Throughout Europe, there is a considerable need for investment in the upgrade of sewer systems – due to three main factors: ageing infrastructure, climate change and urban population growth. The need for investments is expected to grow significantly in the years ahead. Trenchless rehabilitation (no-dig) of sewer pipelines is a cost-efficient and environmental friendly method for upgrading existing pipelines with sufficient capacity. This study examines the possibility of applying no-dig to combined sewer systems (CS) with insufficient capacity. In this study an concept assessment methodology that combines the analytical approaches from stormwater and sewer system assessments is presented. The methodology was tested on a case area that was part of an environmental project in Oslo, Norway. Three alternative concepts were examined; A0: no-dig and low impact development (LID), A1: no-dig, LID and green infrastructure (GI), and A2: CS up-sizing using open-cut methods. The study concludes that CS with insufficient capacity can be rehabilitated using no-dig if LID and GI. The combination of no-dig and LID reduces costs considerably but does involve the risk of damages from uncontrolled surface runoff. The main risk-reduction measure is the development of GI as an integrated stormwater management system that requires cross-sector collaboration within municipalities.

A number of cost-effective and environmentally friendly flood reduction measures can provide detention of runoff from natural landscapes upstream of urban areas, with multiple added benefits. This study presents a methodology for assessing the needs for and feasibility of natural flood detention facilities. The candidate catchments for natural flood detention facilities were identified by GIS analysis and further assessed using data from maps and field inspections. Results for two case catchments show that a suitable topography and nature and biodiversity are key feasibility criteria for natural flood detention facilities. The study concluded that it is possible to streamline the process of selecting the location and type of natural flood detentions facilities. Map analyses, field inspections and interdisciplinary collaboration are all important when planning natural flood detention facilities. As a result of the study, the City of Oslo will construct several natural flood detention facilities upstream of the city to gain practical experience with such facilities. While it is not expected that natural flood detention will solve all flooding problems in urban areas, it is expected that natural flood detention can positively contribute to future resilient stormwater management and the implementation of the EU Strategy on Adaptation to Climate Change.

One of the effects of climate change is an increasing frequency of heavy rainfall events, which in turn leads to increased flooding damage in urban areas. The purpose of this study was to develop a tool for dynamic risk evaluation that can be used to fulfil several of the goals in the European Flood Risk Management Directive. Flood risk analysis was performed as a spatial GIS analysis with the FME software. The primary data source for the analysis was a 1D/2D model calculation, wherein 1D models described the pipeline network and the watercourses and a 2D model described surface runoff. An ArcGIS online platform was developed to visualize the results in a format understandable for decision makers. The method and tool were tested for the Norwegian capital of Oslo. The tool developed in the study enabled the efficient analysis of consequences for various precipitation scenarios. Results could be used to identify the areas most vulnerable to flooding and prioritize areas in which measures need to be implemented. The study showed that for urban areas in steep terrain, it is essential to include water velocity and depth-integrated velocity in risk analysis in addition to water depths and pipe network capacity.