Abstract
Rainfall erosivity (R factor) has been determined for Sierra Leone using monthly precipitation data covering 1960–2013 using Fournier (FI) and modified Fournier (MFI) indices. Mann–Kendall, Pearson’s correlation and Sen’s slope tests were used to establish the trend in time series rainfall data and their correlation. The study showed that there is a decreasing trend in annual rainfall in all the districts and the average annual rainfall varies between 1400.7 and 3027 mm, with high variability in the southeast and western regions compared to northern region. Rainfall erosivity was in the low to extremely severe category ranging from 21.7 to 166.8 for Fournier index and 95.4 to 264.6 for modified Fournier index. The year 1998 recorded the highest erosivity with values ranging from severe to extremely severe. The rainfall aggressiveness varied from low to extremely severe. Trend analysis was significant for values of − 1.82 ≥ Z ≤ − 1.57 at the 99% and 95% confidence levels, respectively, with two-tailed tests. No significant change in the precipitation trend was observed for some districts at the 95% confidence level. However, a significant change was noted for Bo, Pujehun and Tonkolili districts at the 99% confidence level. Sen’s slope (Q) test revealed a non-significant decreasing slope magnitude for all 14 districts. Pearson’s correlation coefficients showed significant correlation between annual rainfall and erosivity but with stronger correlation for modified Fournier index than Fournier index. The decreasing rainfall trend and high erosivity may have challenging implications for natural resource management including vegetation, soil and water resources under current climate conditions.








Similar content being viewed by others
References
Aguilar E, Peterson TC, Obando PR, Frutos R, Retana JA, Solera M, Soley J, García IG, Araujo RM, Santos AR, Valle VE, Brunet M, Aguilar L, Álvarez L, Bautista M, Castañón C, Herrera L, Ruano E, Sinay JJ, Sánchez E, Oviedo GIH, Obed F, Salgado JE, Vázquez JL, Baca M, Gutiérrez M, Centella C, Espinosa J, Martínez D, Olmedo B, Espinoza CEO, Núñez R, Haylock M, Benavides H, Mayorga R (2005) Changes in precipitation and temperature extremes in Central America and northern South America, 1961–2003. J Geophys Res 110:D23107. https://doi.org/10.1029/2005JD006119
Aguilar E, Auer I, Brunet M, Peterson TC, Wieringa J (2003) Guidelines on climate metadata and homogenization, WMO-TD No. 1186, 55 pp., World Meteorol. Org., Geneva, Switzerland
Amara DMK, Oladele TA (2014) Estimation of soil erodibility and erosivity of rainfall patterns in Njala land resource area of southern Sierra Leone. Res J Agric Sci 5(2):163–167
Angima SD, Scott DE, O’Neil MK, Weesies GA (2003) Soil erosion prediction using RUSLE for Central Kenya highland conditions. Agric Ecosyst Env 97(1/3):295–308
Angulo-Martínez M, Beguería S (2009) Estimating rainfall erosivity from daily precipitation records: a comparison among methods using data from the Ebro Basin (NE Spain). J Hydrol 379:111–121. https://doi.org/10.1016/j.jhydrol.2009.09.051
Arnoldus HMJ (1980) An approximation of the rainfall factor in the universal soil loss equation. In: De Boodt M, Gabriels D (eds) Assessment of erosion. John Wiley & Sons, Chichister, pp 127–132
Bazzano MGP, Eltz FLF, Cassol EA (2010) Erosivity and hydrological characteristics of rainfalls in Rio Grande (RS, Brazil). Revista Brasileira de Ciência do Solo 34:235–244
Bertol I, Leite D, Engel FL, Cogo NP, González AP (2007) Erodibility of a Typic Hapludox evaluated under field conditions. Revista Brasileira de Ciência do Solo 31:541–549. https://doi.org/10.1590/S0100-06832007000300014
Bertol I, Zoldan Junior WA, Fabian EL, Zavaschi E, Pegoraro R, Gonzáles AP (2008) Effect of chiselling and rainfall erosivity on some characteristics of water erosion in a Nitosol under distinct management systems. Revista Brasileira de Ciência do Solo 32:747–757. https://doi.org/10.1590/S0100-06832008000200027
Bhalme HN (1991) El Nino-Southern Oscillation (ENSO) - Onset, growth and decay. The WMO/IMD Training Course in Monsoon Meteorology, Education and Training Programme, WMO/TD -No 496, 84–87.
Bomah AK (1988) An analysis of the physical and land use variables affecting soil erosion of Sierra Leone, Doctoral Dissertation, Clark University, U.S.A.
Capolongo D, Diodato N, Mannaerts CM, Piccarreta M, Strobl RO (2008) Analyzing temporal changes in climate erosivity using a simplified rainfall erosivity model in Basilicata (southern Italy). J Hydrol 356:119–130
Calvo JC (1998) Suspended sediment yield prediction models for Costa Rican watersheds. Hydrol Humid Tropic Environ 253:27–33
Calvo-Alvarado JC, Gregory JD (1997). Predicting mean annual runoff and suspended sediment yield in rural watersheds in North Carolina. Water Resources Research Institute of the University of North Carolina Report 307
De Longueville HYC, Kindo I, François GF, Ozerc P (2016) Long-term analysis of rainfall and temperature data in Burkina Faso (1950–2013). Int J Climatol. https://doi.org/10.1002/joc.4640
Essel P, Glover ET, Yeboah S, Adjei-Kyereme Y, Yawo IND, Nyarku M, Asumadu-Sakyi GS, Gbeddy GK, Agyiri YA, Ameho EM, Aberikae EA (2016) Rainfall erosivity index for the Ghana Atomic Energy Commission site. SpringerPlus 5:465. https://doi.org/10.1186/s40064-016-2100-1
GoSL (2007) National adaptation programme of action (NAPA). Final Report. Government of Sierra Leone. Ministry of Transport and aviation, Republic of Sierra Leone, West Africa
GoSL (2009) Second national communication on climate change. Government of Sierra Leone. Republic of Sierra Leone, West Africa
Fournier F (1960) Climat et érosion. La relation entre l'érosion du sol par l'eau et les précipitations atmosphériques. [Relationship between soil erosion by water and rainfall]. Presses Universitaires de France, Paris. (In French)
Frazer-Williams RAD, Benjamin RGP, Kanu BD, Lahai SMG, Kanneh SM Jr., Dreiser C (2014) Environmental assessment and evaluation of natural disaster risk and mitigation in Freetown. Urban planning project 2011–2014, EuropeAid/128037/D/SER/SL-Cris. No.:FED/2010/250–190
Hoyos N, Waylen PR, Jaramillo A (2005) Seasonal and spatial patterns of erosivity in a tropical watershed of the Colombian Andes. J Hydrol 314:177–191. https://doi.org/10.1016/j.jhydrol.2005.03.014
Kendall M (1975) Rank correlation measures. Charles Griffin, London, p 202
Kinnell PIA (2010) Event soil loss, runoff and the universal soil loss equation family of models: a review. J Hydrol 385:384–397. https://doi.org/10.1016/j.jhydrol.2010.01.024
Konin TA (2015) Climate change adaptation strategies: water resources management in Senegal and Sierra Leone. Dissertation, Johns Hopkins University, Maryland, USA
Lapworth DJ, MacDonald AM, Krishan G, Rao MS, Gooddy DC, Darling WG (2015) Groundwater recharge and age-depth profiles of intensively exploited groundwater resources in Northwest India. Geophys Res Lett 42:7554–7562. https://doi.org/10.1002/2015GL065798.
Lee JH, Heo JH (2011) Evaluation of estimation methods for rainfall erosivity based on annual precipitation in Korea. J Hydrol 409(1–2):30–48
Lombardi Neto F, Moldenhauer WC (1992) Rainfall erosivity — its distribution and relationship with soil loss at Campinas, state of São Paulo, Brazil. Bragantia 51:189–196. https://doi.org/10.1590/S0006-87051992000200008
Mann HB (1945) Non-parametric tests against trend. Econometrica 33:245–259
McSweeney C, New M, Lizcano G (2010) UNDP climate change country profiles: Sierra Leone. UNDP. Retrieved on July 27, 2019 at http://country-profiles.geog.ox.ac.uk
Mello CR, Sá MAC, Curi N, Mello JM, Viola MR, Silva AM (2007) Monthly and annual rainfall erosivity for Minas Gerais state. Pesq Agrop Brasileira 42:537–545. https://doi.org/10.1590/S0100-204X2007000400011
Meusburger K, Steel A, Panagos P, Montanarella L, Alewell C (2011) Spatial and temporal variability of rainfall erosivity factor for Switzerland. Hydrol Earth Syst Sci Discus 8:8291–8314. https://doi.org/10.5194/hessd-8-8291-2011
Mezősi G, Bata T (2016) Estimation of the changes in the rainfall erosivity in Hungary. J Environ Geog 9(3–4):43–48. https://doi.org/10.1515/jengeo-2016-0011
Nearing MA (2001) Potential changes in rainfall erosivity in the United States with climate change during the 21st century. J Soil Water Conservation 56:229–232
Nearing MA, Jetten V, Baffaut C, Cerdan O, Couturier A, Hernandez M, le Bissonnais Y, Nichols MH, Nunes JP, Renschler CS, Souchère V, van Oost K (2005) Modelling response of soil erosion and runoff to changes in precipitation and cover. Catena 61:131–154. https://doi.org/10.1016/j.catena.2005.03.007
Oduro-Afriyie K (1996) Rainfall erosivity map for Ghana. Geoderma 74:161–166
Oliveira PTS, Alves ST, Rodrigues DBB, Panachuki E (2011a) Erosion risk mapping applied to environmental zoning. Water Resour Manag 25:1021–1036. https://doi.org/10.1007/s11269-010-9739-0
Oliveira PTS, Rodrigues DBB, Alves ST, Carvalho DF, Panachuki E (2011b) Spatial varibility of the rainfall erosive potencial in the State of Mato Grosso do Sul, Brazil, Brazil. Engenharia Agrícola 32:69–79. https://doi.org/10.1590/S0100-69162012000100008
Onchev NG (1985) Universal index for calculating rainfall erosivity. In: El-Swaify SA, Moldenhauer WC, Lo A (eds) Soil erosion and conservation. Soil Conservation Society of America, Ankeny, pp 424–431
Ozer P, Mahamoud A (2013) Recent extreme precipitation and temperature changes in Djibouti City (1966–2011). J Climatol 2013:1–8. https://doi.org/10.1155/2013/928501
Pruski FF, Nearing MA (2002) Climate-induced changes in erosion during the 21st century for eight U.S. locations. Water Resour Res 38(12):1298. https://doi.org/10.1029/2001WR000493
Renard KG, Foster GR, Weesies GA, McCool DK (1996) Predicting soil erosion by water. A guide to conservation planning with the revised universal soil loss equation (RUSLE). Agric. Handbook 703.
Renard KG, Freimund JR (1994) Using monthly precipitation data to estimate the R-factor in the revised USLE. J Hydrol 157:287–306. https://doi.org/10.1016/0022-1694(94)90110-4
Resilience Policy Team (2015) Sierra Leone climate action report. Resilience policy team, Irish Aid. Republic of Sierra Leone, West Africa
Sen PK (1968) Estimates of the regression coefficient based on Kendall’s tau. J Am Stat Assoc 63:1379–1389. https://doi.org/10.1080/01621459.1968.10480934
Silva AM (2004) Rainfall erosivity map for Brazil. Catena 57:251–259. https://doi.org/10.1016/j.catena.2003.11.006
Silva RB, Iori P, Silva FAM (2009) Proposition and compare of equations to estimate the rainfall erosivity in two cities of São Paulo state. Irrigation 14:533–547
Silva RB, Iori P, Armesto C, Bendini HN (2010) Assessing rainfall erosivity with artificial neural networks for the Ribeira Valley, Brazil. Int J Agron. https://doi.org/10.1155/2010/365249
Strangeways IC (1996) Back to basics: the ‘met. enclosure’: part 2(b) — raingauges, their errors. Weather 51:298–303
Tarawalli P (2012) Diagnostic analysis of climate change and disaster management in relation to the PRSP III in Sierra Leone. Sierra Leone, Freetown
Trewin BC (2010) Exposure, instrumentation and observing practice effects on land temperature measurements. Wiley Interdis Rev: Clim Change 1:490–506
USAID (2016) Climate change risk in Sierra Leone. Country Fact Sheet. pp. 1–5
Vincent E et al (2011) Observed trends in indices of daily and extreme temperature and precipitation for the countries of the western Indian Ocean, 1961–2008. J Geophys Res 116:D10108. https://doi.org/10.1029/2010JD015303
Vincent LA, Wang XL, Milewska EJ, Wan H, Yang F, Swail V (2012) A second generation of homogenized Canadian monthly surface air temperature for climate trend analysis. J Geophys Res 117:D18110. https://doi.org/10.1029/2012JD017859
Wang XL (2008) Accounting for autocorrelation in detecting meanshifts in climate data series using the penalized maximal t or F test. J Appl Meteorol Climatol 47:2423–2444. https://doi.org/10.1175/2008JAMC1741.1
Wang XL, Feng Y (2009) RHtestsV3 user manual, report, 26 pp., Clim. Res. Div., Atmos. Sci. and Technol. Dir., Sci. and Technol. Branch, Environ. Canada, Gatineau, Quebec, Canada. Retrieved on July 20, 2019 at http://cccma.seos.uvic.ca/ETCCDI/software.shtml
Wischmeier WH (1959) A rainfall erosion index for a universal soil- loss equation. Soil Sci Soc Am Proc 23(3):246–249. https://doi.org/10.2136/sssaj1959.03615995002300030027x
Wischmeier WH, Smith DD (1978) Predicting rainfall erosion losses. A guide to conservation planning. Agriculture Handbook No. 537. U.S. Department of Agriculture, Washington DC.
World Bank (2017) Sierra Leone: rapid damage and loss assessment of August 14th, 2017 landslides and floods in the Western Area. http://documents.worldbank.org/curated/en/523671510297364577/Sierra-Leone-Rapid-damage-and-loss-assessment-of-August-14th-2017-landslides-and-floods-in-the-western-area. Accessed 25 November 2017.
Zhai P, Zhang X, Wan H, Pan X (2005) Trends in total precipitation and frequency of daily precipitation extremes over China. J Clim 18:1096–1108
Acknowledgements
The authors are grateful to COMSATS University Islamabad (former CIIT) and The World Academy of Sciences (TWAS) for the advancement of science in developing countries, and especially for the award of CIIT-TWAS Postdoctoral Fellowship through which this piece of work was possible. They are also thankful to Pakistan Science Foundation (PSF/NSFC-Earth/C-COMSATS-lsb (07)), National Natural Science Foundation of China (41661144024) and the Higher Education Commission of Pakistan (8035/Balochistan/NRPU/R&D/HEC/2017). They would like to thank HavestChoice for providing the valuable datasets that formed the basis for this research. The authors would also like to thank the anonymous reviewers and the editor for their valuable comments and suggestions to improve the quality of our manuscript.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Amara, D.M.K., Ullah, K. & Yushu, Z. Rainfall erosivity estimation for Sierra Leone using non-parametric indices. Theor Appl Climatol 139, 221–236 (2020). https://doi.org/10.1007/s00704-019-02960-3
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00704-019-02960-3


