by David Higgitt and Gary Brierley
he summer monsoon season of 2010 wrought havoc across many parts of Asia. Unprecedented floods in Pakistan unleashed a humanitarian disaster. China experienced widespread floods in the South and rain-induced slope instability in the North-west. Severe floods occurred in the central part of the Irrawaddy basin in Myanmar, induced by strong incursions of moist air from the Bay of Bengal. Even Singapore suffered from three incidents in June and July that caused significant damage to property. Images of Orchard Road underwater caused local embarrassment, reigniting debate about the role and responsibility of authorities to ensure flood protection. The aftermath of floods tends to focus attention upon the performance of engineered systems, typically invoking approaches such as widening drains or raising road levels. However, this is not the only solution to flood hazard, and emerging approaches to flood risk minimization has framed this issue in a much broader context. Such thinking builds upon continuing battle between flood hazard and technical solutions. Integrated approaches to river management increasingly frame these issues in relation to the concept of river repair. It is timely to consider new approaches to the management of flood hazards in Asian cities.
The recent history of flood management in Asian cities has largely been approached as a technical exercise. Floods are regarded as a threat requiring control through infrastructure and management by institutions. Such a reaction differs markedly from traditional land use practices that adapted to monsoon flood regimes across Asia. Settlement patterns and cultural practices evolved to accommodate the annual flood cycle. However, flood management is a moving target. Rapid urbanization has imposed increasingly difficult flood management challenges. Impermeable surfaces generate rapid runoff and flash flooding. Flood protection works have encouraged the expansion of cities into flood-prone areas. Land use zoning has often been ineffective in preventing settlement in these locations, placing property and communities at greater risk. Approaches to flood management in expanding urban areas have reallocated risk as channel and floodplain modification has altered flood regimes, and demands for flood protection in some locations have redistributed risks to other areas downstream. To date, this question of how structural intervention at one location redistributes risks and results in some groups being more vulnerable to flooding than others has received limited attention in Asian cities. Impacts of climate change will likely exacerbate these concerns through enhanced extremes of rainfall intensity. Viewed in this way, the prospect of addressing flood hazard solely through so called “command and control” engineering solutions looks problematic. From an earth science perspective, a longer term understanding of river flow dynamics is necessary. Outside China, few Asian countries have river discharge records going back more than a century. But the record of past floods can also be uncovered from the sediments preserved in depositional environments such as floodplains and wetlands. Interpreting the recent geological record for information about flood hazard over millennial scales would enhance our assessment of contemporary risk, providing clearer guidance upon the natural range of variability of these systems, and the recurrence intervals of large flood events.
Against this context of increasing concern about flood hazard across several Asian cities, there are signs of an emerging international movement towards integrated river basin management – a movement which recognizes that restoring and sustaining functional river ecosystems with high biodiversity is one of the greatest challenges facing society. In several Western countries, most notably in USA and Australia, societal demands for river rehabilitation have resulted in large-scale initiatives to recover or restore damaged aquatic ecosystems. In the European Union, the Water Framework Directive provides a blueprint for maintaining water quality, protecting high value ecosystems and recognizing the ecosystem services provided by rivers. These initiatives demand a new approach to river basin management, where interdisciplinary activity across the water-related earth sciences, particularly engineers, hydrologists, geomorphologists and ecologists, is tied more effectively to social science perspectives, and these understandings are appropriately framed within an institutional context.
Emerging approaches to river rehabilitation increasingly emphasize the importance of social inclusion in the management of river systems. These applications strive to protect infrastructure and associated human needs/demands while looking after ecosystem services and enhancing/protecting environmental values. Such applications are especially important in urban settings. Catchment-framed measures increasingly strive to tackle problems at source, through programmes such as retention basins, additional use of wetlands, ‘space for water’, or water sensitive urban design (low impact design). In many instances, these applications simply re-engineer notional solutions. More sustainable long-term outcomes are likely to be achieved by framing these issues in a broader social and institutional context, working with local communities. In this context, management of urban streams plays a pivotal role in raising societal awareness of environmental values and sustainability principles. Relatively simple, low cost measures can be applied to improve ecological conditions. For example, emplacement of resistance elements can improve the physical diversity of a channel; the heterogeneity of messy channels provides a far wider range of habitat than tidy streams. In this light, the role of riparian vegetation and wood is especially important. Ultimately, the health of urban streams reflects societal attitudes to our watercourses. Managing people is the key to effective management of river health. Our attitude to environmental values is integral to the generation and sustainability of resilient communities.
An integrated approach to flood hazard management in Asian cities is the subject of a new research project being funded through the NUS Global Asia Institute (GAI). The mission of GAI is to provide in-depth insights to shape agendas for Asia in the twenty-first century. It focuses on integrative studies cutting across boundaries of disciplinary knowledge to focus on issues critical to Asia. The research project will examine the potential for integrated approaches to flood management through selected case studies of Asian cities. For example, the Ping River flows through the northern Thai city of Chiang Mai. Flooding is a frequent problem and appears to relate to urban encroachment onto the floodplain in recent years. Analysis of river flow records suggests a strong influence of El Nino events and typhoon disturbances on rainfall totals. Jakarta has a significant flood problem compounded by rapid rates of subsidence which increase risk from high tides as well as from storm events from the Ciliwung River. The river is an extreme example of floodplain encroachment with many squatter settlements building houses on the banks of the river.
In the aftermath of the 2010 floods across Asia, it may seem that the imperative of structural intervention to improve drainage and a broader concern with the ecological health of the river are working at cross purposes. Asia, some might contend, cannot afford to be sentimental about the aquatic ecology when dealing with the reality of flood hazard. The goals of a command and control strategy are typically focused on a single issue (flood control) approached primarily as a technical problem. This is manifested in the way that rivers in many Asian cities have been conceptualised as conduits whose function is to remove waste products (excess water, sediment and associated contaminants). Often these conduits are hydraulically smooth artificial channels which are separated visually and physically from surrounding human activities. This situation was typical in Singapore where straightened monsoon drains were constructed as part of new town development to serve flood control purposes. With changing perceptions of water as both a valuable resource (and the need to retain as much as possible for potable supply) and as a landscape feature integral to the image of a green (eco) city, the traditional approach to channel construction is being challenged. There are signs that the river repair paradigm can be established in the region. In Singapore, the ABC Waters Programme developed by the Public Utilities Board contains many elements of the philosophy of river repair. It repositions the focus from traditional functions of command-and-control engineering towards a more ecosystem-based approach. Perhaps pragmatically, much of the emphasis of the programme has focussed on aesthetics – the idea of making the engineered river landscape more attractive and, by doing so, more amenable to recreational and community use. The Asian River Restoration Network (ARRN) was established as a non-governmental organisation in 2006 to promote the exchange of knowledge and technology, particularly in relation to the Asian monsoon. National networks have been established in China, Korea and Japan, with the latter country providing secretariat support for the Asian network. ARRN argues for the necessity of countries in the Asian monsoon region to develop and share strategies for river restoration given the dense populations, regime of frequent flooding and abundant rice paddy.
River repair requires a whole of system approach which identifies the needs of water users and meets ecological objectives. Faced with significant management problems, particularly the threat of flooding, a more holistic approach to managing rivers may find little credence among river managers and politicians. The development of the river restoration movement in the United States was largely driven by communities. Some impetus has come from new approaches in earth science as traditional reductionist approaches to site-specific problems are seen to be inadequate to deal with the complexity of ecological conditions. But equally strong demand comes from voters and influential leaders in local communities who desire an approach to river management which is more sympathetic to the maintenance of ecologically productive rivers and which aims to improve on past degradation. Whether such western ideals are ready to be applied to Asian cities is another matter. The perceived importance or river health among local communities may be rather different to the views expressed in western countries. The GAI project will therefore seek to establish the range of ‘visions’ for managing rivers and flood hazard in Asian cities.
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