Heavy rain risks are only one possible environmental risk.

Spatial and holistic concepts need to take various sectoral plannings and aspects of climate adaptation and protection into account. The reduction of heavy rain risks is only one planning criterion for the selection of water management oriented precautionary measures. In addition to heavy rain events, heat stress, the duration of droughts and the intensity of storms are expected to increase in the future. Ideally, measures are selected in such a way that synergies can be exploited and a measure is suitable for adapting to different impacts of climate change (for example green roofs support the retention of rainwater but also reduce heat).

On the other hand, conflicting objectives between different fields of action need to be balanced in planning decisions as early as possible.

Since heavy rain is a rather local event, and consequences depend very much on local characteristics, good local spatial planning can account best for suitable and effective heavy rain risk mitigation measures, e.g. through municipal zoning plans. Spatial planning at local and regional levels must be well coordinated to reduce heavy rain risk and meet the new challenges of climate adaptation.

Area-related planning measures to reduce the risk of heavy rain should be taken into account in new (urban) developments. Planning and design possibilities to safely steer surface runoff and avoid damages are more effective and easier to implement than adaptation measures in existing settlements. For example, it is easier to keep flood-prone areas free of e.g. buildings or to allow only flood-resistant buildings than to adapt existing settlement structures (reducing sealed surfaces, house protection, etc.).

Heavy rain risks can be taken into account in spatial planning by means of both formal and informal planning instruments. Formal, legally binding instruments create the necessary planning security. They must be developed in such a way that they can mitigate the effects of climate change through risk reduction and adaptation measures in the various fields of action. Informal approaches, on the other hand, tend to promote creative solutions and therefore offer a good opportunity to introduce new variants and alternatives.

Spatial planning determines the long-term use and function of spaces, and therefore has to take many future uncertainties into account, such as demographic changes, energy system transformation, and climate change. Today’s good practice spatial planning decisions may become unfavorable in the future, when unforeseeable climate change effects may significantly impact the quality of life. Therefore, more flexibility must be created for the changing environmental conditions, in order to reduce the vulnerability of regions and settlements and improve the quality of life through adaptive planning methods.

Consequently, planning processes and instruments should be kept flexible to establish a chain of successive strategic decisions with possibilities to develop binding effects rather than drawing up one comprehensive plan with final statements.

Climate change and its consequences, like increasing heavy rain risks, are an important issue and affect ecological as well as social and economic aspects of spatial development. Cities, settlements, roads, railways and waterways as well as supply and disposal infrastructures may be affected. Long-term spatial planning decisions are made for these land uses. The decisions made in the past regarding today’s land uses should be reviewed critically and reconsidered with regard to the necessary adaptations to climate change.

Planners must communicate risks as well as opportunities for the city or region to the stakeholders concerned. This should be done as early as possible, in order to create a common level of understanding, to coordinate different goals and to involve them in the planning processes. Appropriate cooperation and coordination mechanisms must be established for the implementation of risk reduction measures.

Given the likely magnitude of the adjustment challenges, it is important to work to safeguard resources and finances. Local authorities in particular need support. The proposed risk reduction measures are often not standard procedures, so that the necessary budget and the effect of the measure are often not known exactly. The results of cost-benefit analyses can therefore provide a good basis for the prioritisation of financing options.