Study on Sustainability of River Training Structures with Special Reference to Ratuwa Khola, Jhapa, Nepal

Abstract

River training structures are essential for flood mitigation and bank protection in dynamic alluvial rivers, and this study assesses their sustainability along a selected reach of the Ratuwa Khola in Jhapa, Nepal. Thirty structures (17 right-bank, 13 left-bank) were systematically inventoried and evaluated using field inspections, descriptive statistics, Pearson correlation analysis, multiple regression analysis, focus group discussions with 12 community members, and in-depth interviews with four institutional informants. About 65–70% of the structures are in good condition, while the remainder exhibit distress settlement, erosion, and cracking concentrated in hydraulically vulnerable reaches. Statistical analysis identified channel stability as the strongest predictor of structural performance (r = +0.521, R² = 0.271), and riverbed material extraction as a significant anthropogenic stressor with a negative effect (r = −0.373, R² = 0.139); sediment type showed only a weak relationship with condition (r = +0.027, R² = 0.0007). The multiple regression model was statistically significant (F (4,25) = 3.677, p = 0.017) and explained 37.0% of the observed variance in structural condition (adjusted R² = 0.270). Waterway width and channel stability showed positive coefficients, while quarry activity showed a negative coefficient. Nevertheless, none of the individual predictors reached statistical significance at the 5% level, indicating that structural performance is likely governed by the combined effects of hydraulic and morphological processes rather than by any single factor. In particular, the relatively stronger association of channel stability with structural condition suggests that local scour, channel migration, and bank instability may represent critical mechanisms controlling the deterioration of river training structures. Vegetation cover influenced outcomes qualitatively, with plantations supporting better performance and grass-dominated areas showing greater vulnerability. Qualitative findings have revealed institutional weaknesses no post-construction monitoring, reliance on hydrological data from a gauge decommissioned in 2011, fragmented financing that delays maintenance by 6–12 months, and continued use of rigid, colonial-era design standards unsuited to the river’s braided form. Community members reported downstream erosion and agricultural land loss linked to upstream spur construction, while institutional respondents recommended mandatory structural audits, a dedicated maintenance fund, and updated climate-adjusted design codes to improve long-term sustainability.