Background The Rizhao City, located in the southern coast of Shandong province, is northern rocky mountain soil and the national key harnessing area of Yimeng Mountains and Taishan Mountain, China. However, there are few studies on the soil erosion in the region, and no detailed research on the rainfall erosivity has been carried out specifically for Rizhao City scale.

Methods In order to investigate the spatial and temporal variations of rainfall erosivity in Rizhao City and improve the scientific nature of soil and water conservation planning and decision-making, we used the daily rainfall data of 61 rainfall stations in Rizhao City from 2005 to 2014 to calculate the rainfall erosivity by the daily rainfall erosivity model, and analyzed the spatial pattern with the help of ArcGIS10 and the temporal variation and the correlation between rainfall, erosive rainfall and rainfall erosivity by virtue of Excel 2013.

Results 1) For the temporal variability, the annual rainfall erosivity ranged from 1 831.55 MJ·mm/(hm²·h·a) to 5 306.12 MJ·mm/(hm²·h·a), the maximum value(2008) of the average annual rainfall erosivity was 2.90 times of the minimum (2014), and the maximum value (2007) of the rainfall erosivity in flood season was 3.74 times of the minimum (2014). The monthly rainfall erosivity per station was in the range of 1.23 MJ·mm/(hm²·h·a) to 1 171.93 MJ·mm/(hm²·h·a), the rainfall erosivity was concentrated from May to September, especially from July to August. 2) For the spatial variations, the average rainfall erosivity yearly and in flood season generally increased from inland areas to southeast coastal areas, and the lowest in the central region. Comparing them at the county scale, the highest of the average annual rainfall erosivity was in Lanshan, and then Donggang, the lowest was in Juxian and Wulian. The average annual rainfall erosivity in each station was from 2 755.23 MJ·mm/(hm²·h·a) to 5 061.15 MJ·mm/(hm²·h·a), the average and the median was 3 826.01 MJ·mm/(hm²·h·a) and 3 730.97 MJ·mm/(hm²·h·a), respectively, and the standard deviation was 512.81 MJ·mm/(hm²·h·a), and the variability coefficients was 13.40%.

Conclusions The spatial distribution pattern of soil erosion in Rizhao City is not exactly matched with the spatial distribution of rainfall erosivity. In addition to the influence of rainfall erosivity, regional soil erosion is closely related to terrain, soil, vegetation and other factors. To strengthen the research on the comprehensive influence of various factors on soil erosion should be the direction of next step. The results can provide a reference for soil and water conservation planning and decision-making and prediction of soil erosion in Rizhao City.