Effects of Geographic Accessibility and Mahakam River’s Water Levels on HSBGN in Mahakam Ulu Regency

Abstract

Public building unit costs in Mahakam Ulu Regency depend on river-based logistics and unequal geographic accessibility. This study reanalyses the 2025 final-report dataset to quantify differences across four accessibility zones and two river-water conditions. The analytical sample comprises 64 public building unit-cost entries (eight building or fence typologies × four zones × two conditions), 36 material-price observations, and recorded freight tariffs. Paired comparisons identify a highly consistent low-water correction coefficient of 1.2083, equivalent to a 20.83% premium over the normal/high-water scenario. Mean geographic indices relative to Zone I are 1.1411, 1.2799, and 1.4916 for Zones II, III, and IV, respectively, although indices vary by building typology. Across the comparable transport routes, listed low-water freight tariffs are approximately 25% higher than normal-water tariffs. The results yield a transparent two-factor indexing scheme for preliminary budgeting; however, the coefficients are descriptive ratios of an existing cost matrix, not independently validated causal effects. The source documents do not provide complete point-to-point distances, so a rupiah-per-kilometre coefficient cannot be justified.