Tracing sediment sources in a plain river network area by using optimized experimental design and reflectance...

Area of Science:

• Environmental Science
• Hydrology
• Soil Science

Background:

• Soil erosion in plain river networks leads to siltation, non-point source pollution, and eutrophication.
• Traditional sediment tracing methods are often unsuitable for complex plain river systems.
• The environmental impact of sediment in these areas is substantial and requires effective tracing techniques.

Purpose of the Study:

• To develop and validate a sediment tracing scheme specifically for plain river network areas.
• To quantitatively distinguish the types and contributions of different sediment sources in a typical plain river network.
• To identify the primary factors influencing sediment sources in the study area.

Main Methods:

• Analysis of flow structure and characteristics in a typical plain river network (Taihu Basin).
• Development of a stream segment sampling scheme and a two-step sediment tracing model.
• Application of discriminant function analysis and Random Forest models for source apportionment using soil spectra.

Main Results:

• Discriminant function analysis showed high accuracy (R²=0.96) for basin soil contribution.
• Random Forest model provided better discrimination for different land types (farmland, forest, grassland) with R² values of 0.89, 0.83, and 0.80, respectively.
• Average soil proportion in sediment was 23%, increasing downstream; major sources identified were grassland (44%), forest (39%), and farmland (42%) for specific rivers.

Conclusions:

• Land-use distribution, water conservation facilities, and soil particle size are key factors affecting sediment sources.
• Targeted pollution control measures, optimized soil conservation, and regular silt removal are recommended to mitigate sediment impacts.
• The developed tracing method is effective for plain river networks, aiding in environmental management and pollution control.