Change in riverine suspended sediment concentration in central Japan in response to late 20th century human activities

摘要: Abstract The effects of human activities on suspended sediment concentration (SSC) during the late 20th century were examined at 57 sites along major rivers in central Japan using governmental data and GIS. Analysis relationships between mean SSC catchment properties, such as land use, has revealed that patterns concentrations these are primarily linked to agricultural land, construction work, domestic industrial effluent sources populated areas, whereas natural erosion steep areas plays only a limited role. This observation contrasts with abundant bed load supply due mountainous Japan. Measurements, made over approximately 20 years, indicate majority measurement underwent decreases time. In contrast, river discharge tended be constant, indicating fine decreased last two decades. reflects reductions area urbanisation, well water pollution control mitigation measures introduced since 1970s. At quarter sites, however, constant or even increased. Many experienced high rates population growth decades, increases increased activity obscured decreasing trend SSC. temporal change western Tokyo was also affected by artificial landform transformation.