Automatic mapping of urban wastewater networks based on manhole cover locations

Accurate maps of wastewater networks in cities are mandatory for an integrated management of water resources. However, in many countries around the world this information is unavailable or inaccurate. A new mapping method is put forward to create maps using manhole cover locations which could be available via ground surveys, remote sensing techniques or stakeholder's databases. A new algorithm is developed which considers manhole covers as the nodes of the network and connects them automatically by minimizing cost functions defined by industry rules thus generating an optimized network. The various input data and rules used to build the deterministic tree-shaped graph being uncertain, a stochastic version of the algorithm is also proposed to generate a set of probable networks in addition to the optimized one. The method is tested on the wastewater networks of Prades-le-Lez and Ramnonville Saint Agne, two towns located in Southern France. The shape and topology of the mapped networks are compared to the actual one. The results indicate an overall good agreement between the real and generated networks. The proposed algorithm may thus be used to map wastewater networks from sampled georeferenced manhole covers, elevation and street network databases. •A new optimization algorithm that connects manhole covers to build a tree-shaped urban wastewater network is proposed.•The algorithm optimizes a directed subgraph while respecting industry, topological and topographical rules.•Stochasticity in the algorithm allows to propagate uncertainties due to input data and rules into the map.•The network generated using the algorithm shows good agreement with the actual network of the study zone.•The algorithm is generic and efficient and may be used in cities with limited urban databases.