Rainfall Intensity Duration Curves Research Articles

Investigation of different lahar types with rainfall intensity duration curves in Arimura river basin of Sakurajima volcano

Investigation of different lahar types with rainfall intensity duration curves in Arimura river basin of Sakurajima volcano

Assessment of the drainage systems performance in response to future scenarios and flood mitigation measures using stormwater management model

Urban Flooding represents a significant problem in developing urban areas caused by inadequate stormwater drainage systems, increased impervious surface areas, and climate change. The performance of drainage systems can be evaluated using simulation models such as the stormwater management simulation model (SWMM). In this study, the potential impacts of future design rainfall on the performance of stormwater management systems were assessed by altering a hyetograph derived from rainfall intensity duration curves from three climate models. In addition, the effects of continued urbanization on the systems have been simulated by changing the percentage of imperviousness from current land use conditions. According to the findings, existing drainage systems cannot manage the expected flooding risks caused by a slight change in future rainfall intensity under each climate model. As a result of urban development, increasing the imperviousness ratio from 10% to 70% has increased peak runoff from 51.3 to 82.4 m3/s, flooding volume amplified from 24,320.5 x103 to 33,647.4 x103 m3 (representing 38.4% of the increase), and flooded nodes risen from 64 to 196 (representing 67.12% of raise). Overall, flooding locations and magnitude were identified, while drainage systems failed to safely convey surface runoff at baseline conditions, implying that future flooding will be more intense. As a result, selected mitigation strategies should be considered to alleviate the flooding risks that disrupt the socio-economic environment and the resulting significant property and life losses in Dodola, Ethiopia.

Deformation and failure mechanism of colluvial landslide under sustained rainfall-a case study of Xinzhan landslide in Tongzi County, China

The failure mechanism of Xinzhan landslide were investigated systematically based on multiple-integrated geotechniques, including field investigations, monitoring, and numerical simulations. Xinzhan landslide is a typical colluvial landslide, composed of gravelly soil in upper part and sandstone interbedded with mudstone in underlying part. The sliding surface is closing to the soil-rock interface with average depth about 8 m and the main sliding direction 287°. The occurrence of Xinzhan landslide is attributed to its unique geological environment and sustained rainfall. The hydro-mechanical coupling results indicate that under sustained rainfall, the rainwater infiltrates into gravelly soil, rising the pressure and forming transient saturation zone near the soil-rock interface, where the strength parameter is weakened under effect of water. As a consequence, the plastic deformation is intensified. Additionally, the deformation evolution trend of landslide under different rainfall intensities is also studied. The results show that the greater rainfall intensity, the shorter rainfall duration required for the landslide to produce accelerated deformation. The rainfall intensity-duration curve is used to construct the critical rainfall early warning criterion of Xinzhan landslide. The R2 of the fitting formula is 0.971, which indicates that the formula can effectively serve the early warning and provide convenience for highway safety construction.

Quantitative Analysis of the Effects of an Earthquake on Rainfall Thresholds for Triggering Debris-Flow Events

The impacts of destructive earthquakes on rainfall thresholds for triggering the debris flows have not yet been well investigated, due to lacks of data. In this study, we have collected the debris-flow records from the Wenchuan, Lushan, and Jiuzhaigou earthquake-affected areas in Sichuan Province, China. By using a meteorological dataset with 3 h and 0.1° resolutions, the dimensionless effective rainfall and rainfall intensity-duration relationships were calculated as the possible thresholds for triggering the debris flows. The pre- and post-seismic thresholds were compared to evaluate the impacts of the various intensities of earthquakes. Our results indicate that the post-quake thresholds are much smaller than the pre-seismic ones. The dimensionless effective rainfall shows the impacts of the Wenchuan, Lushan, and Jiuzhaigou earthquakes to be ca. 26, 27, and 16%, respectively. The Wenchuan earthquake has the most significant effect on lowering the rainfall intensity-duration curve. Rainfall threshold changes related to the moment magnitude and focal depth are discussed as well. Generally, this work may lead to an improved post-quake debris-flow warning strategy especially in sparsely instrumented regions.

Study on the Classification of Urban Waterlogging Rainstorms and Rainfall Thresholds in Cities Lacking Actual Data

Extreme rainfall is the main influencing factor of urban waterlogging. Different types of rainfall often have different characteristics of waterlogging. In order to establish a more accurate urban flood control system, it is necessary to classify waterlogging rainstorms and divide their thresholds. This study proposes a method for applying web crawlers to identify waterlogging rainfall in cities lacking waterlogging observation data and classifying them using the rainfall intensity–duration curves. By selecting appropriate duration thresholds and return period, waterlogging rainstorms are divided into rainfall intensity waterlogging (IW), rainfall amount of waterlogging (AW), combined waterlogging (CW) and no waterlogging (NW). In the application of Zhengzhou City, China, the urban flood control standard and the rainfall time distribution characteristics are used as the basis for the selection of the return period and duration thresholds, and the storm water management model (SWMM) is constructed to simulate the 4 kinds of rainfall characteristics of waterlogging, which is similar to actual situations. It proves that the method is suitable for the classification and thresholds division of different waterlogging rainfall in cities. The results show that the best duration thresholds in Zhengzhou are 20 min (M20) and 60 min (M60), and the best return period standard is 2 a. The thresholds for the 4 types of waterlogging rainstorm are: M20 ≥ 26.47 mm, M60 ≥ 43.80 mm, CW; M20 ≥ 26.47 mm, M60 < 43.80 mm, IW; M20 < 26.47 mm, M60 ≥ 43.80 mm, AW; M20 < 26.47 mm and M60 < 43.80 mm, No waterlogging.

Modelling catchment‐scale shallow landslide occurrence and sediment yield as a function of rainfall return period

AbstractA model‐based method is proposed for improving upon existing threshold relationships which define the rainfall conditions for triggering shallow landslides but do not allow the magnitude of landsliding (i.e. the number of landslides) to be determined. The SHETRAN catchment‐scale shallow landslide model is used to quantify the magnitude of landsliding as a function of rainfall return period, for focus sites of 180 and 45 km2 in the Italian Southern Alps and the central Spanish Pyrenees. Rainfall events with intensities of different return period are generated for a range of durations (1‐day to 5‐day) and applied to the model to give the number of landslides triggered and the resulting sediment yield for each event. For a given event duration, simulated numbers of landslides become progressively less sensitive to return period as return period increases. Similarly, for an event of given return period, landslide magnitude becomes less sensitive to event duration as duration increases. The temporal distribution of rainfall within an event is shown to have a significant impact on the number of landslides and the timing of their occurrence. The contribution of shallow landsliding to catchment sediment yield is similarly quantified as a function of the rainfall characteristics. Rainfall intensity–duration curves are presented which define different levels of landsliding magnitude and which advance our predictive capability beyond, but are generally consistent with, published threshold curves. The magnitude curves are relevant to the development of guidelines for landslide hazard assessment and forecasting. Copyright © 2011 John Wiley & Sons, Ltd.

Tillage-crop residue management and rainfall-runoff relationships for the Alemaya catchment in Eastern Ethiopia

A field study was conducted in the Alemaya catchment, Eastern Ethiopia, with the objective of determining the effect of tillage practices, crop reside cover and rainfall characteristics on runoff during two rainfall seasons on a clayey Regosol with 5% slope. Relationships between runoff and rainfall characteristics, such as the amount, intensity and erosivity were established from a two-year data set. The results on fields without crop showed that a minimum of 21 ha−1 of fresh wheat residue is required to reduce runoff from low intensity storms and 4 t ha−1 of residue for high intensity storms with peak intensities of more than 55 mm h−1. These norms can be used for estimating runoff under comparable soil and climatic conditions. A technique was also developed to estimate runoff from the rainfall intensity-duration curve and the mean soil infiltration rate.

Effect of maximum flood width on road drainage inlet spacing

Based on the kinematic wave theory, a method has been developed for the determination of road drainage inlet spacing under the continuous grade condition. The input data required are the allowable maximum flood with, the physical characteristics of the roadway, the empirical relationship between the maximum discharge and the intercepted flow, and the rainfall intensity-duration curve. By applying the method to a roadway with the standard drainage inlet used in Singapore, the effect of maximum flood width on the inlet spacing has been assessed. The assessment shows that for a given maximum flood width, the inlet spacing is wider for roads with steeper cross and longitudinal slopes. An increase in maximum flood width gives an exponential increase in inlet spacing.

Effect of maximum flood width on road drainage inlet spacing

Based on the kinematic wave theory, a method has been developed for the determination of road drainage inlet spacing under the continuous grade condition. The input data required are the allowable maximum flood width, the physical characteristics of the roadway, the empirical relationship between the maximum discharge and the intercepted flow, and the rainfall intensity-duration curve. By applying the method to a roadway with the standard drainage inlet used in Singapore, the effect of maximum flood width on the inlet spacing has been assessed. The assessment shows that for a given maximum flood width, the inlet spacing is wider for roads with steeper cross and longitudinal slopes. An increase in maximum flood width gives an exponential increase in inlet spacing.

Kinematic wave method for determination of road drainage inlet spacing

Based on the kinematic wave theory, which is shown to be generally applicable to road drainage situations, a method has been developed for the determination of road drainage inlet spacing under the continuous grade condition. The input data required are the allowable maximum flood width, the physical characteristics of the roadway, the empirical relationship between the maximum discharge and the intercepted flow, and the rainfall intensity—duration curve. Application of the method to the Singapore inlet condition shows that for a given maximum flood width, the inlet spacing varies with the cross and longitudinal slopes of the roadway. The spacing of inlets is wider for roads with steeper slopes.