Effect of Pipe Roughness on Optimal Sewer Networks with Drop Manholes in Steep Terrains

The present work aims to investigate the effect of pipe roughness on the construction cost of sewer networks in steep terrains. To achieve this objective, a sensitivity analysis was performed, wherein a sewer network was designed with different pipe roughnesses and varying terrain slopes to simulate four distinct steep terrains. In addition, this study considers the effect of new pipes with very high roughnesses that have appeared on the market in recent years, evaluating their influence on sewer network design and construction cost in steep terrains. The sewer networks were designed using an existing methodology for an optimal design that includes drop manholes if required to meet all the hydraulic constraints. The effect of pipe roughness was tested in two sewer networks from distinct sectors of Bogotá, Colombia.

This study has relevance when considering its ability to lead to the expansion of the sewer service, particularly in hilly regions. The use of higher roughness pipes as a result of this finding has a direct impact on reducing the need for drop manholes, leading to a significant reduction in associated costs. This reduction in costs is of paramount importance in the viability and execution of sewer projects in communities facing significant financial constraints. By minimizing costs, this approach not only optimizes project efficiency but also facilitates access to basic sanitation services in geographic areas previously considered difficult to address. Consequently, this research not only improves sewer systems but also contributes to community development.