Reassessing runoff coefficients for flexible pavements in Ecuador: correlations with macrotexture, moisture and a novel double-ring infiltrometer approach

Abstract This study analyzes the relationship between surface macrotexture, retained moisture, and runoff coefficient (C) in flexible pavements from Ecuador’s Inter-Andean region. The research forms part of the project “Use of Andean Materials in the Design of Sustainable Permeable Pavements in Ecuador” developed at the Universidad Nacional de Chimborazo (UNACH). Seventeen sites located between 2,668 and 4,359 m.a.s.l. were evaluated through laboratory tests, while twenty-two sites were assessed in the field. Infiltration and runoff fractions were quantified using the patented UNACH Double-Ring Infiltrometer, and moisture content and surface macrotexture were determined through core sampling and the Sand Patch Test. Regression analyses revealed strong correlations (R² = 0.81 and 0.94), showing that higher macrotexture values were associated with increased runoff and lower moisture retention, likely due to pore clogging by fine sediments and microplastics. The measured runoff coefficients (C > 0.97) exceeded Ecuadorian standard values (0.85–0.90), indicating a potential underestimation of design stormwater flows. The results highlight the need to update national design parameters to account for material evolution, climatic variability, and pavement aging, supporting the development of permeable pavements that improve infiltration and promote sustainable stormwater management.