Study into the climate-resilience of Haarlem

Results

The study shows that in the coming decades, climate change will increasingly impact the residents of Haarlem as well as visitors. The effects of heat, heavy rainfall and dry periods will bring the largest risks to Haarlem. The number of hot days will increase, which in a compact city such as Haarlem, with its many paved and brick surfaces, will cause heat stress. Heat stress is responsible for health problems among vulnerable groups of people, such as the elderly; it brings an increased risk of power grid failure and of legionella forming in the drinking water network. Heavy rainstorms produce pluvial flooding in the street, causing water damage in homes and shops, and traffic congestion. Long-term drought can increase the risk of damage to wooden foundations (pile rot). The risk of damage caused by climate change is heavily dependent on one’s location and situation. The neighbourhoods that will be most vulnerable to damage ensuing from climate change will be those with a predominance of paving, little green vegetation, many elderly people living independently, and pre-war homes.

The natural system plays an important role in the study. The consequences of climate change for Haarlem are, after all, determined to a significant degree by the spatial structure and the design of the city, and the opportunities and limitations of the natural system made up of soil, substrate, groundwater, surface water, Nature, and green vegetation. An analysis of the financial consequences of the damage (CliCo analysis) revealed the following:

I: Flood risk management: If the dykes are not reinforced, the costs of damage/loss caused by flooding from the primary flood barrier for Haarlem will increase in the period 2015-2050 by a maximum of 0.4 million euros. These costs are relatively low because the risk of damage is relatively limited. Haarlem lies largely above sea level. The damage will be caused by the flooding of homes, infrastructure, recreation amenities, greenhouse horticulture, and the urban area.

II. Pluvial flooding: The more frequent occurrence of extreme rainstorms is expected to result in an additional 0.6 to 5.9 million euros of damage-related costs due to pluvial flooding in Haarlem in the period 2015-2050. It is likely that these damage-related costs have been underestimated in this study: the national road database has a low-level of geographic accuracy, which means that any pluvial flooding cannot be linked to a specific road. The damage cannot be established as a result. No detailed alternative was available to determine the damage.

III. Drought: This analysis examined the effect of climate change on the damage-related costs due to drought for building foundations, urban vegetation, and garden maintenance. The damage is estimated to come to between 280 and 660 million euros based on 20,000 damage-sensitive homes. The maximum damage calculated is considered to be an absolute upper limit. It is improbable that the upper limit will be achieved completely: groundwater levels in Haarlem are actively regulated and preventative action is also taken locally. Persistent drought will also cause damage to urban green vegetation; these costs are estimated at approximately 2 to 8 million euros. The expected increase in precipitation deficit by 2050 will result in increased management costs. In addition to the management costs for urban vegetation, the costs of water consumption for private gardens will also increase as precipitation deficits increase. Measures are taken to prevent (excessive) damage during long droughts.

IV. Heat: The CliCo analysis takes account of the connection between the increase in temperatures up to 2050 and the related number of deaths and hospital admissions. Hot summers with greater temperature extremes will, in certain scenarios, lead to an increase in mortality and hospital admissions during the summer months of July and August by 2050. Heat can also cause damage to asphalted roads used by heavy traffic. The largest damage will be caused by the loss in labour productivity. Up to 2050, this cost is estimated to be between 19 and 48 million euros.

V. Severe weather, thunderstorms and hail. The consequences of extreme weather conditions are difficult to estimate. Storms in the Netherlands are responsible for average losses of € 50 million a year. It is not clear what proportion of that amount in damage occurs in Haarlem. If we assume that storm damage in the Netherlands is evenly distributed, then future losses due to storms in Haarlem will average around 450,000 euros a year. Hail damage will produce a loss of 320,000 euros a year.

In addition to the analysis of the potential costs of damage due to climate change, a Natural Alliance Atlas has been developed. This atlas documents the analysis of the natural system. The atlas comprises approx. 25 source maps with detailed aspects, such as elevation, seepage, and main green structure. The source maps are integrated into four theme maps (soil, groundwater, surface water, and Nature/greenery). From the theme maps and remaining source maps, three primary maps have been distilled that can form a foundation for the adaptation vision: a landscape map, a map with climate effects, and a map with vulnerable groups of people and functions.

The municipality of Haarlem is already active on various fronts with measures geared to climate change. The subsequent approach should be focused on extra accumulation of knowledge aimed at the development of a strategy on regional and local scales. On a local scale this could be a district profile for climate adaptation based on the natural, urban and social features of a district. The implementation, such as securing climate measures in the spatial planning vision for public spaces, requires an integral approach. Another recommendation is to start a district pilot project with residents and companies that is focused on improving the living environment in general terms.

Contact person

Ron de Kooker
Municipality of Haarlem
rkooker@haarlem.nl