The concepts of integrated water management that are well established today require strong integration and cooperation between all stakeholders including water managers, city planners, social scientists and economical experts. This clearly becomes even more important in the context of climate change and adaptive management. Ashley et al. (2008b) quoted Williams et al. (2007) that “without active stakeholder involvement, an adaptive management process is unlikely to be effective”. While traditional approaches in the urban drainage field include large engineering flood defence infrastructure, designed and implemented by engineers and funded through specific governance and institutional arrangements, climate change impacts and its associated high uncertainties require new ways of working between stakeholders. Schimeket al.(2008) point out that this requires a shift from a capital-focused approach to a portfolio approach that adopts the principles of asset management.
According to Ashley et al. (2008b), this requires a commitment to ongoing active learning and partnerships and collaborations via learning alliances. Active learning (also called social learning by Pahl-Wostlet al. 2008) leads to a shared understanding of the water system and the challenges facing this system. It can develop the capacity of various stakeholder groups to accept different interests and points of view on risk and performance of water systems. It also enables utilization of various types of response and if necessary at different times of implementation. Consequently it can lead to collective management of water resources in a sustainable way. The usefulness and importance of adaptive learning is shown by the fact that flood receptors (people, nature) have historically been able to adapt.
The history of human society indeed shows that communities have been aware of the need to live with flooding and have adapted through experience.
Ashleyet al.(2008b) point out that stakeholder participation and active learning processes require that professional and institutional stakeholders behave differently in regard to the public and community stakeholders by being more inclusive and willing to share knowledge at the appropriate levels. Many urban communities have to change their current held view that flood risks are unacceptable and that these risks have to be dealt with by governmental agencies. Also the role of the insurance industry has to be considered. In many European countries, citizens are routinely insured against flood risks. The same citizens, however, have to be aware that insurers are now re-appraising their position in areas where local flooding is becoming more common and where flood insurance may become too expensive in the future (Ashleyet al.2008b).
An example of stakeholder cooperation is the increasing demand for upstream stormwater storage and infiltration, which requires close cooperation with city planners. Given that it involves a decentralized approach of rainwater source control (see Section 10.2), which often involves locating storages on private land, the role of individual citizens is again shown to be of high importance (Stauferet al.2008).
This often introduces the challenge of dealing with a far greater number of participants, who are often supported by political representatives.
Following van Luijtelaaret al.(2008), 40% of the municipalities in The Netherlands say that public acceptance of water in the streets has clearly declined. This shows that it is necessary that adaptation strategies are combined with communication of adequate information on the controlled storage and discharge of water in the streets with the aim to prevent property damage. Through such stimulation of public awareness, individual property owners could also be convinced to contribute by restricting the impervious areas and by allowing rainwater infiltration on their own land. They also could be provided with relevant information about possible risks, thereby allowing the public to protect their own properties. Citizens and property owners could also help in keeping drainage inlets clear of leaves and debris during the flood season, to clear their own gutters, and to generally maintain the upstream property drainage systems.
Social scientists are able to quantify the risk awareness of the population and its willingness to take part in the change (e.g. German Klimanet project; Staufer et al. 2008). In cooperation with city planners, ecologists and social scientists, engineers can determine how the installation of additional stormwater storage and infiltration ponds can be integrated into the new urban form, thereby contributing to community wellbeing. They can indeed be seen in connection with planning of new recreational areas or other shared public spaces.
Given that these local scale measures will also affect more downstream water systems, cooperation needs to be organized between the local“municipality level”stakeholders (including city planners and potentially local property owners) and river basin or catchment authorities. As outlined above, the same applies to cooperation with insurers, spatial planners and other stakeholders. Adaptive management can also help to overcome conflicts which currently exist between these stakeholders, or between groups of stakeholders.
This can include conflicts between upstream and downstream water managers or between water managers and insurers.
These adaptation strategies have to go hand-in hand with “institutional adaptation” as explained by Crabbé and Robin (2006). These authors focused on the bureaucracies of Canada and the financial and physical responsibility that local municipalities will need to bear in adapting infrastructure to climate change. Attention was drawn on the institutional costs and the potential increases in both revenues and expenditures for local and regional governments when adapting to climate change. They also pointed out that there might be institutional barriers, such as a lack of skilled scientists and engineers and reliance on management-by-crisis rather than long-term management and planning. Crabbé and Robin (2006) proposed potential approaches that include easily understandable climate-change reporting, increased citizen participation and financial assistance from regional governments.
10.5 DISCUSSION
This chapter explained how we can cope with the climate trends towards more extreme short-duration rainfall extremes and related impacts in urban hydrology. Strong emphasis was put on the adaptive approach, which is commonly used in the ecological sphere, particularly in ecosystem rehabilitation and restoration planning, where uncertainties are very high and are scientifically acknowledged. Due to similarities with the high uncertainties in future climate projections, application of this essentially
ecologically focused approach to urban water and flood management would provide more timely achievement of objectives and more cost effective and feasible solutions. As shown throughout the chapter, adaptation involves the following three aspects.
– The need to change current water management strategies due to climatic evolutions. These include operational and infrastructural changes, but also changes in public awareness and expectation.
– The need to have flexible, adaptable, resilient and abandonable approaches. The approach in the past of using large infrastructure cannot be sustained as this will generally be unaffordable on the scale needed. It will also“lock in”the use of the large infrastructure for many decades and perhaps even centuries. The performance of any solution to the flood risk problem will degrade over time; hence, there is a need to respond over time as the external climate drivers evolve and as assets deteriorate with time (Ashleyet al.2008b).
– The ability to try different approaches or solutions, abandoning those that are found to be ineffective or inefficient.
Given that climate change occurs gradually (most of the projections summarized in the Chapters 8 and 9 were for the next 50 to 100 years), there is no need to invest heavily today in upgrading all infrastructure as soon as possible. Instead it is recommended that the potential consequences of current climate projections are assessed and that this knowledge is incorporated into current and future maintenance plans.
Points of interest for adaptation are favourably located at the head of the urban drainage system. This may involve source control through disconnection of impermeable surfaces, increased retention and infiltration, as well as upstream pollution control. There will be a need for more natural urban drainage approaches and installation of “green”stormwater infrastructure, all of which requires a change in design philosophy.
There will be an increasing need to incorporate roads and parks into the active urban drainage system.
This may be a new situation within parts of Europe, but as Grum et al.(2006) and Parkinson (2003) pointed out that this is common practice in tropical regions. It also fast becoming mainstream practice in Australia (Beecham, 2012). In addition, the design and management of urban drainage systems needs to change. There is a current trend of reducing the role of experts. There needs to be more focus on controlling local damage, for which specific knowledge and expertise is required which is in contrast to the general perception.
Important to note in this respect is that, in contrast to many water management sectors, adaptation of urban drainage systems is mainly undertaken at the municipal level. Municipalities and authorities responsible for local drainage as well as wastewater collection and treatment are also responsible for addressing climate change effects in their master plans for drainage, sanitation, development and area planning. These authorities have the means to install alternative decentralized stormwater retention, local infiltration and controlled surface flood ways and to regulate these measures through planning and building laws. Through these means, municipalities can prevent undesirable building developments.
Through long-term area planning, a more controlled approach to planning can be considered. Hence, climate adaptation measures can also help achieve other municipal sustainability goals and should not be considered only as stand-alone actions to address climate change (Richardson, 2010).
The majority of the book is devoted to understanding the complex hydrological cycle with focus on extreme precipitation and notably how to predict the frequency and size of future extreme precipitation.
However, this chapter clearly shows that there are other equally important drivers within the context of design and performance evaluation of urban drainage infrastructure, namely intense city development and change in people’s perceptions and preferences over time. The last 160 years there has been one dominating concept of urban drainage: an underground piped network where the water is moved by means of gravity. The service levels have been set by engineering communities without much public debate.
This concept is now being challenged by both deteriorating infrastructure in the developed world and difficulties in generating the capital costs needed for establishing the infrastructure in the developing world. In combination with a higher demand for quick return of investment and higher awareness of future changes there is a recognised need to rethink the concepts of urban drainage. Climate change impacts on precipitation clearly show that a business-as-usual approach is not feasible in many regions of the world. The issues raised in the present chapter point out, that it is in many situations necessary to re-evaluate the entire concept of urban drainage rather than“just”upgrading the technical solutions we have implemented over the last 150 years. It is necessary to establish and maintain hygienic barriers and to build cities that interact with water in a healthy, environmentally friendly, and cost-efficient way. This may include the use of sewer systems, but perhaps other solutions should be investigated as well.