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