献
4.
Stabilities of hexagonal new aluminous (NAL) phase and Ca-ferrite-type (CF) phase were investigated on the join NaAlSiO4-MgAl2O4 in a pressure range from 23 to 58 GPa at approximately constant temperature of 1,850 K, on the basis of in situ synchrotron
X-ray diffraction measurements in a laser-heated diamond-anvil cell. The results show that NAL is formed as a single phase
up to 34 GPa, NAL + CF between 34 and 43 GPa, and only CF at higher pressures in 40%NaAlSiO4-60%MgAl2O4 bulk composition. On the other hand, both NAL and CF coexist below 38 and 36 GPa, and only CF was obtained at higher pressures
in 60%NaAlSiO4-40%MgAl2O4 and 20%NaAlSiO4-80%MgAl2O4 composition, respectively. These results indicate that NAL appears only up to 46 GPa at 1,850 K, and CF forms continuous
solid solution at higher pressures on the join NaAlSiO4-MgAl2O4. NAL has limited stability in subducted mid-oceanic ridge basalt crust in the Earth’s lower mantle and undergoes a phase
transition to CF in deeper levels. 相似文献
5.
Saori Imada Kei Hirose Tetsuya Komabayashi Toshihiro Suzuki Yasuo Ohishi 《Physics and Chemistry of Minerals》2012,39(7):525-530
Compression behaviors of two Al-rich phases in the lower mantle, hexagonal new aluminum-rich (NAL) phase and its high-pressure polymorph Ca-ferrite-type (CF) phase, were examined for identical Na0.4Mg0.6Al1.6Si0.4O4 (40?% NaAlSiO4–60?% MgAl2O4) composition. The volumes of the NAL and CF phases were obtained at room temperature up to 31 and 134?GPa, respectively, by a combination of laser-annealed diamond-anvil cell techniques and synchrotron X-ray diffraction measurements. Fitting of the third-order Birch–Murnaghan equation of state to such pressure–volume data yields bulk modulus K 0?=?199(6) GPa at 1?bar and its pressure derivative K 0′?=?5.0(6) for the NAL phase and K 0?=?169(5) GPa and K 0′?=?6.3(3) for the CF phase. These results indicate that the bulk modulus increases from 397 to 407 GPa across the phase transition from the NAL to CF phase at 43 GPa, where the NAL phase completely transforms into the CF phase on Na0.4Mg0.6Al1.6Si0.4O4. Density also increases by 2.1?% across the phase transition. 相似文献
6.
Hydrodynamic characteristics of the Tam Pokhari glacial lake outburst flood in the Mt. Everest region,Nepal 总被引：1，自引：1，他引：0
The Tam Pokhari glacial lake outburst flood (GLOF), which occurred in 1998 in the Mt. Everest region of Nepal, was evaluated using hydrodynamic models to gain a better understanding of the flow behaviour. The flood wave was analysed separately under rigid and erodible boundary conditions. In both cases, the calculated dam‐breach hydrograph, which had a peak discharge of about 10 000 m3/s, was routed through the Inkhu River, which originates from the lake. The morphologic changes along the river were also analysed and the results were compared with satellite images, field observations and recorded data. In the case of rigid boundaries, the routing procedure gradually attenuated the peaks of the hydrographs to account for hydraulic pooling in narrow gorges and storage in the channel. In the case of erodible boundaries, such effects were minimized due to the increment in channel capacity associated with erosion by debris flow. The study revealed that the GLOF event produced a large‐scale debris flow. Additionally, the results revealed that erosion and deposition took place intermittently, but that approximately 440 000 m3 of sediment was deposited about 14 km downstream from the lake mouth. The calculated peak of the water and sediment mixture at 14·4 km was found to be 30 000 m3/s, which is almost 6 times as large as that observed when the rigid boundary conditions were used. Further, the increase in the peaks of the hydrographs due to sediment transport was the primary reason for the destruction associated with the GLOF. These findings suggest that the local sedimentology and topography, as well as other geo‐hazard conditions in the area, should be carefully evaluated before recommending any control measures against GLOFs in the Himalayan region. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
7.
Andrew J. Gooday Hiroshi Kitazato Saori Hori Takashi Toyofuku 《Journal of Oceanography》2001,57(3):377-384
Soft-shelled monothalamous foraminifera, including species belonging to the suborders Allogromiida and Astrorhizida (families Saccamminidae and Psammosphaeridae), are an abundant and diverse component of the meiofauna in the deep NE Atlantic but have never been systematically documented in the Pacific Ocean. We examined the 32–63 µm and >63 µm fractions of a sample (0–1 cm layer, surface area 52.8 cm2) from an abyssal plain in the subarctic North Pacific, close to the Aleutian Trench (48°05.43 N, 176°55.06 E; 5289 m water depth). The residues yielded an estimated 2876 stained foraminifera (=545 per 10 cm2) of which >75% occurred in the upper 0.5 cm layer and almost half in the 32–63 µm fraction. Rather less than a third (30.5%) of individuals, and about half of the morphospecies (56 out of 121), were soft-shelled monothalamous forms. Many of these, particularly the saccamminids, were tiny, <120 µm in maximum dimension. Based on our analysis of this sample, and previous results in the North Atlantic and NW Indian Oceans, we suggest that these poorly known taxa are a consistently important component of the abyssal meiofauna in well-oxygenated areas. 相似文献
8.
Silica deficient Mg-Al granulites from Paramati within the Palghat-Cauvery Shear System contain sapphirine in association with corundum, spinel and sillimanite. Gedrite, which occurs commonly in this locality, coexists with cordierite, corundum and sillimanite. Mineral assemblages and reaction textures indicate peak metamorphism at ultrahigh- temperature conditions. This new locality provides evidence for extreme crustal metamorphism along the Archean-Proterozoic collision boundary in southern India. 相似文献
9.
Hideki Iwano Tohru Danhara Yugo Danhara Saori Hirabayashi Toru Nakajima Harutaka Sakai Takafumi Hirata 《Island Arc》2020,29(1)
We present a new LA–ICP–MS system for zircon fission‐track (FT) and U–Pb double dating, whereby a femtosecond laser combined with galvanometric optics simultaneously ablates multiple spots to measure average surface U contents. The U contents of zircon measured by LA–ICP–MS and standardized with the NIST SRM610 glass are comparable to those measured by the induced FT method, and have smaller analytical errors. LA–ICP–MS FT dating of seven zircon samples including three IUGS age standards is as accurate as the external detector method, but can give a higher‐precision age depending on the counting statistics of the U content measurement. Double dating of the IUGS age standards gives FT and U–Pb ages that are in agreement. A chip of the Nancy 91500 zircon has a homogeneous U content of 84 ppm, suggesting the possibility of using this zircon as a matrix‐matched U‐standard for FT dating. When using the Nancy 91500 zircon as a U‐standard, a zeta calibration value of 42–43 year cm2 for LA–ICP–MS FT dating is obtained. While this value is strictly valid only for the particular session, it can serve as a reference for other studies. 相似文献
10.
In this study, the characteristic of multiple glacial lake outburst floods (GLOFs) in the Pho Chu River basin in Bhutanese Himalayas is evaluated to help assess the potential impact. Thorthormi Cho (TC) and Lugge Cho (LC) in the east branch and two unnamed lakes labelled A and B in the west branch of Pho Chu are chosen for the study. Numerical models were employed to simulate different involved processes. The results show that the peak sediment discharge in the east branch of the Pho Chu River by the TC dam breach reached about 5000 m3/s (during the first GLOF) at 4 km whereas by the LC dam breach is about 600 m3/s (second GLOF) at 6 km. However, the highest peak hydrographs (sediment and water mixture) calculated during the first and second GLOF are about 10 000 m3/s at the 18‐km section and about 23 000 m3/s at the 10‐km section, respectively. In the west branch of Pho Chu, erosion and depositions are the frequent intermittent local processes during the first GLOF event from Lake A. Because the first event stabilized the irregular river bed profile, there is not much sediment discharge developed during the second GLOF from Lake B. At the 17‐km section of the west branch, the peak hydrograph reached about 9000 m3/s during the first event against the peak of about 800 m3/s during the second event. The results suggest that even if multiple dam breaches occur simultaneously, GLOF surges pass through the main river channel at different times with very different flood characteristics. The differences in travel time and flood characteristics mostly depend on the distributions of bed slope and potential erosion depth along the reach. Further, the amount of sediment accumulated in and transported by each surge is reliant on the temporal geomorphologic setting of the river and therefore on the impact of the previous GLOF on riverbed profile and potential erosion depth. The robustness in peak GLOF hydrographs is associated with sediment flow dynamics. As a consequence, serious inundation of Punakha, Lobeysa and major portion of Wangdue Phodrang is anticipated. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献