Climate-proof retrofitting of urban areas for the same cost

Due to climate change the frequency of extreme precipitation increases. To reduce the risk of damage by flooding, municipalities will need to retrofit urban areas in a climate-resilient way. To justify this investment, they need insight in possibilities and costs of climate-resilient urban street designs. This chapter focused on how to retrofit characteristic (Dutch) typologies of urban residential areas. For ten cases alternative street layouts were designed with a determination of the life cycle costs and benefits. All designs are resilient to extreme rain events. The results show that most flat urban typologies can easily be retrofitted in a climate-resilient way without additional costs compared to the standard way of retrofitting. Climate proofing sloping areas are highly dependent on the situation downstream. When there is no space downstream to divert the water into waterways or parks, costs to provide storage easily rise above traditional levels for retrofitting. In addition to reducing flood risk, for each case one variant includes resilience to extreme heat events making use of green. The life cycle costs and benefits of the green variants showed that especially green designs in high-density urban areas result in a better value for money.

Our climate is changing. The world is gradually warming up, and more extreme 41 weather events, from rainfall to drought and heat, are expected. The impact on the 42 world as we know it will be tremendous. Sea level rise can have devastating effects 43 on our coastal habitats, where over half a billion urban residents live and population 44 growth is expected to be high (Merkens et al. 2016; Neumann et al. 2015) affecting 45 even more people in the future. Extremes of drought, resulting in desertification or 46 crop loss, and flooding will become more common, causing displacement and 47 conflict. Heat and heat waves will impact human health, biodiversity, and ecosys48 tems. No matter what you are passionate about, something you value will be affected 49 by climate change. 50 Our urban areas will be affected by climate change as well. Today, 54% of the 51 world’s population lives in urban areas, a proportion that is expected to increase to 52 66% by 2050 (UN 2014). “Managing urban areas has become one of the most 53 important development challenges of the 21st century,” according to John Wilmoth, 54 Director of UN DESA’s Population Division. Urban areas will mainly be affected in 55 three ways by climate change: (i) change in rainfall patterns, (ii) increase in (occur56 rence of) extreme heat, and (iii) sea level rise leading to inundations or problems 57 with water discharge. This chapter will not discuss the issue and problems associated 58 with sea level rise nor will it analyze comprehensively the effects of heat waves. This 59 chapter focusses on the change in rainfall patterns and its impact on urban areas. Due 60 to climate change, the force and frequency of extreme rainfall events are increasing 61 in large parts of Europe (and other parts of the world), and more water will fall in 62 shorter spells of time. People have been building sewer systems for wastewater and 63 stormwater in cities for more than centuries, and there have always been extreme 64 rainfall events that the drainage system could not cope with, causing flooding. So, 65 nothing new? The force and occurrence of extreme rainfall events are increasing so 66 fast that adaptation to climate change is required. In this case adaptation means 67 higher water storage capacity of excess water on the surface and water conservation 68 to cover dry periods and to reduce excessive groundwater level changes. The urban 69 design focus is shifting from direct discharge to storing and retaining water. 2 L. Kleerekoper et al. 70 Even today, more and more cities are experiencing extreme weather situations 71 such as cloudbursts and the associated damage and repairs. Many cities around the 72 world have started investigating the local impact of climate change and particularly 73 of the hazards of extreme weather. Nevertheless, there seem to be structural obstacles 74 to integrating climate change solutions in all refurbishment and maintenance oper75 ations and to moving from “knowing” to “doing.” Changing the infrastructure 76 requires a new perspective on urban planning. One of the problems is the lack of a 77 standard definition of what climate resilience actually is – at least in the Netherlands 78 this is an obstacle. 79 It is a political decision to tell if and how often disruptive effects of extreme 80 rainfall are considered acceptable. The essence is that urban planning must take heed 81 of the increasing frequency of extreme weather (cloudbursts, drought, and heat 82 waves) and its consequences. Urban design must adapt to the changes in extreme 83 weather events. In this chapter climate-resilient urban design means taking initiatives 84 to encourage soft surfacing, greening, and creating space for water and buffers to 85 store it for dry spells. 86 In the Netherlands, insight in consequences of climate change has resulted in a 87 new policy aiming at climate proofing all built-up areas. Every construction, recon88 struction, or refurbishment of urban areas should be done in a climate-resilient way 89 from the year 2020 onward (Deltaprogramma 2014). Assuming a reconstruction of 90 the roads in urban areas at least once in 30 years, this should result in a climate-proof 91 urban environment by 2050. 92 In order to investigate how this climate proofing should and could be done in 93 residential streets, a research has been carried out in 2015 and 2016. This research 94 aimed at showing the possibilities and showing the cost of the different options, as 95 this often is of main importance. 96 Institutions in the field, such as municipalities and consultancies, express the 97 need to move forward and tackle the structural obstacles to integrating climate 98 change solutions in all refurbishment and maintenance operations. The profes99 sionals indicate a great need for inspiring practical examples with reliable tech100 nical underpinnings and an estimate of the cost and benefits. This chapter 101 therefore aims to inform designers, technicians, and governors alike. This chapter 102 provides examples of illustrative designs and financial substantiation. The AU3 103 conducted research is not only meant for professionals, but thanks to these same 104 professionals it was made possible. The Dutch municipalities of Almere, Almelo, AU4 105 Amsterdam, Arnhem, Beverwijk, Deventer, Eindhoven, Enschede, Groningen, 106 Haaksbergen, Hoogeveen, and Houten and the (regional) water authorities 107 Waternet, Waterschap Drents Overijsselse Delta, RWS, the Dutch Ministry of 108 Infrastructure and Environment, STOWA, SBRCurnet, and Tauw supported the 109 research by providing the case studies or values comments on methodology and 110 research outcomes. 111 Ideally, every case of urban retrofitting or maintenance should consider options 112 for climate resilience when refurbishing streets and when renovating or building new 113 residential areas and business districts. This chapter presents examples and offers Climate-Proof Retrofitting of Urban Areas for the Same Cost 3 114 knowledge and practical information to inspire and convince urban planners to take 115 measures