Abstract
Assessment of the impacts of land use/cover change (LUCC) and rainfall change on surface runoff depth can help provide an understanding of the temporal trend of variation of surface runoff and assist in urban construction planning. This study evaluated the impacts of LUCC and rainfall change on surface runoff depth by adopting the well-known Soil Conservation Service-Curve Number (SCS-CN) method and the widely used Long-Term Hydrologic Impact Assessment (L-THIA) model. National hydrologic soil group map of China was generated based on a conversion from soil texture classification system. The CN values were adjusted based on the land use/cover types and soil properties in China. The L-THIA model was configured by using the adjusted CN values and then applied nationally in China. Results show that nationwide rainfall changes and LUCC from 2005 to 2010 had little impact on the distribution of surface runoff, and the high values of runoff depth were mainly located in the middle and lower reaches of the Yangtze River. Nationally, the average annual runoff depths in 2005, 2010 and 2015 were 78 mm, 83 mm and 90 mm, respectively. For the 2015 land use data, rainfall change caused the variation of surface runoff depth ranging from −203 mm to 476 mm in different regions. LUCC from 2005 to 2015 did not cause obvious change of surface runoff depth, but expansion of developed land led to runoff depth increases ranging from 0 mm to 570 mm and 0 mm to 742 mm from 2005 to 2010 and 2010 to 2015, respectively. Potential solutions to urban land use change and surface runoff control were also analyzed.
Highlights
Urbanization in China has attracted wide international attention in recent years [1]
Influenced by the land use/cover change (LUCC) and rainfall change in the last 15 years, depths were located in the Yellow River basin and southwest China, and the middle values of runoff depths were located in northwest, northeast and the south coast of China
The Service-Curve Number (SCS-CN) method and Long-Term Hydrologic Impact Assessment (L-THIA) model were used to assess the impact of LUCC and rainfall change on surface runoff depth from 2005 to 2015 in China
Summary
Urbanization in China has attracted wide international attention in recent years [1]. An increase in developed land usually means growth of impervious surface area, which is regarded as the direct cause of urban surface runoff [4,5,6]. Urban flooding occurred on average in 185 cities per year from 2010 to 2016 in China; especially, in 2016, a total of 192 cities above the county level suffered floods, which caused direct economic losses amounting to 548.49 billion dollars [7]. Due to the increase of impermeable surfaces, surface pollutants enter water bodies with surface runoff, which increases the risk of non-point source pollution and leads to water quality degradation [8,9,10,11]. Apart from the increased impervious surface area, another main cause of urban flooding is rainfall change. Research shows that precipitation in the eastern part of China presents a large increase, while a large decrease occurred in the central region and a small increase occurred in the west from 1961 to 2010 [12]
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