Long-duration Rainfall Research Articles

Influence of rubber particle inputs on nitrogen removal efficiency of bioretention systems.

Bioretention systems effectively capture rubber particles and other microplastics in stormwater runoff. However, it is uncertain whether long-term particle accumulation affects pollutant removal efficacy. This study investigated the impact of various concentrations of ethylene-propylene-diene-monomer (EPDM) particles (0, 50, 100, and 400 mg/L) on bioretention system nitrogen removal performance. The input of EPDM during short-duration (2 h) rainfall favored the removal of nitrogen, and the total nitrogen effluent concentration of the bioretention system with EPDM was reduced by 0.59-1.52 mg/L compared with that of the system without EPDM. In addition, the input of EPDM reduced the negative effects of drought. During long-duration (24 h) rainfall, higher concentrations of EPDM led to lower nitrate-nitrogen concentrations in the effluent. The bioretention system with EPDM required less time for nitrate-nitrogen removal to reach 50% than that without EPDM input. Microbial community analysis showed that EPDM increased the relative total abundance of denitrifying bacteria (such as Dechloromonas, Zoogloea, Ramlibacter, and Aeromonas) by 7.25-10.26%, which improved the denitrification capacity of the system.

Madden Julian Oscillation Influence on Diurnal Variation of Rainfall in Mentawai Islands Indonesia from IMERG Observations

Abstract Mentawai is a small island located in the Indian Ocean, so its rainfall pattern tends to be different from the larger islands in Indonesian region. Various scales of factors influence this, one of which is Madden Julian Oscillation (MJO). The aim of this study is to determine effect of MJO in Mentawai Islands on the diurnal variation of rainfall. Rainfall data was collected from 2000-2022 from Integrated Multi-SatellitE Retrievals for GPM (IMERG). Diurnal variations were observed in the accumulation (PA), frequency (PF), and intensity (PI) of rainfall and MJO was classified into active phase (2, 3, 4, and 5) and inactive phase (1, 6, 7, and 8) during the seasonal period (DJF-MAM-JJA-SON). Diurnal peak times in PA, PF, and PI occur later when MJO is active than when MJO is inactive, especially in JJA and SON periods in Mentawai Islands and Mentawai Strait. When MJO is active, average PA and PF are higher than when MJO is inactive. The average of PI is higher around the ocean during active and inactive phases of MJO. The number of short-duration rainfall events occurred over the land, while long-duration rainfall occurred over the ocean.

Evaluating the Impacts of Fertilization and Rainfall on Multi-Form Phosphorus Losses from Agricultural Fields: A Case Study on the North China Plain

Excessive fertilizer application increases the risk of eutrophication and agricultural non-point source pollution (ANPS) in rivers near farmland. However, the processes and mechanisms of runoff and phosphorus losses, particularly in the interflow, under various fertilizer treatments and rainfall scenarios are not well understood. This study used orthogonal experimental methods to investigate the combined effects of fertilization schemes and rainfall intensity on multi-form phosphorus runoff losses and to establish statistical relationships and regression models between phosphorus losses and environmental factors in surface runoff and interflow. The results indicated that (1) the optimized fertilization scheme, compared with conventional fertilization, enhanced pak choi (Brassica rapa) growth while reducing phosphorus runoff losses. By reducing phosphorus fertilization by 35.7%, total phosphorus losses decreased by 29.3%, 34.2%, and 29.8% under light, moderate, and heavy rainfall, respectively. (2) Different fertilizer applications and rainfall intensities had varying effects on phosphorus losses through different pathways. Fertilizer application was the primary factor affecting phosphorus losses in surface runoff, while rainfall intensity mainly influenced phosphorus losses through interflow. (3) Surface runoff was the dominant pathway for phosphorus losses from farmland (>92.0%), with particulate phosphorus (>89.4%) being the predominant form. However, under high-intensity and long-duration rainfall, interflow became a significant pathway for phosphorus losses. This study highlights the importance of optimized fertilization in reducing phosphorus losses and improving fertilizer efficiency in agricultural fields. The findings will help develop strategies to mitigate ANPS and soil nutrient losses in the North China Plain.

Unique Seasonal Variation in Rainfall Diurnal Features on the Yunnan–Guizhou Plateau

Based on hourly precipitation observations, the diurnal variation in precipitation and its seasonal evolution over the Yunnan–Guizhou Plateau (YGP) were analyzed. The results indicate that the seasonal variation in hourly rainfall in the western part of the YGP is unique. The rainfall reaches its hourly maximum during the late afternoon in spring (March–April) and during nighttime in summer (July–August), which contrasts with the pattern in most of eastern China. By further classifying the rainfall into short-duration (1–3 h) and long-duration (more than 6 h) events, the unique seasonal variations in the western YGP are found to mainly be comprised of short-duration rainfall. The long-duration rainfall shares similar diurnal peaks year-round for both the western and eastern parts of the YGP. The short-duration rainfall in the western part of the YGP shows a year-round afternoon peak, which is different from that of the eastern YGP, which peaks from midnight to early morning in spring and in the late afternoon in summer. The surface maximum daily temperature and low-level instabilities reach their annual maximum in spring over the western YGP and are also higher than in other parts of the YGP, together providing favorable conditions for convection to be triggered in spring afternoons over the western YGP.

UAV, GNSS, and GIS for the Rapid Assessment of Multi-Occurrence Landslides

Intense long-duration rainfall or extreme precipitation in a few hours can provoke many simultaneous shallow landslides. In the past, the term multi-occurrence regional landslides (MORLEs) was proposed to describe such phenomena. In the current study, unmanned aerial vehicles in combination with a global navigation satellite system sensor and geographical information systems seem to be the ideal solution for the rapid assessment of many landslides occurring in Aitoloakarnania Prefecture, Western Greece. Fourteen landslides were accurately mapped within a few working days, and precise orthophotos and reports were created and submitted to the local authorities. The analysis of meteorological data proved that there is a peak in precipitation height that triggers the MORLEs in the specific area. Specifically, the value of the daily precipitation was defined at 80 mm.

Frequency analysis of extreme rainfall over the Japanese archipelago by leveraging gauge-adjusted radar and satellite estimates

With the increasing frequency of extreme rainfall and difficulty in capturing their spatial variability by rain gauges, especially over regions with complex topographic and climatic features like Japan, there is a growing interest in using radar and satellite-derived precipitation estimates for building intensity–duration–frequency (IDF) curves. Such a statistical method provides references for studying extreme rainfall statistics at varying spatiotemporal scales. Yet, a comparative evaluation of the efficiency of these datasets to derive reliable IDFs over the Japanese archipelago is lacking. This study compares IDFs developed from four rain gauge-adjusted remotely sensed datasets (RSDs) derived from weather radars (R/A) and satellites (GsMAP_G, CMORPH_G, and IMERG_G) with those created from long-term rain gauge records (i.e., reference IDFs) for evaluating their reliabilities, particularly for 10- and 100-year return periods. A Bayesian Generalized Extreme Value model was adopted to estimate the IDFs. The results show that the four RSDs exhibited varying performances in deriving reliable IDFs within the 5–95% confidence bounds of the reference IDFs depending on rainfall duration and climate settings. While R/A performed better for one-hour rainfall return levels, particularly in the cold climate with warm summers, satellite-driven RSDs, especially IMERG_G, showed better performances for long-duration rainfall return levels. The performance discrepancies were primarily linked to the differences in rainfall estimation and bias adjustment schemes rather than the differences in record lengths and spatial resolutions among the tested RSDs. Thus, it is crucial to consider the rainfall duration and climate settings when using the derived IDFs for diverse practical applications.

Temporal and spatial variation of typhoon-induced surges and the impact of rainfall in a tidal river

The Huangpu River, which flows into the Yangtze Estuary, runs through Shanghai Municipality in China. During the flood season, typhoon-induced surges result in extremely high water levels in the Huangpu River, which is the main factor threatening flood control safety in Shanghai. Based on observations of water levels at three stations along the Huangpu River from 2008 to 2021, together with wind and rainfall, this paper investigates: the trends of the annual highest storm surges; the differences in periodic variation and magnitude of surges during the spring-neap cycle; the longitudinal variation of surges; and the impact of rainfall. The results show that the annual highest surges at three stations all show a significant increasing trend, which is caused by the increasing wind speed, and the intensity and duration of rainfall during typhoon events, induced by the increasing frequency of landfall and close-to-YE (Yangtze Estuary) typhoon events, and strong and very strong typhoon events. The periodic variation and magnitude of surges show clear differences during the spring-neap cycle, resulting from the largest nonlinear surge-tide interaction during spring tide and the smallest during neap tide. Heavy rainfall can reduce the probability of 6–7 h and 2.7–3.3 h periods, and change the phase of the periodic variation, inducing partial main peaks and maximum surges during ebb or low tide. The longitudinal variation of storm surge along the Huangpu River can be divided into three types: decreasing upstream, first increasing then decreasing, and increasing upstream. Heavy and long-duration rainfall increases the water discharge from the basin to the river, amplifying the surge, with the largest impact in the upper reach and the smallest in the lower reach, which is the main factor inducing the latter two types, particularly the third type.

Roles of soil surface roughness in surface–subsurface flow regulation and sediment sorting

Tillage-induced soil surface roughness (SSR) and rainfall interactions determine the process of water erosion. In this study, long-duration rainfall simulations were conducted to investigate the effect of SSR on the processes of surface–subsurface flow generation and soil loss, flow hydrodynamics, sediment sorting and transport on the steep red soil sloping farmland, southern China. Rainfalls with intensities of 30, 60, and 90 mm h−1 with duration of 180 min were applied to two soil surfaces (smooth and rough) with the slope gradient of 15°. Lesser surface flow and more subsurface flow were generated on the rough surface, which also accelerated the initial flow response and erosion stage advancement. The reduction effect of SSR on the sediment yield was significant under light rain or in the sheet erosion stage, while was limited when the rainfall intensity became stronger or entering the rill erosion stage. Differences in the spatial variability of soil crusts and the spatial distribution of rill networks were the main agents. Stream power took roughness factor into consideration well, thus was identified as the best hydraulic parameter for the prediction of soil loss rate. The investigation of particle size distribution of the eroded sediment showed the contents of sand, silt and clay changed from 15.9%, 64.9%, and 19.2% (average value of the original soil) to 22.9%, 53.1%, and 24% for the smooth surface, and to 37.8%, 42.1%, and 20.2% for the rough surface (average value of the eroded sediment). The selective and degrading effects of SSR on sediment particles were represented well. The rough surface was more inclined to transport clay particles than the smooth surface in the former period of erosion. Sand particles instead become more enriched with the extension of rainfall time. The results are beneficial for controlling the water erosion on agricultural sloping farmland.

Numerical analysis of the impacts of rainfall on permafrost-related slope stability on the Qinghai–Tibet Plateau

Study regionThis study interrogates a landslide in ice-rich permafrost region in the Eastern Qinghai–Tibet Plateau, China. Study focusClimate warming has increased the frequency and intensity of rainfall events, changing hydrothermal processes and the soil mechanical properties, thus affecting slope stability in permafrost region. The purpose of this paper is to elucidate the variations in soil volumetric water content (VWC) which may influence the mechanical properties of unstable slopes in ice-rich permafrost region under different rainfall conditions. New hydrological insights for the regionThis paper integrates the rainfall infiltration boundary conditions and Mohr–Coulomb criterion into a thermo–hydro–mechanical (THM) model and analyzes a landslide case in the permafrost regions. The results show that the THM model can effectively account for the impacts of VWC variation under different rainfall conditions. The influence of rainfall on the VWC diminishes as depth increases, with a more pronounced effect observed at depths less than 1 m. At depths exceeding 1 m, the impact is relatively minor. Under the condition of low-intensity, long-duration rainfall, with accumulated precipitation exceeding 60 mm, the cohesion and internal friction angle decrease to 4.2kPa and 8.1°, respectively, with a deep-layer integral slippage. In contrast, under the condition of high-intensity, short-term rainfall, the accumulated rainfall exceeds 75 mm and the internal friction angle decreases from 39° to 26°, with shallow-layer slippage. The results add on to our understanding engineering problems and periglacial geomorphic processes under the influence of climate warming.

Trends in soil frost formation in a warming maritime climate and the impacts on urban flood risk

The most severe urban flooding in cold maritime climates is due to the co-action of long-duration rainfall, snowmelt, and soil frost. Increasing winter air temperature due to climate change is projected to change the magnitude and frequency of rain-on-snow (RoS) events and increase the number of freeze–thaw cycles and midwinter snowmelt. While daily rainfall records are readily available, less is known about the infiltration and frost formation within urban soils. Thus, there is uncertainty on how warming winter conditions may affect urban flood risk and the climate resilience of cities. The aim of this study was, therefore, to assess soil frost formation in the past 70 years in the maritime city of Reykjavík, Iceland (64° N, 21° W), and its co-action with runoff generation, and the potential implications on urban flood risk. To that end, the daily thermal and hydraulic conditions of the soil were simulated using the Simultaneous Heat and Water (SHAW) model dating back to 1949, calibrated based on hourly observations from 2007. Model simulations indicated that the minimum soil temperature at 10 cm depth has been warming at a rate of 0.015 °C/year in the past seven decades. Climate warming is also noted in a steady decline in frost depth and the duration of soil frost each winter (p-value < 0.05). However, the freezing season has shortened so that the timing of maximum frost coincides more with the timing of maximum RoS and snowmelt events. Furthermore, RoS events during frost have the capacity to produce larger runoff volumes than rainfall or snowmelt alone based on the joint frequency analysis of winter events using the copula method. This, combined with increasing volume during RoS events, suggests that winter floods may intensify in the next decades, which urges re-thinking urban stormwater management in cold climates.

Characteristic of rain rate associated with floods during the 2021 rainy season around Jakarta and Bekasi River

The Megacity Jakarta has encountered serious floods associated with high intensity but a short-duration rainfall or low intensity with a long-duration rainfall. During the rainy season, on 4 Feb 2021, Jakarta was inundated as rainfall intensity increased. However, little is known about the meteorological factors that might contribute to this heavy rainfall. In this study, we used the 6-min X-Band Doppler radar, one-hour satellite and reanalysis data to understand the spatial distribution of rainfall and explore the background conditions that might influence the enhanced rainfall over Jakarta and Bekasi River. Other than previous studies, we found that over Jakarta, the areas receiving high rainfall are more widespread and further to the northeast ocean with an intensity of above 4.5 mm h-1. High intensity of rainfall starts to develop in the afternoon over the inland areas at around 08-10Z (3.00-5.00 PM). Background condition shows a strong westerly wind speed crossing over Java Island, and this might initiate the development of rainfall over the region.

Experiment Study of Porous Fiber Material on Infiltration and Runoff of Winter Wheat Farmland in Huaibei Plain, China

Drought and floods frequently occurred in the Huaibei plain, which was the main factor that restricted agricultural development. We conducted rainfall experiments, which aimed to explore the impacts of porous fiber material (PFM) on the farmland water cycle processes and soil water storage capacity. In this study, we designed two types of rainfall intensities, 4 PFM volumes, 4 growth periods of winter wheat, and a total of 8 experimental groups and 32 rainfall events to evaluate the effects. The result showed that PFM had significantly affected the soil water circulation in the grain-filling period, and the peak flow and runoff decreased maximumly compared with other periods. However, the effect of PFM on surface runoff was slighter in the fallow period, and the peak flow or runoff decreased with the PFM volumes increased (R2 = −0.92, −0.99). In the 100 and 50 mm/h rainfall intensities, PFM decreased the average values of runoff by (55.2–59.6%) and (57.2–90.2%), reduced peak flow by (62.2–68%) and (64.2–86%), and increased the stable infiltration rate by (13.4–14.3%) and (26.6–41.3%), respectively. After the rainfall experiments ended for 1 h, the surface soil water rapidly infiltrated into PFM, which made the water-storage capacity of PFM groups higher than the control groups by 0.2–11% Vol. Subsequently, PFM increased the water-holding capacity by 0.3–2.3% Vol in the 10–70 cm depth from the heading period to the fallow period. It had a positive relationship between the PFM volumes and the average values of soil water content (R2 = 0.8, 0.84). In general, PFM could increase infiltration, reduce runoff, and improve the water-storage capacity to alleviate soil water deficit and the risk of farmland drought and floods. It has an excellent application effect in long-duration rainfall.

Temporal changes in rainfall intensity–duration thresholds for post-wildfire flash floods in southern California

Abstract. Rainfall intensity–duration (ID) thresholds are commonly used to assess flash flood potential downstream of burned watersheds. High-intensity and/or long-duration rainfall is required to generate flash floods as landscapes recover from fire, but there is little guidance on how thresholds change as a function of time since fire. Here, we force a hydrological model with radar-derived precipitation to estimate ID thresholds for post-fire flash floods in a 41.5 km2 watershed in southern California, USA. Prior work in this study area constrains temporal changes in hydrological model parameters, allowing us to estimate temporal changes in ID thresholds. The results indicate that ID thresholds increase by more than a factor of 2 from post-fire year 1 to post-fire year 5. Thresholds based on averaging rainfall intensity over durations of 15–60 min perform better than those that average rainfall intensity over shorter time intervals. Moreover, thresholds based on the 75th percentile of radar-derived rainfall intensity over the watershed perform better than thresholds based on the 25th or 50th percentile of rainfall intensity. Results demonstrate how hydrological models can be used to estimate changes in ID thresholds following disturbance and provide guidance on the rainfall metrics that are best suited for predicting post-fire flash floods.

Evolution of Erosion Morphology Changes Subsequent Erosion Process on Granite Red Soil Slope During Long-Duration Rainfall

Evolution of Erosion Morphology Changes Subsequent Erosion Process on Granite Red Soil Slope During Long-Duration Rainfall

Analysis and influence of rainfall infiltration of ancient city wall based on in-situ monitoring：a case study of The XingChun gate Lishui Prefecture

Rainfall infiltration is an important factor affecting the stability of the ancient city wall. To state the wall line spring door where, for example, soil temperature and humidity sensor, the earth pressure meter and rain gauge carried out such as rainfall, volume moisture content and soil pressure monitoring, analyzed the inner core wall soil volume moisture content and soil pressure response law of rainfall different rainfall conditions is studied through numerical simulation method the stability of the ancient city wall. The results show that :(1) rainfall has a significant effect on the volume moisture content and earth pressure of the inner core soil;(2) The response to rainfall is different at different depths of the city wall, and the response to rainfall in the middle part of the city wall has a certain hysteresis;(3) Compared with the low-intensity and long-duration rainfall, the high-intensity and short-duration rainfall has a greater impact on the stability of the city wall. The research results have certain guiding significance for the protection and monitoring of the ancient city wall.

桂西北喀斯特小流域降雨稳定氢氧同位素组成及影响因素

气候变化背景下，降雨稳定氢氧同位素的变化对以快速的地表-地下水文过程为主要特征的喀斯特生态水文研究有重要意义。以桂西北典型喀斯特峰丛洼地小流域为研究对象，测定2013年至2018年日尺度及2019年至2020年8场大雨或特大暴雨的雨水稳定氢氧同位素组成，分析降雨稳定氢氧同位素变化特征及其影响因素。结果表明，研究区夏半年以海洋性水汽为主，冬半年以干燥的大陆性气团为主，导致夏半年降水δD、δ¹⁸O和氘盈余值显著（P<0.05）低于冬半年。降水的稳定氢氧同位素存在显著的反温度效应和雨量效应，即δ¹⁸O值与温度呈显著（P<0.001）负相关，与降雨量呈显著（P<0.001）正相关。次降雨过程中，持续时间较长（>9.5 h）的降雨存在显著的（P<0.05）雨量效应，特大暴雨则不存在雨量效应，与大气或地理因素有关。研究区水汽来源及降水强度存在明显的时间差异，因此在开展喀斯特小流域生态水文过程研究时，需要关注降水稳定氢氧同位素组成在不同时间尺度上的变化特征。;In the context of global climate change, the variation of stable hydrogen and oxygen isotopes during rainfall is of great significance to study of the rapid surface-to-subsurface hydrologic processes in karst areas. We measured the hydrogen-oxygen isotope composition of water samples during the inter-annual scale rainfall from 2013 to 2018 and eight typical rainfalls (heavy rain to extremely heavy rain) from 2019 to 2020 in the karst area of northwest Guangxi. We also analyzed the variation characteristics of hydrogen-oxygen isotope and its influencing factors. The results show that the δD, δ¹⁸O, and d-excess in the summer half-year is significant (P<0.05) lower than the winter half-year. Hydrogen and oxygen isotopes stable in precipitation have anti-temperature effect and rainfall effect, that is, δ¹⁸O value has a significantly (P<0.001) negative linear relationship with temperature and a significantly (P<0.001) positive linear relationship with rainfall. In the process of rainfall, the rainfall effect was only observed in the long-duration (> 9.5 h) rainfall events. Extremely heavy rain does not have a rainfall effect and is related to atmospheric or geographical factors. These results suggest that studies on eco-hydrological processes should focus on the various characteristics of stable hydrogen and oxygen isotopic compositions of precipitation at different time scales.

Developing Green Infrastructure Strategies Based on the Analysis of Sewer System Critical Components

Flooding has presented a significant risk for urban areas around the world. Road inundation is one of the severe consequences leading to traffic issues and congestion. Green infrastructure (GI) offers further potential for stormwater management as an environmentally friendly and sustainable solution. However, sewer system behaviour has been overlooked in GI implementation. This study investigates sewer performance by measuring topological connectivity and hydraulic characteristics, and critical components are identified under different design storms. Three retrofit scenarios, including enlarged pipes (grey infrastructure, Grey I), rain gardens (GI), and the combination of enlarged pipes and increased rain gardens (GI + Grey I), are proposed according to the distribution of critical components. The results show that it is feasible to locate the vulnerable parts of the sewer system and GI site allocations based on the critical components that significantly impact the performance of the entire system. While all three scenarios can mitigate inundation, GI and GI + Grey I perform better than pipe enlargement, especially for runoff reduction during long-duration rainfall. Furthermore, the sewer behaviour and retrofit effect are dynamic under different rainfall patterns, leading to diverse combined effects. The discoveries reveal that the adaptation measures should combine with sewer behaviour and local rainfall characteristics to enhance stormwater management.

Characteristics of the Precipitation Diurnal Variation and Underlying Mechanisms Over Jiangsu, Eastern China, During Warm Season

Based on the hourly precipitation observed from ∼1800 automatic rain gauges during 2013–2017, characteristics of precipitation diurnal variation and underlying mechanisms over Jiangsu Province, eastern China, during the warm season (May to September) have been revealed in this study. Results show that the precipitation amount (PA), frequency (PF), and intensity (PI) are zonally distributed over Jiangsu. The precipitation shows distinct diurnal cycle and zonal distribution. The large precipitation is located over the southwest side of the Jiangsu section of Yangtze River (JSYR). From midnight to noon, the precipitation expands northeastward, but the precipitation shrinks southeastward from noon to midnight. Meanwhile, the PA is larger during the daytime than that during the nighttime over most Jiangsu. In addition, the PA shows two diurnal peaks, with one in the early morning mainly resulting from the long-duration rainfall and the other in the afternoon resulting from the short-duration rainfall. The total rainfall is largely contributed by the long-duration rainfall. During the whole warm season, water vapor convergence (divergence) and ascending (sinking) movements are consistent, corresponding to the long-duration precipitation diurnal cycles. The contribution of rainfall with long (short) duration to the total rainfall over most areas shows very distinct sub-seasonal variations with a clear decreasing (increasing) trend from pre-Meiyu through Meiyu to post-Meiyu. Among the three subperiods in a warm season, the PA and diurnal cycle of the total rainfall are mostly contributed by those during the Meiyu period. The long-duration precipitation is closely related to the enhancement of the water vapor convergence during the pre-Meiyu period. However, during the Meiyu and post-Meiyu periods, the long-duration precipitation is more consistent with the dynamic lift since the water vapor is abundant. Concluded from the cluster analysis, precipitation spatial distributions are closely associated with the underlying surface, such as the Yangtze River, big cities, Lake Taihu, Lake Hongze, and complex coastal lines. The diurnal variation of the rainfall over different underlying surfaces shows respective diurnal cycle features.

Identifying optimal ridge practices under different rainfall types on runoff and soil loss from sloping farmland in a humid subtropical region of Southern China

The relationship between different rainfall types, different soil management practices, and soil erosion is not yet fully understood. In-situ observations of soil and water loss on sloping farmland in the red soil region of southern China with a subtropical monsoon environment were taken at 12 runoff plots with four treatments, i.e, downslope ridges, downslope ridges with hedgerow intercropping, contour ridges, and bare flat land as control, over a seven-year period from 2012 to 2018. During this time, 253 natural rainfall events were classified into three rainfall types by K-means clustering according to the rainfall depth, maximum-30 min rainfall intensity and rainfall duration, and surface runoff and soil erosion processes in relation to the rainfall types under different ridge practices were analyzed. The results show that water-induced soil erosion on the flat land control was significant, with average annual soil loss of 76.73 t·ha−1·yr−1, reaching the “intense erosion” classification, and ridge practices were confirmed to reduce annual runoff and soil loss in all rainfall events by 18.9–62.0% and 68.9–86.3%, respectively. On the whole, rainfall events can be divided into three types: intense, normal, and long-duration. Among them, intense and normal rainfall cause the majority of soil (88.5–93.7%) and water (75.0–83.8%) loss in this area, but the efficiencies in runoff and soil reduction during long-duration rainfall events were the lowest, or even negative on farmlands with only downslope ridges. 20% of the total rainfall events, in which 84.3–92.2% were intense and normal rainfall events, contributed to 29–33% of the total rainfall depth, 68–89% of the total runoff depth, and 94–98% of the total soil loss. Rainfall depth played a dominant role in generating runoff, while runoff accumulation was a main factor influencing on soil loss. Findings from our study indicate that by choosing a more appropriate ridge practice according to different rainfall types, there can be a positive effect on soil and water conservation.

Capability of LISEM to estimate flood hydrographs in a watershed with predominance of long-duration rainfall events

Capability of LISEM to estimate flood hydrographs in a watershed with predominance of long-duration rainfall events