Department Urban Water Management

Sustainable Network Infrastructure Planning (SNIP)

Picture 1: Scattered Settlements challenging network based infrastructure planning
(Source: Wikipedia)

The aim of this project is to gain more insight about sustainable infrastructure management and to develop tools and methods for complex decision making for infrastructure planning.

Within this project the focus lies especially on challenges for network based infrastructure types. One such example is today's waste water system. In today planning practice of extending the existing network the question is rarely raised whether always simply extending is the most sustainable option. The optimal dimensioning and geographic distribution of waste water treatment plants becomes especially challenging if taking in consideration future uncertainties like for example the settlement distribution. For a sustainable investment and infrastructure planning of network-based infrastructure tools are needed for deciding about the optimal distribution of centralized and decentralized infrastructures.


Life without the variety of today’s network based infrastructures is hardly imaginable. Examples are for example streets networks, waste water and water networks or heating related networks (gas, electricity or district heating). Nonetheless the construction and operation of these important infrastructures is very capital intensive for the generation today and tomorrow.
One such example is the Swiss waste water system. In Switzerland, in most cases the waste water flows in a sewer network to a central treatment plant. Decentralized, not net-bound small scale treatment plants (e.g. on-site treatment plants) hardly play a significant role. Depending on the local topographic and settlement structures the economic efficiency of the centralized system is different. The advantages of a more decentralized solution are savings due to the absence of large pipes. In planning and maintaining today's waste water system the question is whether as well alternative, not-net bound solution make more sense from an economical point of view.

The question about an economically sustainable infrastructure development must be addressed in rapidly changing environments. New technologies, changing costs, uncertainties concerning the settlement and changes in the population development lead to a complex decision making situation. The external framework and initial conditions are very different depending on the geographic situation. An improved understanding of these relationships is important for the understanding of sustainability transitions.


Geographic information systems are interesting for modelling an economic optimal distribution of infrastructures due to the strong spatial connection of the research questions. With help of heuristics a network algorithm is used to simulate an optimal network. The aim of the used methodology is to be able to find robust statements about today's and tomorrows optimal distribution and dimensioning of the waste water system.

Project Focus

The questioned raised in this project shall be tested with help of different case studies with different preconditions in Switzerland and abroad.

Main focus:

  • The development of a generic model for estimating the optimal penetration rate of decentralized and centralized infrastructures.
  • Explicitly taking in account uncertainties such as the future settlement- and population distribution.
  • Demonstrating sustainable infrastructure planning in  different contexts with help of case studies.