How we're keeping Danish cities above water

Coastal areas are exposed to various water-related hazards, including storm surges, flash floods and tsunamis. Nevertheless, these areas are highly attractive to human settlement, making them some of the most densely populated regions in the world. These factors contribute to the high levels of flood risk along urban coasts. Examples of more recent coastal floods during hurricanes Sandy and Irma, which resulted in vast inundations and tremendous damage. Rapid rates of urbanization are projected to continue in the future; combined with the impact of climate change, significant increases in flood risks in urban coastal communities are expected.

One way forward is to make informed decisions about present-day flood risk and the future impact of climate change. Here, big data and consistent analysis by computer model form the basis for preparing Danish cities for the future.

In 2011, the Danish government decided that all its cities had to prepare for the future by preparing maps of today’s flood risk together with the risk under an altered climate in the year 2100. In order to facilitate this, the government ordered a high-resolution survey, where the terrain in the whole of Denmark (43,000 sq km) was surveyed and turned into a digital atlas. The atlas contains a digital terrain model specifying the locations of houses, watersheds, etc.

In addition to the digital atlas, the Danish Water and Wastewater Association published guidelines on how to make consistent analyses concerning climate changes and the impact on flood risk.

Based on the digital atlas of Denmark, 99% of all Danish municipalities have made flood-risk maps showing the risk today and for the climate in the year 2100, covering both pluvial and coastal flooding.

In addition to this long-term planning, the use of flood-warning systems provides a means to effectively prepare for and respond to current flood events allowing optimal use of existing infrastructure and reduction of flood impacts. The combination of approaches that ensure sufficient time to mitigate flooding impacts can be used to complement structural measures, such as reservoirs and levees.

Based on freely available data, flood-warning systems are under development in Denmark. The aim is to detect and forecast potential flood events in order to provide alerts in advance, enabling people to undertake appropriate measures or responses to minimise the impact. This will provide time for them to establish temporary dykes, blocking the flood and protecting lives and property.

The data, consisting of the digital atlas, flood-risk maps and real-time information systems, form a basis for a cost-efficient minimization of current and future flood damages, and provides a safe and consistent basis for a prosperous development of the Danish cities.

The data, methods and principles applied in Denmark are all generic and can be transferred to any city or country in the world.

Data Driven Cities: 20 Stories of Innovation is out now. Read the full paper here