RO-R-3: Priority and restricted areas for (preventive) flood control | Umweltbundesamt

RO-R-3: Priority and restricted areas for (preventive) flood control

In the period of 2009 to 2013, the terrain of priority and restricted areas for (preventive) flood protection underwent a distinct increase by approximately 4,000 square kilometres. By end of 2017, 88 of 114 regions had incorporated relevant specifications in their regional plans.

Safeguarding areas for inland flood protection

One potential consequence of climate change might be a change in the frequency and severity of flood events, for example when incidents of heavy rainfall in summer intensify or when precipitation in winter increases or when it more frequently falls as rain. In winter months soils saturated with rain can absorb only very little precipitation. Consequently, this precipitation is usually almost immediately added to run-off. Consequently, provident flood protection is an important measure for the adaptation to impacts of climate change.

The designation of flood plains, as covered by binding regulations embedded in the nationwide WHG, is therefore a key component of preventive flood protection. It is the remit of competent authorities to designate flood plains within areas perceived to be at risk thus ensuring that they are available for flooding in case of a so-called 100-year flood event. Furthermore, areas such as flood polders and flood channels have to be included in this designation to serve as flood relief spillways.

However, over and above any legal regulations, it is the remit of spatial planning to use its own tools for contributing to preventive flood protection. An essential element of the planning toolbox available for this purpose is the use of spatial planning specifications on flood protection. These can be used to govern spatial utilisation in a way to make an area less vulnerable to flood risks which – judging by experience – are expected to increase as a result of climate change. Any areas at risk can be precluded from utilisation as settlement or infrastructure areas. Areas of importance for water retention in the landscape and for provident flood protection with a view to climate change can be safeguarded by means of imposing usage restrictions.

The most significant spatial planning tool for this purpose is the designation of priority areas for preventive flood protection. In areas covered by this category of designation, flood protection has priority. Types of spatial utilisation incompatible with this purpose are precluded. So far the practice of designating priority areas has been generally heterogeneous among planning regions.

However, usually it is based on the demarcation of legally recognised flood plains. In some cases, specifications are included in regional plans as memoranda, in others the designated priority areas are identical with specified flood plains, while in some other regions priority areas go beyond the demarcations of flood plains. In some cases, however, legal regulations expressly preclude priority designations by spatial planning authorities, as for instance in the ‘Doppelsicherungsverbot’ embedded in Bavaria’s State Planning Act.

As stipulated in WHG regulations, the specification of flood plains had to be completed by 2013. As was to be expected, however, numerous planning regions have had to carry out a first-time or renewed designation of priority and restricted areas at a later date. By 2017, the terrain of priority and restricted areas comprised approximately 11,800 square kilometres in planning regions overall. Since 2009, 11 of 114 planning regions included new relevant designations in their regional plans, thus increasing the terrain of priority or restricted areas reserved for preventive flood protection by 4,330 square kilometres in Germany nationwide. The majority of new designations were carried out by 2013.

In the light of the impending adaptation to the impacts of climate change it seems sensible – where appropriate – to strengthen spatial planning designations for preventive flood protection by going beyond the legal specification of flood areas thus reinforcing the precautionary intention. In past years, various modelling projects of spatial planning examined relevant options. In the region of Oberes Elbtal-Osterzgebirge, for example, a new methodology was developed for designating priority and restricted areas for preventive flood protection. This methodology was subjected to legal scrutiny, including the demarcation of priority areas for preventive flood protection in terms of risk intensity (water depth and flow rate) during extreme flood events thus also including the extent of settlement. The outcomes are taken into account by the planning region in the current overall update of their regional plan and will be incorporated as implementation-oriented recommendations for action.

Interfaces

WW-I-3: Floodwater

RO-R-6: Settlement use in flood-risk areas - case study

Objectives

Reinforced protection against increasing flood risks by  means of passive safeguarding measures, especially in terms of keeping out development; safeguarding existing run-off and retention areas as well as provident planning for expanding such areas in case of 200-year flood events; substantial expansion of retention areas by 2020 (DAS, ch. 3.2.14)

Safeguarding existing flood plains as retention spaces; restoration of flood plains as retention spaces; risk provisioning in potential flood areas; enhancement of water retention in the catchment area of rivers; safeguarding potential locations for flood protection measures (Handlungskonzept Klimawandel, MKRO 2013, ch. 3.1)

Preventive inland flood protection, especially by means of safeguarding or restoring alluvial meadows, retention areas and flood relief spillways (ROG, § 2 (2) 6)