The erosive force of rainfall is expressed as rainfall erosivity. Date received month day year colorado discharge permit. United states environmental protection agency npdes. Rainfall erosivity factor for india using modified fourier index. However, the spatiotemporal variations of soil erosion with different return periods, especially at national level, have not been adequately considered. One of these contributing factors is the rainfall erosivity factor r.
Rainfall erosivity results in detachments of soil particles and their transport by. You do not qualify for a waiver from npdes permitting requirements. Investigating rainfall erosivity indices in arid and. Jan 21, 2017 analysis of eventbased soil erosion magnitude with special return periods is essential to appropriately design strategies and adopt soil conservation practices. This precipitation variability led to an important variation over time of the value of the rainfall and runoff erosivity factor. Rainfall erosivity rfactor in europe is a key parameter for estimating soil erosion. The rfactor is a multiannual average index that measures rainfalls kinetic energy. Detailed instructions for calculating a project r factor are provided later in this fact sheet. Pdf determination of rainfall erosivity index r for imo. Evaluation of annual rainfall erosivity index based on daily. Rainfall erosivity event daily rainfall erosivity monthly rainfall erosivity annual rainfall erosivity rainfall data rainfall data rainfall data applicability of regression models rmse, mape, and bias spatial distribution comparison of regression models kriging assessment of three regression equations rj p j 12. Rainfall erosivity estimation based on rainfall data. Rainfall erosivity is an index that describes the power of rainfall to cause soil erosion. Later arnoldus, in 1980 modified the original index so the formula transformed to.
Rainfall erosivity factor r to calculate the rainfall erosivity factor r for the proposed construction project, the applicant for a waiver must obtain a copy of fact sheet 3. If the land is devoid of grasses or vegetation, it will assumed be to be1 where there is a forest. Investigating rainfall erosivity indices in arid and semiarid climates of iran 366 th e subject of rainfall erosivity has been studied worldwide, and various properties of raindrops, such as intensity, velocity, size, and kinetic energy, are among the most frequently used parameters to develop erosivity indices. He also showed, that the fm index is a good approximation of r rainfall erosivity to which it is linearly correlated. The rainfall parameter that expresses the capacity to promote soil erosion is called rainfall erosivity r, and is commonly represented by the indexes ei 30 and ke25. Estimation of erosivity from rainfall data 2 methods. Estimation of erosivity from rainfall data 2 methods soil. If your small construction project is located in an area where epa is the permitting authority and your r factor is less than five, you qualify for a low erosivity waiver lew from. This describes intensity and duration of rainfall in a given geographical area.
Thus, erosivity of precipitation events is a function of their intensity and duration, and of the mass, diameter, and velocity of the raindrops. Rainfall erosivity in europe esdac european commission. Rainfall erosivity and extreme precipitation in the pannonian basin. The new general construction permit 20090009 includes the option allowing small construction site 1 and rainfall erosivity value rvalue for their sites given location and time frame compute to less than or equal to 5.
This is the result of an extensive data collection of high temporal resolution rainfall data from the maximum possible number of countries. Assessing changes in wind erosion climatic erosivity in china. Relationship between soil erodibility, rainfall erosivity and. Improving rainfall erosivity estimates using merged trmm and. From empirical equations rainfall intensities and erosivity index were obtained at 30, 45 and 60 minutes duration of rainfall respectively, and based on 30minute maximum erosive rainfall rainfall. All items must be completed accurately and in their entirety for the application. Investigating rainfall erosivity indices in arid and semiarid. Amount of erosion thus depends upon the combination of the power of rain to cause erosion and the. A the estimated average annual soil loss metric tons hectare 1 r the rainfall and runoff erosivity index. Among the factors of rusle, the calculation of rainfall erosivity factor as per rusle.
Assessing rainfall erosivity indices through synthetic precipitation series and artificial neural networks. Predicting rusle revised universal soil loss equation. Fm takes into account the seasonal variation in the precipitation, analyzing data on fm, for different european regions bergsma, 1980. Numerous indices of rainfall aggressivity erosivity have been. Rainfall erosivity, measured with the rfactor in rusle, accounts for the erosive power of rainfall and the subsequent runoff 4. To obtain annual rainfall erosivity values for this period, historical rainfall erosivity was based on measured data 19982004. Global rainfall erosivity assessment based on hightemporal. Assessing rainfall erosivity indices through synthetic. On the other hand, hourly rainfall data are widely and readily available in china. This paper describes the use of synthetic rainfall series to compute ei. This example is for region 7 colorado river basin region. This variable explained from 72 to 97% of the variation in individual. Table 1 is based on 120 rainfall distribution zones for the continental u. Global rainfall erosivity esdac european commission.
R rainfall runoff erosivity factor the rainfall index plus erosion index plus a factor for any significant runoff from snowmelt. Globally, the mean rainfall erosivity is estimated to be 2,190 mj mm ha1 h1 yr1 and broadly reflects climatic patterns, with the highest values, which are 3 three times highergreater than the mean are found in south america especially around the amazon basin and the caribbean countries, central and parts of east western africa and south east asia. Return period determination the theoretical return period is the inverse of the probability that the event will be exceeded in any given year. Soil erosion assessment using remotely sensed data and ancillary data in the desert of tabernas, southeast spain by yared jillo gobena thesis submitted to the international institute for geoinformation science and earth observation in. Provide the annual erosivity factor number from figure 3 for montana this will be an interpolated whole number ranging from 10 to 40 annual erosivity factor 6. Therefore, in the universal soil loss equation usle 8, the rainfall erosivity factor r was introduced as the product of the rainfall kinetic energy of a storm, classified as erosive by certain criteria, and its maximum 30 min intensity. Spatiotemporal mapping of rainfall erosivity index for. The rainfall erosivity is determined as the product of ke and maximum 30minutes rainfall intensity.
Relationship between soil erodibility, rainfall erosivity. Pdf determination of rainfall erosivity index r for. Spatiotemporal average rainfall erosivity factor map has been generated for india. United states environmental protection agency stormwater. The rainfall stations that were considered were those that had longterm rainfall data with 30 or 60 minutes interval. Rusle2 uses six factors for climatic erosivity, soil erodibility, slope length, slope steepness, covermanagement, and support practices to compute soil loss. High temporal resolution rainfall measurements, for example 15 min or 30 min, are important for the calculation of erosivity. The rainfall erosivity and the other climatic data is.
The rfactor is a multiannual average index that measures rainfalls kinetic energy and. Erosivity is used around the world for assessing and predicting rates of soil erosion on agricultural lands. If your small construction project is located in an area where epa is the permitting authority and your r factor is less than five, you qualify for a low erosivity. Estimating the rainfall erosivity factor from monthly precipitation data. When the index approaches zero, the annual erosivity is uniformly distributed in each month, and when it equals 1, the erosivity is concentrated in one month. The rainfall erosivity index for a rainfall event energyintensity values ei30 is calculated from the total kinetic energy and maximum 30min intensity of individual events. In this study, within the erosivity index, the use of 6 min rainfall intervals during erosive rainfall give estimates of around 10% more erosivity than the 30 min time intervals and 33% more rainfall erosivity than the 60 min rainfall measurements. Index values, e, where e is the total storm kinetic energy per unit area, and is.
The sum of the ei30 values corresponds to rainfall erosivity, also called the rfactor of. Finally, the anual average rainfall erosivity was obtained for the period evaluated performing the sum of annual rainfall erosivity divided by number of years. The lowest values are mainly found in mid and high. Estimation of rainfall erosivity using 5 to 60minute. Rusle2 is a powerful tool for conservation planning, inventorying erosion rates over large. Preliminary results of rainfall erosivity mapping for poland. Finally rainfall purchase order template pdf erosivity map for isfahan province created by using cokriging method.
The results obtained allow observation of differences in space and time of the distribution of this index. Attempts were therefore made to estimate the erosivity index by using a few rainfall data such as storm amount and duration istok et al. Pdf determination of rainfall erosivity index r for imo state. Usda developed the erosivity index table ei table, provided here in table 1, to show how the annual erosivity factor is distributed throughout the year in twoweek increments. The literature illustrates the successful use of this index which provides a summary assessment of the probability of rainfall with significant erosive effects. Improving rainfall erosivity estimates using merged trmm. Pdf rainfall erosivity is the capability of rainfall to cause soil loss from hillslopes by water. This is actually the kinetic energy of rainfall events k soil erodibility factor l slope length factor s slope steepness factor c plant cover. Estimating rainfall erosivity from daily precipitation using. The erosivity is computed for individual daily storms and then added altogether to get the weekly, monthly or annual erosivity values. Estimation of rainfall erosivity using 5 to 60minute fixed.
The calculations of these indexes requires pluviographical records, that are difficult to obtain in brazil. Oct 01, 2017 rainfall erosivity is an index that describes the power of rainfall to cause soil erosion. Using correlation analysis, longterm 30minute and 60minute rainfall data were used to develop storm erosion indices ei30. The greater is the proportion of above content in the soil, more will be the soil resistant to erosion. Erosivity is a measure of the potential ability of soil, regolith, or other weathered material to be eroded by rain, wind, or surface runoff. Rainfall erosivity index pdf rainfall erosivity is defined as the aggressiveness of the rain to punyavachanam mantras pdf cause erosion. Erosivity index calculator results an erosivity index value of 11.
Sum of ei30 of each month, was the annual rainfall erosivity. Pdf on jan 1, 2017, o o okorafor and others published determination of rainfall erosivity index r for imo state, nigeria find, read and. The objective of this study was to develop average annual rainfall erosivity rvalues for selected rainfall stations in the fsm by using local rainfall data for each station. The r factor was developed from the relationship between rainfall and elevation of the gauge stations adjud 103 m, bacau 184 m and tg. However, these data are often unavailable in many areas of the world. The global rainfall erosivity database, named hereafter as gloreda, contains erosivity values estimated as rfactors refer to the method section from 3,625 stations distributed in 63 countries worldwide. Rainfall erosivity calculations the erosivity of a single erosive rainfall event. Erosivity estimations from different resolution data in a. Jan 21, 2016 ei 30 is the most commonly used rainfall erosivity index, where e is the total kinetic energy per unit area during a precipitation event mjha 1 and i 30 is its peak 30min intensity mmha. An erosivity map was also produced by shamshad et al.
He also showed, that the fm index is a good approximation of r rainfall erosivity. Soil erosion assessment using remotely sensed data and. Therefore, the present study aimed to zone rainfall erosivity index r factor as. Ei 30 is calculated from the total kinetic energy and the maximum 30min rainfall intensity of a storm. Rainfall erosivity is the power of rainfall to cause soil erosion by water. The 30min rainfall erosivity index ei 30 is commonly used in the universal soil loss equation for predicting soil loss from agricultural hillslopes.
The coefficient a is given by two values, a and a, where a is used for the warm months of april through. Assessing changes in wind erosion climatic erosivity in. In this study, we developed rainfall erosivity r factors for the islands of pohnpei, chuuk, and yap. Evaluation of annual rainfall erosivity index based on. K soil erodibility factor the soil rate per erosion index unit for a specified soil as measured on a standard plot, which is defined as a 72. Seasonal rainfall erosion index values computed by adding the ei values of storms 0. Finally licznar 2004b suggested the necessity of elevation use to aid the geostatistical mapping of rainfall erosivity. Rainfall erosivity for erosive events was calculated using different set interval data. The most common rainfall erosivity index is the r factor of usle. Ei 30 is the most commonly used rainfall erosivity in. The rainfall erosivity classes determined by means of the fournier index oliver, 1980, qtd.
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