Miljøprojekt, 1123 – Afløbssystemer under påvirkning af klimaændringer - Hovedrapport

Afløbssystemer under påvirkning af klimaændringer - Hovedrapport

Summary and conclusions

In Denmark three climate change scenarios have been selected for the analyses related to climate changes, i.e. A2, B2, and EU2C. The likely occurrences of three scenarios are considered to have an equal probability.

The Danish EPA has initiated a proactive investigation on how the Danish municipalities in a cost efficient way, can mitigate the impact of climate changes on sewer systems. The management and mitigation of the impacts of climate changes demand a holistic and integrated planning process across departments in the municipalities, as more types of legislative procedures will be affected compared to today’s work flow.

Analyses of the expected climate change scenarios have revealed that the number of high intensity rain fall events will increase during the summer and that the mean sea level in the Danish waters will increase as well. Both of these phenomena may have an influence on the performance of the sewer systems and hence their impacts must be clarified through analyses.

Estimates of impacts from climate changes are proposed to be carried out on three levels. After the impact assessment, the problems should be prioritized e.g. by use of risk assessment tools. Based on the findings the municipalities must develop a plan for timely management and mitigation of the impacts from climate changes. The plan should contain descriptions of how and when climate changes are analysed and managed for:

• Planning and design of new sewer systems.

• Existing sewers where maintenance and reconstruction are already planned.

• Existing sewers where no maintenance and reconstruction are scheduled today.

A case study (based on a real project) has been carried out for a catchment in the city of Odense, Denmark. The case study illustrates the impacts in terms of flooding from potential climate changes (Scenario A2). Further, it demonstrates analyses of a flood mitigation strategy for the catchment.

The strategic decision from the Danish EPA to develop a mitigation strategy for climate changes has resulted in a set of guide-lines for the Danish municipalities. This set of guide-lines provide the Danish municipalities with the means to develop a timely and cost efficient strategy for coping with climate changes and their impacts on sewer system.