Construction of Sewer Rehabilitation and Its Consequences: A Case Study of Lalitpur Metropolitan City, Nepal

Abstract

Urban sewerage infrastructure plays a vital role in maintaining public health, environmental sustainability, and the overall quality of urban life. Lalitpur Metropolitan City (LMC), one of the major urban centres in Nepal and home to the UNESCO World Heritage Site of Patan Durbar Square, has been experiencing severe drainage and sewerage-related problems, particularly during the monsoon season. Frequent clogging of stormwater drains, overflow of existing sewer networks, waterlogging, and flooding in areas such as Mahapal and Patan Durbar Square have adversely affected public health, transportation, tourism, and environmental conditions. This study investigates the construction of sewer rehabilitation works and their consequences in Lalitpur Metropolitan City. A mixed-method approach was adopted, involving field observations, questionnaire surveys, in-depth interviews with engineers, contractors, consultants, and local stakeholders, focus group discussions, and review of project reports. Data were collected from 205 respondents and analyzed using descriptive statistics and the Relative Importance Index (RII). The study focuses on rehabilitation works along the core sewer network extending from Lagankhel to Sankhamul, including the heritage-sensitive zones of Patan Durbar Square. The findings indicate that inadequate existing sewer infrastructure capacity was ranked as the most severe problem (RII = 0.89), followed closely by lack of proper planning and design integration, weak institutional coordination, and funding and budget constraints (RII = 0.88 each). Insufficient drain capacity, aging sewer infrastructure, improper road gradients, solid waste disposal into drains, inadequate maintenance, and rapid urbanization were identified as the primary causes of sewer blockage and flooding, while consequences include traffic disruption, damage to infrastructure, environmental pollution, public health risks, and negative impacts on tourism and local economic activities. The study identifies preparation of a comprehensive sewer master plan as the highest-ranked mitigation measure (RII = 0.90), followed by strengthening institutional coordination and securing adequate and sustainable funding mechanisms. The findings underscore the need for combined sewer and stormwater planning, regular maintenance, public awareness, and heritage-sensitive construction practices to reduce flooding and improve urban sanitation in Lalitpur Metropolitan City.