Impacts of Climate Change
Table of Contents
Damage to buildings due to heavy rain and river floods
Besides storms, heavy rain and river floods cause the greatest damage to buildings. While the danger from river floods only exists in the immediate vicinity of a river, heavy rain can occur anywhere. For river floods, early warning is usually possible several days in advance, whereas heavy rainfall can often only be predicted a few hours in advance.
How vulnerable a building is to heavy rain or flooding depends on the settlement structure and the characteristics of the building. In areas with high soil sealing and on slopes, the risk from urban flash floods is particularly high. The areas that could be flooded can be shown in flood risk maps and municipal heavy rain hazard maps.
The most vulnerable part of a building is the basement. The extent of damage depends on the type of use. In addition, the type of materials used influences the extent of damage in the event of an emergency. For example, it plays a role which heat-insulating composite materials were installed. This can determine whether renovation is possible or whether demolition is necessary. Contamination with dirty water or water-polluting substances such as chemicals or oils (e.g. from an oil heating system) also plays a major role. These can lead to a considerable increase in the extent of damage or the costs of remediation.
With regard to heavy rain, insufficient driving rain protection of basement windows or the extension of attics, roof terraces and balconies can lead to higher damage. Low building base heights, insufficiently dimensioned drainage systems and unfavourable roof construction methods can also increase the extent of damage. Heavy rain can damage the facade if there is no roof overhang. The consequences can be felt when water enters the building components and leads to moisture penetration damage. Other factors include the construction method of the exterior wall, the year of construction as well as maintenance, servicing and modernisation of roof and drainage systems.
Indicators from the monitoring on the DAS: Heavy rain in residential areas, Insurance density natural hazard insurance residential buildings
Vegetation in settlements
Public green spaces, urban trees, private gardens as well as green roofs and facades have an important urban climatic function: they cool the city and reduce the heat load for the inhabitants. In contrast to buildings and sealed surfaces, vegetation stores hardly any heat and lawns in particular cool down more quickly at night. In addition, there is cooling through evapotranspiration. During the day, the shade cast by trees is also very important.
Vegetation in settlements not only makes valuable contributions to climate protection and climate adaptation, it is also directly affected by climate change. In particular, multiple stresses due to drought, heat, pests, diseases as well as storms are likely to put further pressure on settlement vegetation.
About 70 per cent of the street trees in Germany are of just six species. These are already exposed to multiple stresses such as abiotic stress factors, diseases and pests, so that their resistance is limited. Drought and heat stress in particular are putting frequently used tree species such as lime and maple under increasing pressure and making them even more susceptible to pests and diseases. Some of the classic urban trees will therefore no longer be able to cope with future demands. Poor site conditions are also further stress factors for street trees, such as a small root space due to soil compaction and sealing, low soil and air quality, and pollutant inputs such as road salt.
Urban climate and heat islands
The urban heat island is a typical feature of the urban climate and describes the effect that it is warmer within an urban area than in the surrounding rural areas. The larger and more densely built-up the city, the greater the heat island effect tends to be. A high degree of surface sealing, few cooling green spaces, low air circulation, dark surfaces, high-rise buildings and heat emissions, for example from traffic and building air conditioning, all contribute to this. As buildings store heat and cool down only slowly, the urban heat island effect is strongest at night.
Urban heat islands can lead to a significantly increased heat load. In addition, the urban heat island effect can amplify the negative effects of air pollutants, especially ground-level ozone. Increasing urbanisation leads to an expansion of urban heat islands in terms of area, which can be expected to increase heat stress for people in urban agglomerations.
In the case of long-lasting high temperatures, indoor spaces can also heat up strongly. This can lead to health risks, especially for older people. High indoor temperatures are particularly relevant for facilities such as retirement and nursing homes, facilities for people with physical and mental disabilities, hospitals, emergency and rescue services, rehabilitation facilities, schools, day-care centres and certain workplaces.
Indicators from the monitoring on the DAS: Heat stress in urban environments and summer heat island effect, Cooling degree days
Further climate impacts
Indoor climate: The increasing number and duration of hot spells will increasingly lead to high indoor temperatures without structural adaptation measures. In addition to increasing heat stress, this can also have a negative impact on air quality and indoor hygiene by encouraging the release of hazardous substances and mould growth.
Times for construction activity: Strong winds, heavy rain, heat and exposure to ultraviolet radiation can increase the risk of accidents and health hazards on construction sites and thus lead to construction interruptions for occupational safety reasons.
Adaptation to Climate Change
Measures to reduce damage to buildings caused by heavy rainfall and river floods
Technical adaptation measures can protect buildings from heavy rain, flash floods and river floods or mitigate their consequences. To prevent water from entering through building openings, for example, upstands in the entrance area, in front of cellar stairs and light wells are suitable. Barrier systems that secure building openings are also suitable for flood situations. Measures for infiltration and water retention, such as green roofs, unsealing and infiltration troughs, retain rainwater for longer and help to prevent flooding at the base of the building. Functioning roof drainage with emergency overflows on gutters, balconies and terraces is just as important as backflow protection for sanitary objects below the backflow level. In flood-prone areas, new buildings should be considered without basements. Safe storage of substances hazardous to water (e.g. oil and chemicals) is also of great importance.
Another important measure is the preparation of heavy rainfall and flood hazard maps. They serve as a basis for planning precautionary and emergency measures for municipalities as well as for informing property and building owners and raising their awareness.
At the political level, adaptation requirements in existing technical standards and regulations in the building sector must be given greater consideration. In addition, building standards are required that take into account the higher frequency and intensity of floods and heavy rainfall events due to climate change. This can help to adapt construction methods or even to refuse building permits on endangered areas.
In addition, instruments of building and planning practice must be further developed. For example, since 2020, measures to adapt to climate change and improve green infrastructure have been important funding requirements in Urban Development Support.
Awareness raising and knowledge transfer regarding climate risks and the existing need for adaptation is also an important building block. This concerns professional associations, such as chambers of engineers, craftsmen and architects, as well as building owners, administrations and tenants.
Indicator from the monitoring on the DAS: Funding for building and refurbishment adapted to climate change
Measures for the adaptation of vegetation in settlements
When planting new urban greenery, ensure that the plants are sufficiently heat and drought tolerant. Municipalities need planning tools and information materials that support the selection of climate-resilient trees. The species composition of urban trees should generally be diversified. New concepts for decentralised irrigation of urban green spaces help to reduce drought stress for plants. This includes, for example, the use of water from rainwater retention basins or the drainage of rainwater from roads, footpaths and cycle paths into plant pits in the sense of the "sponge city" model.
Urban Development Support can be used to strengthen settlement vegetation in a targeted manner. Eligible measures include, for example, the creation or expansion of green spaces, the networking of green and open spaces, the greening of building areas and the increase of biodiversity.
In the course of urban redensification, it is particularly important to take into account the principle of dual inner-city development. In this context, it is important to design the redensification in such a way that existing green spaces are preserved and, if possible, new ones are created.
On a political level, the introduction of standards is conducive, for example regarding tree sizes and soil properties such as rootability and water absorption and water storage capacity. Standards could be based on the green space factor or the biotope area factor, which can already be set when drawing up development plans. Monetising the ecosystem services provided by green spaces and wooded areas can also be helpful. This would increase the visibility of these services and thus also the awareness of their relevance with regard to adaptation to climate change.
Indicator from the monitoring on the DAS: Recreation areas
Measures to reduce the heat island effect
In order to reduce the heat load in cities, it is important to maintain and expand green spaces and urban trees. Green facades and roofs also contribute to cooling and improving the microclimate. The implementation of measures according to the "sponge city" model also has positive effects on the heat island effect: Here, rainwater is stored locally and used for irrigation, for example, instead of being discharged into the sewage system.
To promote such measures, information materials, planning tools and recommendations for action for urban and open space planning are helpful. Urban Development Support provides support with financing. In addition, existing technical standards and regulations in the building sector must be adapted to the requirements of climate change in order to promote the climate-adapted construction of buildings.
At the level of individual buildings, structural measures can help to reduce heating in the interior. These include shading elements, thermal insulation or climate-friendly architecture. In new buildings, greater attention should be paid to summer heat protection and ventilation options from the outset. In addition, greening measures in the building environment also have a positive effect on the indoor climate.
Indicators from the monitoring on the DAS: Green roofing of federal buildings, Specific energy consumption for space-heating by private households