A sediment influx-outflux-accommodation composite index-based method for estimating sediment storage in debris flow channels

The distribution of the sediment material storage quantity along the debris flow channels (SMSQ_DFC) can provide a foundation for runoff-generated debris flow prediction or susceptibility assessment. Current models for estimating SMSQ_DFC do not consider the capacity of the channel cross-section to accommodate sediment materials. This accommodation condition serves as a limiting factor in determining whether the expected surplus of sediment materials can ultimately be stored. To address this issue, a mass-conservative index was used to represent the balance of deposit materials at any cross-section, considering the influx from upstream, outflux to downstream, and accommodation capacity. Based on this index, a new model for estimating SMSQ_DFC was developed and subsequently evaluated. The evaluation results show that the model meets the accuracy requirements with average error rates of 14.06% for self-validation and 14.81% for generalization ability validation. To assess its practical applications, the model was applied to the Yeniu Gully in Wenchuan County, Sichuan Province, an area with detailed field survey data. The results show that the model exhibits a commendable performance. Compared to traditional theoretical and semi-theoretical statistical models, our model is easier to use (input parameters can be obtained using Geographic Information Systems (GIS)). The modeling parameters chosen in this study have more theoretical significance than those used in existing purely statistical models, offering more effective technical support for estimating SMSQ_DFC.