Hydrological responses on saline-sodic soil slopes in a coastal reclamation area of China

• Factors affecting overland flow velocity on saline-sodic soil slopes were studied.
• Flow hydraulic parameters predicting sodic sediment transport were compared.
• Mean flow velocities and stream power values tended to increase on steeper slopes.
• Stream power was a better predictor than hydraulic shear stress of sediment loss.
• The effects of sodicity with salinity on erosion processes require more attention.

Evaluation of the effects of slope gradient and rainfall intensity on the hydrological responses on slopes can provide important information for soil and water conservation. We conducted simulated rainfall experiments to study the hydrological response of a saline-sodic soil on slopes with different gradients (6°, 11°, 22°, and 35°) and rainfall intensities (85, 95, 110, and 125 mm h− 1). Higher effective rainfall intensities significantly reduced the times to ponding and runoff. While the infiltration coefficient did not always increase with increasing slope gradient, it consistently increased with increasing rainfall intensity on slopes of 6°, 11°, or 22°. The mean flow velocities and stream power values tended to increase with increasing slope gradient but did not change consistently with changes in rainfall intensity. Hydraulic shear stress and its logarithm could predict sediment losses that were < 20 kg m− 1 h− 1. However, stream power and its logarithm were better predictors of a wider range of sediment losses from slopes with saline-sodic soil. These results suggest that existing hydrological and erosion models should be adjusted to take into account the effects of salinity and sodicity.