Confidence-Aware Framework for Mapping Satellite-Derived River Reaches to Gridded Routing Networks

Abstract. The Surface Water and Ocean Topography (SWOT) mission delivers reach-scale observations of river water surface elevation, contextualized by the vector-based SWORD database. Assimilating these observations into gridded routing models such as CTRIP is hindered by structural mismatches between object-based river geometries and pixel-based flow networks. We present a global, confidence-aware pipeline that assigns SWORD reaches to CTRIP pixels by combining geometric and hydrological criteria such as intersection, proximity, upstream-area consistency, reach length, and flow-direction alignment into a composite score. Each assignment receives a confidence tier (Tier 1: single; Tier 2: scored; Tier 3: fallback; Tier 4: unassigned), and Tier-2 cases are further refined by a confidence score (high/medium/low). Applied globally at 1/12°, the framework assigns >99 % of CTRIP pixels; the vast majority are resolved either unambiguously (Tier 1) or as high-quality scored matches (Tier 2–High), with no fallback assignments and <0.5 % unassigned. Independent diagnostics based on basin-hash continuity confirm hydrological integrity. Code and outputs (CSV, NetCDF, shapefiles) are openly available and directly usable for assimilation into CTRIP or can be applied to any other gridded river network, providing a reproducible foundation for bridging SWOT observations with global river routing models.