For many years there has been a tendency that a large amount of precipitation has fallen in a short time. Næstved and Greve are examples of two Danish towns which have experienced heavy precipitation activity. The heavy precipitation has given problems, such as water in the basements of private homes and public institutions, but the road network has also been flooded, which has made travelling difficult. In England, the motorways M5, M25 and M50 have been closed due to flooding, caused by extreme precipitation in the summer of 2007. In the worst case, M25 was closed on a warm summer day, where drivers could neither come backward nor forward. The British emergency services had to fly drinking water supplies to drivers in distress by helicopter. The last drivers could leave the M25 after being caught for twelve hours. The operation and help cost large amounts of money.
The climatic changes which are predicted by the Intergovernmental Panel on Climate Change (IPCC) point towards more precipitation seen on average throughout the year as well as stronger and more intense shower activity in summer. This means that the drainage systems of the road network must be prepared to drain larger amounts of water and in extreme cases in relatively short periods of time. The existing drainage systems are designed and constructed on the basis of previous precipitation events (statistics). Similarly, more net precipitation leads to larger water stream flows, possibly causing problems with present culverts that are designed based on outdated statistics of high flow events. It is obvious that an upgrade must take place soon. But if this is done from “one end to the other” it becomes very comprehensive and expensive and presumably also unnecessary. In many places, additional capacity already exists.
The project is of type application research and refers to two topics: 1) Climate Impact on Road Infrastructure and 2) Road Infrastructure Capacity for Climate Change.
The purpose of this project is to point towards a method of upgrading the drainage system in an optimum way, in other words to find the most exposed places, called “blue spots” (part 1) and deal with them first. When the exposed places have been identified it will be necessary to evaluate (part 2) how the upgrade is carried out in the best manner. In many cases only individual elements in the system are a weak link. How can they be identified and repaired? Much money can be saved by tailor-made solutions.
According to the questionnaire, maintenance rather than bad design is thought to be the reason for most flooding related problems. Supposedly, this means that the previous design guidelines regarding flooding have at least not led to under-dimensioned systems, which is encouraging and promising. They may of course be over-dimensioned though, which in most situations sounds bad, but may prove to be a good thing since this would mean that they are in a sense already adapted to climate change (i.e. there is already room for more water in the pipes).
Documentation of most information of interest (as the design of the road or drainage system) is more or less absent in many countries. Proper investigation and documentation of previous flooding events is invaluable, but mostly lacking. These are problems that should be addressed.
As a result of the uncertainties regarding the development of the future climate, road agencies have chosen different approaches to climate adaptation in different countries. Despite the uncertainties, most countries studied have presented recommendations associated with the design of new roads that are intended to adapt the roads to future climate. How to deal with the already existing road network is more unclear. It seems that for example drainage systems are always upgraded, never downgraded, despite predictions of drier conditions in some regions.
It is likely that climate researchers will be unable to provide society with definite and certain numbers of e.g. percent change of precipitation in a given region for a given decade or whatever the time scale might be. It is also likely that as models and theories develop, new and perhaps surprising results will emerge; particularly on the small regional, or even local scale. It is therefore necessary that road agencies remain as flexible as possible when preparing guidelines, follow the climate science development, and adjust design or maintenance guidelines accordingly.
Given the mentioned difficulties, it is important to give thought on how to proceed. The SWAMP project has presented a systematic approach to preparing the road network for floods. The method covers the entire chain of procedures, starting with the identification of weak spots (in this work referred to as blue spots) and ending with guidelines on how to reduce the risk for, or impact of, flooding at the local site. Hence, we suggest taking action at the spots that are identified as problematic, despite the magnitude of climate change. Some of the adaptation components are better monitoring at blue spots, combined with better information to road users.