• Journal of Ecology and Environment
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• v.44 no.3
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• pp.196-206
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• 2020

Background: The Himalayan forests are of great importance to sustain the nature and community resource demands. These forests are facing pressures both from anthropogenic activities and ongoing global climatic changes. Poor natural regeneration has been considered a major problem in mountainous forests. To understand the population structure and regeneration status of Larix (Larix griffithiana and Larix himalaica), we conducted systematic vegetation surveys in three high-altitude valleys namely Ghunsa (Kanchenjunga Conservation Area, KCA), Langtang (Langtang National Park, LNP), and Tsum (Manaslu Conservation Area, MCA) in Nepal Himalaya. The average values of diameter at breast height (DBH), height, and sapling height were compared for three sites and two species using Kruskal-Wallis test. Population structure was assessed in terms of proportion of seedlings, saplings, and trees. Regeneration was analyzed using graphical representation of frequencies of seedlings, saplings, and trees in histograms. Results: The results showed that the population structure of Larix in terms of the proportion of seedling, sapling, and tree varied greatly in the three study areas. KCA had the highest record of seedling, sapling, and tree compared to other two sites. Seedlings were the least among three forms and many plots were without seedlings. We found no seedling in MCA study plots. The plot level average DBH variation among sites was significant (Kruskal-Wallis χ² = 7.813, df = 2, p = 0.02) as was between species (Kruskal-Wallis χ² = 5.9829, df = 1, p = 0.014). Similarly, the variation in average tree height was significant (Kruskal-Wallis χ² = 134.23, df = 2, p < 0.001) among sites as well as between species (Kruskal-Wallis χ² = 128.01, df = 1, p < 0.001). All the sites showed reverse J-shaped curve but more pronounced for KCA and MCA. In comparing the two species, Larix griffithiana has clear reverse J-shaped diameter distribution but not Larix himalaica. Conclusion: The varied responses of Larix manifested through regeneration status from spatially distinct areas show that regeneration limitations might be more pronounced in the future. In all the three studied valleys, regeneration of Larix is found to be problematic and specifically for Larix griffithiana in MCA and Larix himalaica in LNP. To address the issues of disturbances, especially serious in LNP, management interventions are recommended to sustain the unique Himalayan endemic conifer.

• Journal of Korean Society for Geospatial Information Science
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• v.24 no.1
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• pp.17-24
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• 2016

At present, summer cloudburst and local torrential rainfalls have increased in this country, because of climatic change. Therefore, studies on prevention of soil loss have been actively proceeded, and Korea Forest Service has offered landslide hazard map. Landslide hazard map divides risks into 5 classes, by giving weight with 9 kinds of elements. In August 25 2014, soil loss occurred in the whole Oryun Tunnel, Geumjeong-gu, Busan, because of local torrential heavy rain. As a result of comparing with landslide hazard map, the area where soil loss occurred in reality is a safety zone on hazard map. Rainfall, soil map, geological map, forest type map, gradient, drainage network, watershed, basin shape, and efflux of the whole Oryun Tunnel where soil loss occurred were analyzed. As a result of an analysis, it is judged that soil, forest type, much efflux and peak discharge, degree of water network and basin shape of a place where landslide occurred are causes of soil loss. It is judged that efflux, peak discharge, and basin shape by the localized rainfall that is not considered in landslide hazard map of them are the biggest causes of soil loss. It is judged that efflux, peak discharge, degree of water network and basin shape by the rainfall are important through a study on a causual analysis on soil loss in the whole Oryun Tunnel where is one of occurrence area where a lot of propertywere lost by the record local torrential rainfalls. A localized torrential downpour should be prepared by considering these elements on judgement of a landslide hazard area.

• Journal of the Society of Disaster Information
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• v.9 no.4
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• pp.503-510
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• 2013

Recently, localized heavy rain is increased by climatic changes and landslide is increased. Also, because of landslide occurred in urban area, life and property damages are increased. Therefore, standard operation procedure of disasters should be established by steps and institutions so as to respond landslide. This thesis investigated application of current disaster manual so as to write SOP of landslide for disaster prevention related experts and accepted opinion for responding necessaries by using landslide SOP and important matters by step of disaster management. As the result of investigation, application of manual was low during the current response to disasters and application was the highest in responding step among the steps of disaster management. In case of landslide, they responded that response with SOP is necessary. During the organization of landslide SOP, they responded that training and education for landslide disaster are important at the step of prevention, conduction of landslide disaster broadcasting and provision of information are important at the step of preparation, guidance for evasion and behavior methods is important at the step of response and investigation of landslide disaster damages and reflection of record and evaluation are important at the step of recovery. In addition, for the requests for landslide SOP application, there was an importance of secondary factors such as expansion of professional manpower, strengthening of law and institution, education and training for SOP acquisition, etc.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.3
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• pp.75-87
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• 1980

Most hydro]ogic phenomena are the complex and organic products of multiple causations like climatic and hydro-geological factors. A certain significant correlation on the run-off in river basin would be expected and foreseen in advance, and the effect of each these causual and associated factors (independant variables; present-month rainfall, previous-month run-off, evapotranspiration and relative humidity etc.) upon present-month run-off(dependent variable) may be determined by multiple regression analysis. Functions between independant and dependant variables should be treated repeatedly until satisfactory and optimal combination of independant variables can be obtained. Reliability of the estimated function should be tested according to the result of statistical criterion such as analysis of variance, coefficient of determination and significance-test of regression coefficients before first estimated multiple regression model in historical sequence is determined. But some error between observed and estimated run-off is still there. The error arises because the model used is an inadequate description of the system and because the data constituting the record represent only a sample from a population of monthly discharge observation, so that estimates of model parameter will be subject to sampling errors. Since this error which is a deviation from multiple regression plane cannot be explained by first estimated multiple regression equation, it can be considered as a random error governed by law of chance in nature. This unexplained variance by multiple regression equation can be solved by stochastic approach, that is, random error can be stochastically simulated by multiplying random normal variate to standard error of estimate. Finally hybrid model on estimation of monthly run-off in nonhistorical sequence can be determined by combining the determistic component of multiple regression equation and the stochastic component of random errors. Monthly run-off in Naju station in Yong-San river basin is estimated by multiple regression model and hybrid model. And some comparisons between observed and estimated run-off and between multiple regression model and already-existing estimation methods such as Gajiyama formula, tank model and Thomas-Fiering model are done. The results are as follows. (1) The optimal function to estimate monthly run-off in historical sequence is multiple linear regression equation in overall-month unit, that is; Qn=0.788Pn+0.130Qn-1-0.273En-0.1 About 85% of total variance of monthly runoff can be explained by multiple linear regression equation and its coefficient of determination (R2) is 0.843. This means we can estimate monthly runoff in historical sequence highly significantly with short data of observation by above mentioned equation. (2) The optimal function to estimate monthly runoff in nonhistorical sequence is hybrid model combined with multiple linear regression equation in overall-month unit and stochastic component, that is; Qn=0. 788Pn+0. l30Qn-1-0. 273En-0. 10+Sy.t The rest 15% of unexplained variance of monthly runoff can be explained by addition of stochastic process and a bit more reliable results of statistical characteristics of monthly runoff in non-historical sequence are derived. This estimated monthly runoff in non-historical sequence shows up the extraordinary value (maximum, minimum value) which is not appeared in the observed runoff as a random component. (3) "Frequency best fit coefficient" (R2f) of multiple linear regression equation is 0.847 which is the same value as Gaijyama's one. This implies that multiple linear regression equation and Gajiyama formula are theoretically rather reasonable functions.

• Journal of Korea Water Resources Association
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• v.46 no.6
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• pp.613-627
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• 2013

In this study, to understand the May aridity condition of each region for the year of the worst drought on record in each duration (1-, 3-, 6-, 12-, 24 months), monthly climate data recorded from 1973 to 2006 at 53 climatological stations in South Korea were used to estimate the FAO Penman-Monteith reference potential evapotranspiration (RET). Monthly precipitation and RET were used to estimate P/RET as aridity index and variation index (VI) of P/RET, and these indexes are compared with SPI (Standard Precipitation Index). Fifty three climatological stations were grouped into 20 regions, so that May aridity conditions of 20 regions were studied. Furthermore, regional trend of May aridity index was studied by applying Mann-Kendall trend analysis, Spearman rank test, and Sen's slope estimator. The study results show that variation index (VI) of P/RET and SPI have close correlation. Throughout the country, as the duration is shorter, May aridity was more severe. In case of 3-month and 6-month duration, most of region show significant or non-significant decreasing trend of aridity index. However, no region show significant decreasing trend of aridity index in case of 12-month and 24-month duration.

• Economic and Environmental Geology
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• v.34 no.2
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• pp.217-226
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• 2001

Stable isotope, paleoceanographic and sedimentological analyses were carried out along the core Ml5612 from the Mid-Atlantic Ridge. Distinct negative ${\delta}^{18}O anomalies punctuate the planktonic isotope records and correlate with the Heinrich-IRD cvents. The IRD layer in the corc contains varying amounts of quartz, K-feldspar, plagioclase, calcite, dolomite and mica, in which detrital carbonate contributes between I and 13% (except H3 and H6). Anomalies are strongest in the N. pachydenna (sin.) isotope record. Systematic changes in the ${\delta}^{18}O offset of G. hul/aides and G. inJlata signify variations in mid-latitude thermocline structure. In conjunction with negative benthic ${\delta}^{13}C anomalies, the data document a stronger contribution of a ${\delta}^{13}C depleted, nutrient-rich water mass during the IRD events. The ${\delta}^{13}C amplitude of > 1 $\textperthousand$ between 25 and 57 ka indicates changes between northern source (NADW) and southern source (AABW) water masses at this site. The IRD layers in the core Ml56l2 are correlative with those from the core S075-26KL and DSDP 609. The IRD layers from the Portuguese margin arc coeval with HI, H2 and H4 of the open North Atlantic. This similarity (and/or synchronicity in both regions may have been resulted from common changes in a North Atlantic thermohaline switch.

• Atmosphere
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• v.17 no.4
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• pp.471-481
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• 2007

Temperature and precipitation, particularly August and summer, in the Korean peninsular are analyzed. The analyzed period is 1973-2007 for the Korean peninsular (that is, 60 meteorological station average). In addition, 100 year record (1908-2007) of temperature and precipitation in Seoul are also analyzed. Results indicate that the temperatures (mean, maximun, and minimum) of August and summer of 2007, both in Korean peninsular and Seoul, are higher than normal. The increasing rate of minimum temperature for the August and summer during the period from 1973 to 2007 shows greater than the mean and maximum temperature both in Korean peninsular and Seoul due to the global warming and urbanization. Number of tropical night days, defined by the days with above $25^{\circ}C$ in minimum temperature, shows increasing trend both in August and summer from 1973 to 2007 due to the combination effect of the global warming and urbanization. The amount of precipitation, both in August and summer, for Korean peninsular and Seoul shows increasing trend from 1973 to 2007, and 1908 to 2007, respectively. Amount of precipitation and rainy days, both August and summer, during 2000s show greater than those of the 1970s both in Korean peninsular and Seoul. Extreme rainy days (greater than 120mm/day, greater than 80mm/day, greater than 30mm in any 1-hour period and greater than 10mm in any 10-minute period) show increasing trend from 1973 to 2007 for both in August and in summer.