Abstract: Flash flood and debris flows represent typical soil-water coupled surface processes，whose formation and evolution involve multi-scale and multi-process interactions including rainfall infiltration，slope destabilization，gully erosion，and solidliquid two-phase flow dynamics. Establishing systematic observation indicator systems and technical methodologies constitutes the critical foundation for deepening mechanistic understanding and enhancing early warning capabilities. This paper systematically reviews advancements in observation indicator frameworks and technical approaches for soil-water processes in flash floods and debris flows. The evolution of observation indicator systems has progressed through four distinct phases：from single hydrological elements，to sediment transport processes combined with dynamic parameters，then to multi-process coupling integration，and finally to multi-source data fusion with intelligent early warning systems. Observation techniques have transitioned from manual monitoring toward integrated multi-technology collaboration systems combining ground-based sensing， remote sensing surveillance，and intelligent algorithms，forming a comprehensive observational framework encompassing meteorological and hydrological conditions，hillslope soil-water states，channel sediment transport processes，and flow dynamics. Through comparative analysis of representative small watershed observatories globally，three generational paradigms have emerged：engineering prevention-oriented，mechanism analysis-oriented，fullchain coupling，and data openness-oriented. On this basis, proposing key bottleneck issues Current challenges in observation systems include complexities in multi-scale coupling，difficulties in capturing soil-water interface processes，insufficient analysis of solid-liquid two-phase flow mechanisms，and lack of data standardization. Future research should prioritize integrated "air-space-ground" integrated stereoscopic detection，distributed fiber optic sensing，edge computing，and digital twin technologies to establish standardized， intelligent observation frameworks that support mechanistic studies and precise early warning of flash flood and debris flows.