Individual Rainfall Change Based on Observed Hourly Precipitation Records on the Chinese Loess Plateau from 1983 to 2012

The magnitude and spatiotemporal distribution of precipitation are the main drivers of hydrologic and agricultural processes in soil moisture, runoff generation, soil erosion, vegetation growth and agriculture activities on the Loess Plateau (LP). This study detects the spatiotemporal variations of individual rainfall events during a rainy season (RS) from May to September based on the hourly precipitation data measured at 87 stations on the LP from 1983 to 2012. The incidence and contribution rates were calculated for all classes of rainfall duration and intensity to identify the dominant contribution to the rainfall amount and frequency variations. The trend rates of regional mean annual total rainfall amount (ATR) and annual mean rainfall intensity (ARI) were 0.43 mm/year and 0.002 mm/h/year in the RS for 1983–2012, respectively. However, the regional mean annual total rainfall frequency (ARF) and rainfall events (ATE) were −0.27 h/year and −0.11 times/year, respectively. In terms of spatial patterns, an increase in ATR appeared in most areas except for the southwest, while the ARI increased throughout the study region, with particularly higher values in the northwest and southeast. Areas of decreasing ARF occurred mainly in the northwest and central south of the LP, while ATE was found in most areas except for the northeast. Short-duration (≤6 h) and light rainfall events occurred mostly on the LP, accounting for 69.89% and 72.48% of total rainfall events, respectively. Long-duration (≥7 h) and moderate rainfall events contributed to the total rainfall amount by 70.64% and 66.73% of the total rainfall amount, respectively. Rainfall frequency contributed the most to the variations of rainfall amount for light and moderate rainfall events, while rainfall intensity played an important role in heavy rainfall and rainstorms. The variation in rainfall frequency for moderate rainfall, heavy rainfall, and rainstorms is mainly affected by rainfall duration, while rainfall event was identified as a critical factor for light rainfall. The characteristics in rainfall variations on the Loess Plateau revealed in this study can provide useful information for sustainable water resources management and plans.

Download Full-text

Estimating Raindrop Kinetic Energy: Evaluation of a Low-Cost Method

Applied Engineering in Agriculture ◽

10.13031/aea.11518 ◽

2017 ◽

Vol 33 (4) ◽

pp. 551-558 ◽

Cited By ~ 2

Author(s):

Jian Wang ◽

Dexter B. Watts ◽

Qinqian Meng ◽

Thomas R. Way ◽

Qingfeng Zhang

Keyword(s):

Soil Erosion ◽

Kinetic Energy ◽

Loess Plateau ◽

Filter Paper ◽

Rainfall Intensity ◽

Low Cost ◽

Rotating Disks ◽

The Loess Plateau ◽

Rainfall Events ◽

Raindrop Impact

Abstract. The Loess Plateau of China is regarded as the most intensively eroded region in the world and soil erosion caused by raindrop impact is a common occurrence on agricultural land within this region. Therefore, understanding the influence of rainfall energy on the soil surface is needed to improve prescriptions for best management practices aimed at mitigating erosion. Disdrometers for measuring rainfall energy are presently available; however, these are relatively expensive and their use may not be justified for determining raindrop energy for predictive soil erosion models in regions where there are limited economic resources. To overcome this constraint, a device was tested for evaluating size and velocity of water drops during rainfall events. This device utilized two rotating disks combined with filter paper to obtain raindrop diameter and velocity which can then be used for determining the kinetic energy of falling raindrops. With this device, raindrop diameter was determined from the resultant raindrop stain left on the filter paper during rainfall events and velocity was calculated from the time it took a falling raindrop to travel between the pair of rotating disks. Measurements were taken for approximately 10 minutes during each of six rainfall events of different intensities over a three month period (from June to August of 2013). The smallest raindrop measured was 0.39 mm diameter and the largest was 5.92 mm diameter. The event average raindrop diameter increased with increasing event rainfall intensity. The minimum raindrop impact velocity was 1.47 m s-1, the maximum was 9.45 m s-1, and the event average terminal velocity increased as event rainfall intensity increased. Estimated raindrop kinetic energy ranged from 0.04 × 10-6 J to 4728.21 × 10-6 J, with event mean raindrop kinetic energy ranging from 40.33 x 10-6 J to 276.94 × 10-6 J. The relationship between estimated event rainfall kinetic energy and event rainfall intensity was represented by an exponential function. The disk device was also compared to an optical disdrometer. The data collected for rainfall intensity, raindrop diameter, and velocity were statistically similar between the two devices. Results from this study show that this low-cost method can be used to estimate rainfall kinetic energy in the Loess Plateau region of Northwest China. Keywords: Loess Plateau, Raindrop diameter, Raindrop velocity, Rainfall intensity.

Download Full-text

Effect of Multicollinearity on the Bivariate Frequency Analysis of Annual Maximum Rainfall Events

Water ◽

10.3390/w11050905 ◽

2019 ◽

Vol 11 (5) ◽

pp. 905 ◽

Cited By ~ 2

Author(s):

Yoo ◽

Cho

Keyword(s):

Frequency Analysis ◽

Rainfall Intensity ◽

Rainfall Event ◽

Total Rainfall ◽

Maximum Rainfall ◽

Rainfall Events ◽

Rainfall Duration ◽

Rainfall Depth ◽

The Mean ◽

Annual Maximum Rainfall

A rainfall event, simplified by a rectangular pulse, is defined by three components: the rainfall duration, the total rainfall depth, and mean rainfall intensity. However, as the mean rainfall intensity can be calculated by the total rainfall depth divided by the rainfall duration, any two components can fully define the rainfall event (i.e., one component must be redundant). The frequency analysis of a rainfall event also considers just two components selected rather arbitrarily out of these three components. However, this study argues that the two components should be selected properly or the result of frequency analysis can be significantly biased. This study fully discusses this selection problem with the annual maximum rainfall events from Seoul, Korea. In fact, this issue is closely related with the multicollinearity in the multivariate regression analysis, which indicates that as interdependency among variables grows the variance of the regression coefficient also increases to result in the low quality of resulting estimate. The findings of this study are summarized as follows: (1) The results of frequency analysis are totally different according to the selected two variables out of three. (2) Among three results, the result considering the total rainfall depth and the mean rainfall intensity is found to be the most reasonable. (3) This result is fully supported by the multicollinearity issue among the correlated variables. The rainfall duration should be excluded in the frequency analysis of a rainfall event as its variance inflation factor is very high.

Download Full-text

Prediction of factors affecting activation of soil erosion by mathematical modeling at pedon scale under laboratory conditions

Scientific Reports ◽

10.1038/s41598-020-76926-1 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Saeed Shojaei ◽

Zahra Kalantari ◽

Jesús Rodrigo-Comino

Keyword(s):

Soil Loss ◽

Rainfall Intensity ◽

Quadratic Function ◽

Interactive Effects ◽

Soil Protection ◽

Single Factor ◽

Rainfall Events ◽

Rainfall Duration ◽

The Impact ◽

Runoff Production

AbstractSoil degradation due to erosion is a significant worldwide problem at different spatial (from pedon to watershed) and temporal scales. All stages and factors in the erosion process must be detected and evaluated to reduce this environmental issue and protect existing fertile soils and natural ecosystems. Laboratory studies using rainfall simulators allow single factors and interactive effects to be investigated under controlled conditions during extreme rainfall events. In this study, three main factors (rainfall intensity, inclination, and rainfall duration) were assessed to obtain empirical data for modeling water erosion during single rainfall events. Each factor was divided into three levels (− 1, 0, + 1), which were applied in different combinations using a rainfall simulator on beds (6 × 1 m) filled with soil from a study plot located in the arid Sistan region, Iran. The rainfall duration levels tested were 3, 5, and 7 min, the rainfall intensity levels were 30, 60, and 90 mm/h, and the inclination levels were 5, 15, and 25%. The results showed that the highest rainfall intensity tested (90 mm/h) for the longest duration (7 min) caused the highest runoff (62 mm3/s) and soil loss (1580 g/m2/h). Based on the empirical results, a quadratic function was the best mathematical model (R2 = 0.90) for predicting runoff (Q) and soil loss. Single-factor analysis revealed that rainfall intensity was more influential for runoff production than changes in time and inclination, while rainfall duration was the most influential single factor for soil loss. Modeling and three-dimensional depictions of the data revealed that sediment production was high and runoff production lower at the beginning of the experiment, but this trend was reversed over time as the soil became saturated. These results indicate that avoiding the initial stage of erosion is critical, so all soil protection measures should be taken to reduce the impact at this stage. The final stages of erosion appeared too complicated to be modeled, because different factors showed differing effects on erosion.

Download Full-text

Evaluation of Rainfall Forecasts with Heavy Rain Types in the High-Resolution Unified Model over South Korea

Weather and Forecasting ◽

10.1175/waf-d-18-0140.1 ◽

2019 ◽

Vol 34 (5) ◽

pp. 1277-1293 ◽

Cited By ~ 4

Author(s):

Hwan-Jin Song ◽

Byunghwan Lim ◽

Sangwon Joo

Keyword(s):

High Resolution ◽

South Korea ◽

Korean Peninsula ◽

Heavy Rainfall ◽

Rainfall Intensity ◽

Heavy Rain ◽

Unified Model ◽

Moderate Intensity ◽

Local Data ◽

Total Rainfall

Abstract Heavy rainfall events account for most socioeconomic damages caused by natural disasters in South Korea. However, the microphysical understanding of heavy rain is still lacking, leading to uncertainties in quantitative rainfall prediction. This study is aimed at evaluating rainfall forecasts in the Local Data Assimilation and Prediction System (LDAPS), a high-resolution configuration of the Unified Model over the Korean Peninsula. The rainfall of LDAPS forecasts was evaluated with observations based on two types of heavy rain events classified from K-means clustering for the relationship between surface rainfall intensity and cloud-top height. LDAPS forecasts were characterized by more heavy rain cases with high cloud-top heights (cold-type heavy rain) in contrast to observations showing frequent moderate-intensity rain systems with relatively lower cloud-top heights (warm-type heavy rain) over South Korea. The observed cold-type and warm-type events accounted for 32.7% and 67.3% of total rainfall, whereas LDAPS forecasts accounted for 65.3% and 34.7%, respectively. This indicates severe overestimation and underestimation of total rainfall for the cold-type and warm-type forecast events, respectively. The overestimation of cold-type heavy rainfall was mainly due to its frequent occurrence, whereas the underestimation of warm-type heavy rainfall was affected by both its low occurrence and weak intensity. The rainfall forecast skill for the warm-type events was much lower than for the cold-type events, due to the lower rainfall intensity and smaller rain area of the warm-type. Therefore, cloud parameterizations for warm-type heavy rain should be improved to enhance rainfall forecasts over the Korean Peninsula.

Download Full-text

The Thresholds of Sediment-Generating Rainfall from Hillslope to Watershed Scales in the Loess Plateau, China

Water ◽

10.3390/w11112392 ◽

2019 ◽

Vol 11 (11) ◽

pp. 2392

Author(s):

Liang ◽

Jiao ◽

Dang ◽

Cao

Keyword(s):

Loess Plateau ◽

Sediment Yield ◽

Spatial Scales ◽

Water Erosion ◽

Rainfall Amount ◽

Rainfall Erosivity ◽

Watershed Scale ◽

The Loess Plateau ◽

Erosive Rainfall ◽

Hillslope Scale

Obtaining practical thresholds for erosive rainfall plays a crucial role in calculating rainfall erosivity and predicting water erosion. Nevertheless, the study of thresholds on subwatershed and watershed scales remains scarce. Given this, we presented the critical rainfall that generated the outflows of subwatersheds and watersheds as the threshold of sediment-generating rainfall. On the basis of the observation of twelve nested topographical units at the Peijiamaogou watershed in the Loess Plateau of China, we fitted regression relationships between rainfall indexes (rainfall amount, maximum 30-min intensity, maximum 60-min intensity, rainfall amount multiply maximum 30-min intensity, and rainfall amount multiply maximum 60-min intensity) and the proportion of cumulative sediment yield to the total sediment yield. We determined the thresholds of sediment-generating rainfall and explored the variabilities of thresholds across different spatial scales. Moreover, the covering area proportion (CAP) with rainfall indexes higher than the thresholds was also employed as thresholds at the subwatershed and watershed scales. The thresholds of CAP for P and I30 were 50.5% and 47.6% at the subwatershed scale, while 31.0% and 30.3% at the watershed scale. The thresholds of P and I30 at the subwatershed scale were higher than those of hillslope scale, while the threshold of I30 at the watershed scale was smaller compared to the other scales. In general, I30 was viewed as the best threshold among single rainfall indexes across different spatial scales, while P was not recommended as a practical threshold. This study can improve the prediction accuracy of water erosion across different spatial scales and develop the spatial scale effect of sediment yield in the loess hilly areas.

Download Full-text

The Geo-Hazards Triggered of Serial Reclamation Land of Extreme Precipitation in Typical Regions of the Loess Plateau

10.5194/egusphere-egu2020-16059 ◽

2020 ◽

Author(s):

Zhe Gao

Keyword(s):

Loess Plateau ◽

Water Conservation ◽

Rainfall Intensity ◽

Soil And Water Conservation ◽

Land Consolidation ◽

Geological Hazards ◽

The Loess Plateau ◽

The World ◽

Soil And Water ◽

Land Consolidation Project

The Geo-Hazards Triggered of Serial Reclamation Land of Extreme Precipitation in Typical Regions of the Loess Plateau Gao Zhe1,Zhang Genguang 1*,Gao Jian'en1,2,3,Li Xingyao1,Han Jianqiao2,3,Kang Youcai3,Guo Zihao3,Long Shaobo2,Dou Shaohui2,Zhang Yuanyuan3 1. College of Water Resources and Architectural Engineering, Northwest A&F University, 712100, Yangling, Shaanxi, China; 2. Institute of Soil and Water Conservation, Northwest A&F University, 712100, Yangling, Shaanxi, China; 3. Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, 712100, Yangling, Shaanxi, China;The &#8220;Gully Land Consolidation Project&#8221;(GLCP) was widely carried out all over the world, such as Spain, the United States and China. It was a new attempt to solve the shortage of regional land resources. Aiming at the problem that the influence of extreme rainstorms on the &#8220;Gully Land Consolidation Project&#8221;(GLCP) on the Loess Plateau.By using the method of actual measurement and analysis of categorical data, the erosion disaster in July 26 2017 was investigated in Niu Xue Gully of Wuding River Watershed in Zizhou County of the Central part of the Loess Plateau. The results showed :&#160;(1) The Niu Xue Gully Small Watershed in Zizhou County (109&#176;55'25"E, 37&#176;39'46"N), which was located in the central part of the Loess Plateau and belonged to the northern Shaanxi Loess Hilly-Gully region. The Niu Xuegou catchment covered an area of 0.48 km2 and the average altitude of the region in about 1000-1200 meters, land consolidation in the basin about 38 mu&#65288;25333.3m2&#65289;since 2014.(2) This storm was characterized by "long duration and large precipitation", the accumulated rainfall was 147.9 mm, the average rainfall intensity was 13.45 mm/h, the maximum rainfall intensity was close to 5 mm/min, the maximum flood peak discharge was 44.64 m3/s, the flood duration was about 11 hours, and the flood recurrence period was more than once in a hundred years.(3) The storm caused nearly a thousand geological hazards at the channel of the basin. The main types of disasters were as follows, gravity erosion types, such as landslides, landslides, and mudflows, account for 14.85% of the conventional geological hazards; secondary disasters of water erosion types, such as trench erosion and dam erosion, occurring at different locations on the slope, accounted for 51.05% and composite new-derived land destruction and dam break disasters account for nearly 10% .(4) The damage of cascade land preparation was closely related to the average flood discharge, embankment height and ecological vegetation cover in the watershed. The investigation provided technical support for the consolidation of the Chinese implementation of the "Cropland to Forest (Grass)" results on the Loess Plateau, and also provided theoretical support for the safe implementation of the &#8220;Gully Land Consolidation Project&#8221;(GLCP) around the world. Keywords: The loess plateau; Extreme rainstorm;The &#8220;Gully Land Consolidation Project&#8221;(GLCP)Funding:(National Key R&D Program of China: 2017YFC0504703)&#65307;(National Natural Science Foundation of China,41877078,41371276,51879227);(Research and Development and Integrated demonstration of key Technologies in soil and Water Conservation Engineering,A315021615)&#160; &#160; &#160; &#160;&#160;

Download Full-text

Impacts of soil properties on flow velocity under rainfall events: Evidence from soils across the Loess Plateau

CATENA ◽

10.1016/j.catena.2020.104704 ◽

2020 ◽

Vol 194 ◽

pp. 104704

Author(s):

Liying Sun ◽

John L. Zhou ◽

Qiangguo Cai

Keyword(s):

Soil Properties ◽

Flow Velocity ◽

Loess Plateau ◽

The Loess Plateau ◽

Rainfall Events

Download Full-text

Automated reconstruction of rainfall events responsible for shallow landslides

Natural Hazards and Earth System Science ◽

10.5194/nhess-14-2399-2014 ◽

2014 ◽

Vol 14 (9) ◽

pp. 2399-2408 ◽

Cited By ~ 29

Author(s):

G. Vessia ◽

M. Parise ◽

M. T. Brunetti ◽

S. Peruccacci ◽

M. Rossi ◽

...

Keyword(s):

Rainfall Intensity ◽

Shallow Landslides ◽

Threshold Values ◽

Rainfall Thresholds ◽

Rainfall Events ◽

Mean Intensity ◽

Landslide Occurrence ◽

R Language ◽

Rain Gauges ◽

Rainfall Duration

Abstract. Over the last 40 years, many contributions have identified empirical rainfall thresholds (e.g. rainfall intensity (I) vs. rainfall duration (D), cumulated rainfall vs. rainfall duration (ED), cumulated rainfall vs. rainfall intensity (EI)) for the possible initiation of shallow landslides, based on local and global inventories. Although different methods to trace the threshold curves have been proposed and discussed in literature, a systematic study to develop an automated procedure to select the rainfall event responsible for the landslide occurrence has only rarely been addressed. Objective criteria for estimating the rainfall responsible for the landslide occurrence play a prominent role on the threshold values. In this paper, two criteria for the identification of the effective rainfall events are presented. The first criterion is based on the analysis of the time series of rainfall mean intensity values over 1 month preceding the landslide occurrence. The second criterion is based on the analysis of the trend in the time function of the cumulated mean intensity series calculated from the rainfall records measured through rain gauges. The two criteria have been implemented in an automated procedure that is written in the R language. A sample of 100 shallow landslides collected in Italy from 2002 to 2012 was used to calibrate the procedure. The cumulated event rainfall (E) and duration (D) of rainfall events that triggered the documented landslides are calculated through the new procedure and are fitted with power law in the D, E diagram. The results are discussed by comparing the D, E pairs calculated by the automated procedure and the ones by the expert method.

Download Full-text