Changes in sediment discharge in a sediment-rich region of the Yellow River from 1955 to 2010: implications for further soil erosion control

The well-documented decrease in the discharge of sediment into the Yellow River has attracted considerable attention in recent years. The present study analyzed the spatial and temporal variation of sediment yield based on data from 46 hydrological stations in the sediment-rich region of the Yellow River from 1955 to 2010. The results showed that since 1970 sediment yield in the region has clearly decreased at different rates in the 45 sub-areas controlled by hydrological stations. The decrease in sediment yield was closely related to the intensity and extent of soil erosion control measures and rainstorms that occurred in different periods and sub-areas. The average sediment delivery modulus（SDM） in the study area decreased from 7,767.4 t/（km^2·a） in 1951–1969 to 980.5 t/（km^2·a） in 2000–2010. Our study suggested that 65.5% of the study area with the SDM below 1,000 t/（km^2·a） is still necessary to control soil deterioration caused by erosion, and soil erosion control measures should be further strengthened in the areas with the SDM above 1,000 t/（km^2·a）.

Responses of flood peaks to land use and landscape patterns under extreme rainstorms in small catchments-A case study of the rainstorm of Typhoon Lekima in Shandong,China

Investigations of the formation mechanisms of flood peaks in small catchments facilitate flood prediction and disaster prevention under extreme rainstorms.However,there have been few studies on the re-sponses of flood peaks to land use landscape patterns using field surveys during extreme rainstorm events.Based on field data from 17 small catchments near the rainstorm center of Typhoon Lekima,7 landscape indices were chosen.The flood peak and its sensitivity to the land use landscape were investigated by combining remote sensing interpretation and related analysis.The conclusions are as follows:(1)The peak discharge of the small catchment was 2.36e56.50 m3/s,the peak modulus was 8.00 e48.89 m3/(s$km2),and the flood index K ranged from 3.61 to 4.55.(2)Under similar rainfall conditions,the flood peak modulus,K and the proportion of sloping cropland had significantly positive correlations(p<0.05).The flood peak modulus was significantly negatively correlated with the proportion of forest-grassland and terrace(p<0.05),and K and the proportion of forest-grassland and terraced land exhibited a negative correlation.(3)The flood peak modulus and K were positively correlated with the landscape fragmentation.(4)The sensitivities of small catchments to floods were evaluated to be moderate compared to K values from other studies.The ability of small catchments to cope with extreme rain-storms can be improved by increasing the areas of forest-grassland,and terraces and reducing landscape fragmentation.Our results could be applied to provide a basis for land use planning and support for the response against disasters caused by extreme floods.