Patterns Of Rainfall Events Research Articles

Effects of rainfall pattern classification methods on the probability estimation of typhoon-induced debris-flow occurrence

ABSTRACT The frequent occurrence of typhoons causes geological disasters, such as debris flow and landslide, by bringing extreme rainfall events. Due to the lack of data collection on extreme rainfall events caused by typhoons, the relationship between rainfall patterns and debris flow has not been deeply studied. Therefore, based on hourly rainfall data during typhoons in Wenzhou from 1980 to 2017, this study used a variety of methods to classify the rainfall events and analyze the characteristics of typhoon-induced rainfall events and their impacts on the probability of debris-flow occurrence. Three classification techniques, including dynamic time warping, K-Means cluster, and self-organizing maps, are applied with two ways to normalize rainfall records, including dimensionless rainfall density curves and dimensionless rainfall cumulation curves, for extracting rainfall patterns from recorded 1 h rainfall data. The rainfall patterns are then used for the estimation of typhoon-induced debris-flow occurrence probability. Results show that different methods present different rainfall patterns. The probability of debris flows varies with different patterns of rainfall events. The research results help deepen the understanding of typhoon rainfall events and debris-flow disaster prevention in the region and contribute to regional flood control and disaster reduction.

Changes in Extremes Rainfall Events in Present and Future Climate Scenarios over the Teesta River Basin, India

Globally, changes in hydroclimate extremes such as extreme precipitation events influence water resources, natural environments, and human health and safety. During recent decades, India has observed an enormous increase in rainfall extremes during the summer monsoon (June to September) seasons. However, future extreme rainfall events have significant uncertainty at the regional scale. Consequently, a comprehensive study is needed to evaluate the extreme rainfall events at a regional river basin level in order to understand the geomorphological characteristics and pattern of rainfall events. In the above purview, the current research focuses on changes in extreme rainfall events obtained through observed gridded datasets and future scenarios of climate models derived through the Coupled Model Intercomparison Project (CMIP). The results highlight a significant rise in the extremes of precipitation events during the first half of the 21st century. In addition, our study concludes that accumulated precipitation will increase by five days in the future, while the precipitation maxima will increase from 200 to 300 mm/day at the 2-year, 50-year, and 100-year return periods. Finally, it is found that during the middle of the 21st century the 23.37% number of events will increase over the TRB at the 90th percentile.

Analytical solution for infiltration and deep percolation of rainwater into a monolithic cover subjected to different patterns of rainfall

Monolithic cover is increasingly considered for use at landfills of solid wastes in arid and semi-arid areas. The evaluation of the deep percolation of rainwater through the monolithic cover is required for the cover design. An analytical solution is developed in this study for evaluating the infiltration and deep percolation of rainwater into a monolithic cover, subject to different patterns of rainfall events. The analytical solution is derived from the simplified one-dimensional governing equation of unsaturated flow for an infinitely long monolithic cover by taking the exponential forms of the soil–water characteristic curve and the hydraulic conductivity curve into account. A unit gradient boundary (UG) is considered at the bottom boundary of the monolithic cover. The patterns of rainfall considered include uniform type (U), advanced type (A1 and A2), central-peaked type (C), and delayed type (D1 and D2). The delayed percolation after the completion of a rainfall event can be captured by the analytical solution. Numerical simulation is conducted to compare the results with the analytical solution and to demonstrate that the analytical solution is acceptable for describing a silty soil, which is commonly used as the material for a monolithic cover. The analytical solution is used to investigate the influence of the rainfall pattern on the infiltration process and the occurrence of deep percolation. The analytical solution is used to evaluate the total percolation of a monolithic cover subjected to a sequence of non-continuous rainfall events within a wet season. The evaluation accounts for the influence of the initial water storage in the cover on the percolation by using the antecedent rainfall method proposed by Crozier and Eyles in 1980. A case study is performed to demonstrate the evaluation approach by using the water balance monitoring data of a model test on a silty soil cover reported in the literature. The case study indicated that the total percolation from the analytical solution is 34% greater than the measurement, which was on the conservative side for practical application.

The Effect of Climate Change on Rainfall Trends and Flooding Risk in the West of Scotland

Evidence is presented of a general increase in river flows in four catchments in the West of Scotland in the last 30 years. The increase has been significantly higher than the increase in rainfall over the same period. It is postulated that the more than proportionate increase is due to changes in the distribution and pattern of rainfall events although changes in evapotranspiraiion rates are also considered.