Hydrogeomorphological influences on sediment quality: insights for watershed management

Sediment quality is crucial for watershed management and soil conservation but poorly understood at the watershed scale in semi-arid regions vulnerable to erosion and degradation. This study examines hydrogeomorphological influences on sediment quality in Ardabil Province, northwestern Iran, a area with varied topography, semi-arid climate, and intense erosion issues. We created a Sediment Quality Index (SQI) from 98 streambed sediment samples, collected via stratified random sampling across gradients of elevation, slope, vegetation cover, and lithology. Samples were tested for nine physicochemical traits: organic matter, potassium, lime, pH, electrical conductivity (EC), sand, clay, silt, And bulk density. These were normalized on a 0–1 scale with “more is better,” “less is better,” or “optimal range” functions and averaged for SQI. Analyses involved redundancy analysis (RDA) for multivariate Links between sediment properties And factors Like elevation, rainfall, vegetation, slope, temperature, erodibility, And stream slope; stepwise regression for SQI predictors; and t-tests comparing sediments to slope soils. RDA showed significant relationships, with the first axis accounting for 15.08% variance. Regression highlighted elevation’s negative effect on SQI (β = -0.393, p < 0.01), signaling coarser, less nutritious sediments at higher altitudes from limited soil and vegetation. Vegetation cover and slope positively correlated (β = +0.235 and + 0.225, p < 0.05), improving quality via organic matter, finer grains, and less runoff. Sediments were mostly sandy-loamy, alkaline (mean pH 7.84), and low-EC, indicating erodibility from grazing and lithology. These insights identify key drivers, filling a global gap and guiding conservation like revegetation and bunding for Ardabil and akin areas.