Naturally rainfall-induced changes in runoff-associated nitrogen and phosphorus losses in purple soil area: roles of land disturbance and plot length

2021 ◽  
Author(s):  
Ke Liang ◽  
Binghui He
Keyword(s):  
Rainfall Intensity ◽  
Purple Soil ◽  
Rainfall Events ◽  
Dissolved Phosphorus ◽  
Land Disturbance ◽  
P Concentration ◽  
Long Duration ◽  
Artificial Disturbance ◽  
Runoff Rate ◽  
Sloping Land

<p>Severe soil erosion occurs in southwestern China owing to the large expanses of human disturbance and sloping land. This field monitoring study was conducted during the rainy season to record the rainfall events, runoff, sediment yield, nitrogen, and phosphorous loss in 20-, 40-, and 60-m plots under conditions of artificial disturbance or natural restoration on a 15° slope in the purple soil area of southwestern China. The concentrations and loss amounts of total nitrogen (TN), total dissolved nitrogen (TDN), ammonium-nitrogen (NH4-N) and nitrate-nitrogen (NO<sub>3</sub>-N), total phosphorus (TP), total dissolved phosphorus (TDP) and orthophosphate (PO<sub>4</sub>-P) were comparatively determined. The highest N concentration was observed in long duration and soft rainfall events across all plots. The highest P concentration in artificial disturbed plots was found in long duration and intensive rainfall events while it was recordeds for measured variables were dominantly recorded under the long duration and lowest soft rainfall events in naturally restored plots intensity., while The the highest loss amounts for N and P in different forms for these variablesalmostmostly appeared under high rainfall intensity. Land disturbances differed orthophosphate PO<sub>4</sub>-P concentration in 20--m plot and and loss amounts of of measured variables N and P with different forms across in all plots. Plot lengths differed total dissolved phosphorus TDP concentration in natural restored plot and loss amounts of total dissolved nitrogenTDN and orthophosphate PO<sub>4</sub>-P in artificially disturbed plots. Naturally restoration reduced loss amounts of total nitrogen and total phosphorus by 69.4%62.14-79.05% and 79.28-83.43% TN, 68.8% TDN, 71.2% NH<sub>4</sub>-N, 74.3% NO<sub>3</sub>-N, 81.5% TP, 71.9% TDP and 70.0% PO<sub>4</sub>-P loss amounts comparedrelative to artificial disturbance, respectively. There were significant interrelationships among N and P concentrations in different forms in two land disturbance plots, while nitrate-NO<sub>3</sub>-nitrogenN concentration hadwas significantly negatively negative correlatedion with rainfall intensity and runoff rate in artificialally disturbanceed plots. Rainfall intensity was logarithmically correlated with TN, NO<sub>3</sub>-N concentrations in artificially disturbed plots and with NO<sub>3</sub>-N concentration in naturally restored plots. Runoff rate was logarithmically correlated with TN, TDN and NO<sub>3</sub>-N concentrations in artificially disturbed plots. Our results highlight the effects of land disturbance and plot length on nutrient losses in sloping land.</p>

scholarly journals Runoff-associated nitrogen and phosphorus losses under natural rainfall events in purple soil area: the role of land disturbance and slope length

2021 ◽  
Author(s):  
Ke Liang ◽  
Xiaorong He ◽  
Binghui He ◽  
Xiaomeng Guo ◽  
Tianyang Li
Keyword(s):  
Total Phosphorus ◽  
Purple Soil ◽  
Slope Length ◽  
Rainfall Events ◽  
Dissolved Phosphorus ◽  
Natural Rainfall ◽  
Land Disturbance ◽  
Natural Restoration ◽  
Artificial Disturbance

Abstract Land disturbance and slope length play key roles in affecting runoff-associated nitrogen (N) and phosphorus (P) losses in different forms under natural rainfall. Field monitoring was conducted in nine plots located parallel on a 15° purple slope in southwest China. Three slope lengths (20-, 40-, 60-m) combined with measures of artificial disturbance and natural restoration were implemented. The highest N concentration was observed in soft rainfall events across all plots. The highest P concentration was recorded in heavy rainfall events for the artificially disturbed plots and in soft rainfall events for the naturally restored plots. Land disturbance differed orthophosphate concentration in 20-m plot, and affected N and P loss amounts in different forms. Slope length differed total dissolved phosphorus concentration in naturally restored plots, and also differed the loss amounts of total dissolved nitrogen and orthophosphate in artificially disturbed plots. Naturally restoration reduced loss amounts of total nitrogen and total phosphorus by 62.14–79.05% and 79.28–83.43% relative to artificial disturbance, respectively. Concentrations of nitrate-nitrogen, total phosphorus and dissolved phosphorus were closely correlated with rainfall and runoff variables, respectively, in artificially disturbed plots. Our results highlight the dominant role of natural restoration in reducing erosion and nutrient loss in sloping land.

scholarly journals The Definition and Characteristics of Regional Rainfall Events Demonstrated by Warm Season Precipitation over the Beijing Plain

2015 ◽  
Vol 16 (1) ◽  
pp. 396-406 ◽  
Author(s):  
Rucong Yu ◽  
Haoming Chen ◽  
Wei Sun
Keyword(s):  
Rainfall Intensity ◽  
Numerical Models ◽  
Warm Season ◽  
Rainfall Events ◽  
Beijing Plain ◽  
Long Duration ◽  
The Given ◽  
Insight Into ◽  
Regional Rainfall ◽  
Key Parameter

Abstract In this study, a regional rainfall event (RRE) is defined by observed rainfall at multiple, well-distributed stations in a given area. Meanwhile, a regional rainfall coefficient (RRC), which could be used to classify local rain (LR) and regional rain (RR) in the given area, is defined to quantify the spatiotemporal variation of rainfall events. As a key parameter describing the spread of rainfall, RRC, together with duration and intensity, presents an effort to explore more complete spatiotemporal organization and evolution of RREs. Preliminary analyses of RREs over the Beijing plain reveal new, interesting characteristics of rainfall. The RRC of RRE increases with longer duration and stronger intensity. Most of the RREs with maximum peak rainfall intensity below 2 mm h−1 or duration shorter than 3 h have RRC less than 0.4, indicating that these events are not uniformly spread over the region. Thus, they are reasonably classified into LR. RREs with RRC above 0.5 could be classified into RR, which usually lasts longer than 4 h and has primary peak rainfall occurring from 1700 to 0600 LST. For most of the intense long-duration RR, evolutions of RRC and rainfall intensity are not consistent. The RRC reaches a maximum a few hours after the peak intensity was reached. The results of this study enrich the understanding of rainfall processes and provide new insight into understanding and quantifying the space–time characteristics of rainfall. These findings have great potential to further evaluate cloud and precipitation physics as well as their parameterizations in numerical models.

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

2021 ◽  
Author(s):  
Marcelle Martins Vargas ◽  
Samuel Beskow ◽  
Carlos Rogério de Mello ◽  
Maíra Martim de Moura ◽  
Maria Cândida Moitinho Nunes ◽  
...  
Keyword(s):  
Rainfall Events ◽  
Long Duration

scholarly journals Assessment of Rainfall-Induced Landslide Distribution Based on Land Disturbance in Southern Taiwan

2021 ◽  
Vol 10 (4) ◽  
pp. 209
Author(s):  
Chih-Ming Tseng ◽  
Yie-Ruey Chen ◽  
Chwen-Ming Chang ◽  
Yung-Sheng Chue ◽  
Shun-Chieh Hsieh
Keyword(s):  
Satellite Image ◽  
Extreme Rainfall ◽  
Land Area ◽  
Rainfall Events ◽  
Land Disturbance ◽  
Bare Land ◽  
Southern Taiwan ◽  
The Impact ◽  
Landslide Distribution ◽  
The Relationship

This study explores the impact of rainfall on the followed-up landslides after a severe typhoon and the relationship between various rainfall events and the occurrence, scale, and regional characteristics of the landslides, including second landslides. Moreover, the influence of land disturbance was evaluated. The genetic adaptive neural network was used in combination with the texture analysis of the geographic information system for satellite image classification and interpretation to analyze land-use change and retrieve disaster records and surface information after five rainfall events from Typhoon Morakot (2009) to Typhoon Nanmadol (2011). The results revealed that except for extreme Morakot rains, the greater the degree of slope disturbance after rain, the larger the exposed slope. Extreme rainfall similar to Morakot strikes may have a greater impact on the bare land area than on slope disturbance. Moreover, the relationship between the bare land area and the index of land disturbance condition (ILDC) is positive, and the ratio of the bare land area to the quantity of bare land after each rainfall increases with the ILDC. With higher effective accumulative rainfall on the slope in the study area or greater slope disturbance, the landslide area at the second landslide point tended to increase.

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

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.

scholarly journals Seasonal Variation of the Diurnal Cycle of Rainfall in Southern Contiguous China

2008 ◽  
Vol 21 (22) ◽  
pp. 6036-6043 ◽  
Author(s):  
Jian Li ◽  
Rucong Yu ◽  
Tianjun Zhou
Keyword(s):  
Seasonal Variation ◽  
Diurnal Cycle ◽  
Radiative Forcing ◽  
Early Morning ◽  
Rain Gauge ◽  
Rainfall Events ◽  
Late Afternoon ◽  
Long Duration ◽  
China Region ◽  
Afternoon Peak

Abstract Hourly station rain gauge data are employed to study the seasonal variation of the diurnal cycle of rainfall in southern contiguous China. The results show a robust seasonal variation of the rainfall diurnal cycle, which is dependent both on region and duration. Difference in the diurnal cycle of rainfall is found in the following two neighboring regions: southwestern China (region A) and southeastern contiguous China (region B). The diurnal cycle of annual mean precipitation in region A tends to reach the maximum in either midnight or early morning, while precipitation in region B has a late-afternoon peak. In contrast with the weak seasonal variation of the diurnal phases of precipitation in region A, the rainfall peak in region B shifts sharply from late afternoon in warm seasons to early morning in cold seasons. Rainfall events in south China are classified into short- (1–3 h) and long-duration (more than 6 h) events. Short-duration precipitation in both regions reaches the maximum in late afternoon in warm seasons and peaks in either midnight or early morning in cold seasons, but the late-afternoon peak in region B exists during February–October, while that in region A only exists during May–September. More distinct differences between regions A and B are found in the long-duration rainfall events. The long-duration events in region A show dominant midnight or early morning peaks in all seasons. But in region B, the late-afternoon peak exists during July–September. Possible reasons for the difference in the diurnal cycle of rainfall between the two regions are discussed. The different cloud radiative forcing over regions A and B might contribute to this difference.

scholarly journals Derivation and evaluation of landslide-triggering thresholds by a Monte Carlo approach

2014 ◽  
Vol 18 (12) ◽  
pp. 4913-4931 ◽  
Author(s):  
D. J. Peres ◽  
A. Cancelliere
Keyword(s):  
Monte Carlo ◽  
Slope Stability ◽  
Power Law ◽  
Rainfall Intensity ◽  
Antecedent Rainfall ◽  
Rainfall Events ◽  
Physically Based ◽  
Power Law Equation ◽  
Triggering Rainfall ◽  
Landslide Triggering

Abstract. Assessment of landslide-triggering rainfall thresholds is useful for early warning in prone areas. In this paper, it is shown how stochastic rainfall models and hydrological and slope stability physically based models can be advantageously combined in a Monte Carlo simulation framework to generate virtually unlimited-length synthetic rainfall and related slope stability factor of safety data, exploiting the information contained in observed rainfall records and field-measurements of soil hydraulic and geotechnical parameters. The synthetic data set, dichotomized in triggering and non-triggering rainfall events, is analyzed by receiver operating characteristics (ROC) analysis to derive stochastic-input physically based thresholds that optimize the trade-off between correct and wrong predictions. Moreover, the specific modeling framework implemented in this work, based on hourly analysis, enables one to analyze the uncertainty related to variability of rainfall intensity within events and to past rainfall (antecedent rainfall). A specific focus is dedicated to the widely used power-law rainfall intensity–duration (I–D) thresholds. Results indicate that variability of intensity during rainfall events influences significantly rainfall intensity and duration associated with landslide triggering. Remarkably, when a time-variable rainfall-rate event is considered, the simulated triggering points may be separated with a very good approximation from the non-triggering ones by a I–D power-law equation, while a representation of rainfall as constant–intensity hyetographs globally leads to non-conservative results. This indicates that the I–D power-law equation is adequate to represent the triggering part due to transient infiltration produced by rainfall events of variable intensity and thus gives a physically based justification for this widely used threshold form, which provides results that are valid when landslide occurrence is mostly due to that part. These conditions are more likely to occur in hillslopes of low specific upslope contributing area, relatively high hydraulic conductivity and high critical wetness ratio. Otherwise, rainfall time history occurring before single rainfall events influences landslide triggering, determining whether a threshold based only on rainfall intensity and duration may be sufficient or it needs to be improved by the introduction of antecedent rainfall variables. Further analyses show that predictability of landslides decreases with soil depth, critical wetness ratio and the increase of vertical basal drainage (leakage) that occurs in the presence of a fractured bedrock.

Herbicide loss in runoff: effects of herbicide properties, slope, and rainfall intensity

Soil Research ◽  
2004 ◽  
Vol 42 (1) ◽  
pp. 17 ◽  
Author(s):  
K. Müller ◽  
M. Trolove ◽  
T. K. James ◽  
A. Rahman
Keyword(s):  
Rainfall Intensity ◽  
Water Solubility ◽  
Small Scale ◽  
Herbicide Application ◽  
Rainfall Events ◽  
Kd Values ◽  
Loam Soil ◽  
The Impact ◽  
Field Plots ◽  
Dissolved Form

Runoff potential of 5 herbicides (acetochlor, atrazine, hexazinone, pendimethalin, and terbuthylazine) was evaluated in a small-scale study under simulated rainfall on a cultivated Hamilton clay loam soil. At 24 h after herbicide application, rainfall events of different intensities were simulated to 0.5-m2 field plots with 20% (70, 88, and 111 mm/h) and 30% (60, 70, and 80 mm/h) slope, respectively. The objective of this study was to compare the behaviour of pesticides covering a range of properties under identical hydrodynamic conditions. Sediment amounts and herbicide concentrations were determined in the runoff samples. As the transported sediment amounts were not sufficient for chemical analyses, herbicide residues attached to sediment were estimated using Kd values determined locally for the soil. Whereas pendimethalin concentrations followed no noticeable pattern, the concentrations for the other herbicides were highest in the first runoff samples, and decreased exponentially with further rain. Results show that herbicides were primarily transported in their dissolved form with the exception of pendimethalin. Slope affected cumulative runoff, sediment, and herbicide losses significantly (P < 0.05). The impact of increased rainfall intensity on runoff initiation followed a similar trend, but herbicide losses from plots exposed to different intensities were not always significant. Losses dissolved in runoff from plots with 20% slope were ≤1% of the applied herbicide, whereas on plots with 30% slope the maximum recorded loss was 65%. Here, losses for all herbicides ranged between 1 and 7% at 60 mm/h and 8 and 65% at 80 mm/h. Exports of herbicides with moderate solubility were negatively correlated with their Kd values and their water solubility.

How to account for misclassification costs in shallow-landslide rainfall thresholds?

2021 ◽  
Author(s):  
Paolo Frattini ◽  
Gianluca Sala ◽  
Camilla Lanfranconi ◽  
Giulia Rusconi ◽  
Giovanni Crosta
Keyword(s):  
False Alarm ◽  
Rainfall Intensity ◽  
Rainfall Threshold ◽  
Shallow Landslides ◽  
False Alarms ◽  
Rainfall Thresholds ◽  
Rainfall Events ◽  
Misclassification Costs ◽  
Triggering Events ◽  
The Cost

&lt;p&gt;Rainfall is one of the most significant triggering factors for shallow landslides. The early warning for such phenomena requires the definition of a threshold based on a critical rainfall condition that may lead to diffuse landsliding. The developing of these thresholds is frequently done through empirical or statistical approaches that aim at identifying thresholds between rainfall events that triggered or non-triggered landslides. Such approaches present several problems related to the identification of the exact amount of rainfall that triggered landslides, the local geo-environmental conditions at the landslide site, and the minimum rainfall amount used to define the non-triggering events. Furthermore, these thresholds lead to misclassifications (false negative or false positive) that always induce costs for the society. The aim of this research is to address these limitations, accounting for classification costs in order to select the optimal thresholds for landslide risk management.&lt;/p&gt;&lt;p&gt;Starting from a database of shallow landslides occurred during five regional-scale rainfall events in the Italian Central Alps, we extracted the triggering rainfall intensities by adjusting rain gouge data with weather radar data. This adjustment significantly improved the information regarding the rainfall intensity at the landslide site and, although an uncertainty related to the exact timing of occurrence has still remained. Therefore, we identified the rainfall thresholds through the Receiver Operating Characteristic (ROC) approach, by identifying the optimal rainfall intensity that separates triggering and non-triggering events. To evaluate the effect related to the application of different minimum rainfall for non-triggering events, we have adopted three different values obtaining similar results, thus demonstrating that the ROC approach is not sensitive to the choice of the minimum rainfall threshold. In order to include the effect of misclassification costs we have developed cost-sensitive rainfall threshold curves by using cost-curve approach (Drummond and Holte 2000). As far as we know, this is the first attempt to build a cost-sensitive rainfall threshold for landslides that allows to explicitly account for misclassification costs. For the development of the cost-sensitive threshold curve, we had to define a reference cost scenario in which we have quantified several cost items for both missed alarms and false alarms. By using this scenario, the cost-sensitive rainfall threshold results to be lower than the ROC threshold to minimize the missed alarms, the costs of which are seven times greater than the false alarm costs. Since the misclassification costs could vary according to different socio-economic contexts and emergency organization, we developed different extreme scenarios to evaluate the sensitivity of misclassification costs on the rainfall thresholds. In the scenario with maximum false-alarm cost and minimum missed-alarm cost, the rainfall threshold increases in order to minimize the false alarms. Conversely, the rainfall thresholds decreases in the scenario with minimum false-alarm cost and maximum missed-alarm costs. We found that the range of variation between the curves of these extreme scenarios is as much as half an order of magnitude.&lt;/p&gt;

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

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2268
Author(s):  
Wenbin Ding ◽  
Fei Wang ◽  
Kai Jin ◽  
Jianqiao Han ◽  
Qiang Yu ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Heavy Rainfall ◽  
Rainfall Intensity ◽  
Rainfall Amount ◽  
The Loess Plateau ◽  
Total Rainfall ◽  
Rainfall Events ◽  
Rainfall Duration ◽  
Rainfall Frequency ◽  
Annual Total

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.

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