Hydropedological Assessment of Soil-Water Retention Proxies in Semi-Arid Tectonic Watersheds of Eastern Indonesia: Landscape–Soil Profile Controls

Maintaining soil moisture conditions in the vadose zone is crucial to maintaining water availability in a semi-arid environment. However, understanding of biophysical factors related to soil moisture conditions in the Wallacea tectonic landscape remains limited. This study presents results from a proxy-based hydropedology assessment that correlates landscape attributes with soil profile characteristics in the Noelmina, Benain, and Walanae watersheds. Data covering elevation, slope, effective depth, soil texture, and horizon sequence were collected through a semi-detailed soil survey at 125 observation points. Data were analyzed using spatial characterization, Spearman rank correlation, and Random Forest modeling. through profile physical properties as an operational proxy, rather than through direct laboratory measurements of hydraulic parameters. The results showed that the relationship between landscapes and soil profiles varied across watersheds. In contrast, effective soil depth consistently showed the highest relative predictive contribution to texture class variation (0.386 in Noelmina, 0.463 in Benain, and 0.501 in Walanae). This study demonstrates landscape-conditioned soil profile functions that link geomorphic context to physical profile properties relevant to water storage and redistribution. These results provide empirical evidence for proxy-based hydropedological control and form the basis for assessing site-specific land-water resources in semi-arid tectonic watersheds.