Editorial

Storms soaked southern parts of Manitoba (in Central Canada) last Wednesday, leaving one small town flooded up to its knees. St-Pierre-Jolys, a community of about a thousand in the south-eastern part of the province, was hit with at least 75 mm of rain in one hour, according to Environment Canada. In the main part of town, water pooled up to one meter deep, forcing some to stay up late helping as the aging infrastructure struggled to handle the water. Mayor Mona Fallis said she was in a meeting when the skies opened up. “We knew it was raining, and when we came out, all of the streets were flooded at least up to the curb,” said Fallis. Though summer storms are common in the area, Fallis said this one was exceptional: “Never in my 50 plus years living in this community have I ever seen the water come up so high so quickly.” Brandon, Manitoba, a city in the southwest part of the province, was also hit with about 60 mm of rain from the storm system that brought 100-kilometre-per-hour gusts and coin-sized hail. Summer storms in the area were never the main source of flooding. Nearby large prairie rivers, Red and Assiniboine, were creating a huge flood damage in 1886, 1950, 1997, 2011, 2013 as a consequence of typical snowmelt driven spring flooding. The residents of these communities are learning about the new reality and ‘new type of flooding’. The rest of Canada seems to be exposed to a very similar changing conditions and pattern of flooding. The Insurance Bureau of Canada and the Institute for Catastrophic Loss Reduction in unpublished analyses (2014) are showing that direct insurance payments due to urban flooding have reached $2 billion annually. Canadian and US engineering practice for more than 100 years considers design storms using: (a) design return period; (b) storm duration; (c) intensity–duration–frequency (IDF) relations (representing a summary of historical rainfall data); (d) temporal distribution (design hyetograph); (e) areal reduction factor, and (f) antecedent moisture conditions. Concerns about climate change and the need to adapt prompted many municipalities in Canada to revisit the design storm event issue, particularly in connection with drainage design. It appears that this analysis has mostly focused on a single property of design storms – IDF relations and projected increases in rainfall intensities. However, the design practice would significantly benefit from adoption of a comprehensive approach considering all design storm event characteristics and their sensitivity to climate change and inherent uncertainties in the existing IDF relations as well as hydraulic design of sewer networks. Traditional urban flood management options based on the fast removal of excess water using underground pipes and sewers has been criticized in the light of many costly urban food disasters. The evolution of urban flood management moved from structural solutions to a combination of structural and non-structural measures or integrated flood management that has been heavily promoted by the World Meteorological Organization. Current practice is continuing along the same line by offering as an alternative to conventional drainage to mimic natural drainage. These approaches are given a new name and are referred to as sustainable drainage systems (SUDS). These may take form of green roofs, or natural water storage features like ponds. There are some engineered components of SUDS such as porous paving. While the components can differ greatly, all SUDS use one or more of the following: encourage infiltration; reduce peak flow rates of runoff (attenuation); transfer runoff in a controlled manner to other locations; and/or capture water directly on site for controlled discharge later (storage). One possible extreme could be complete switch from underground to management of urban runoff on the surface. Under this approach, runoff from roofs, roads and paving could be disconnected from underground drainage. Instead, the new developments would be designed to direct the flow on the surface. Under normal rainfall conditions, the water would either infiltrate into the ground, or be collected for use. When there is heavy rainfall, the excess water would be directed to low value areas (with warning) and away from houses and important infrastructure. Green spaces and roads could provide temporary storage for the floodwater. Simple aspects of development design, such as curb heights and the amount of vegetation cover, can have a dramatic impact on the way water flows though the urban environment. Canada does not properly manage its flood risk. Urban flood management aims to reduce harmful impacts of flooding to people, the environment and the economy of a flood-prone area. The most general definition of flood risk combines consideration of the flood hazard and its consequences. In many cases those consequences are not all or, at least, not systematically quantified so that objective risk can be assessed. Therefore a full appreciation of flood risk remains unknown or is driven by individual perception of consequences (subjective risk). For any flood prone urban area where significant losses can be expected during extreme floods a primary task should be to quantify flood risk and provide decision makers and the public with the tools to assess and compare the benefits of various flood risk reduction options. Under a changing climate, flood risk management should be considered as a framework for identifying, assessing and prioritizing climate-related flood risks and developing appropriate adaptation responses. Integrated urban flood risk management involves complex interactions within and between the natural environment, human population (actions, reactions, and perceptions), and built environment (type and location). In addressing the question of “what kind of problem a city is,” Jane Jacobs (1961) wrote: “Cities happen to be problems in organized complexity . . . present(ing) situations in which a half-dozen or even several dozen quantities are all varying simultaneously and in subtly interconnected ways. The variables are many, but they are not chaotic, they are interrelated into an organic whole”. A different thinking is required to address the organized complexity of the urban flood risk management. I am strongly suggesting adaptation of a global systems perspective. The idea that nothing exists in isolation − but only as part of a system − has long been present in the consideration of urban settlements. Urban governance, including urban flood risk management, in the face of rapid climate destabilization is in need of a new (old) approach so that sustainability becomes the norm, not the occasional success story. A systems approach may be the answer. The challenge is to transition organized urban complexity built on an industrial model and designed for automobiles, sprawl, and economic growth into coherent, civil, and durable places. A systems perspective to urban governance including flood risk management offers a clear view of change, and potentially provides for better management of the complex cause and effect relationships between social and ecological phenomena. systems analysis can help urban governments organize flood related information in order to distinguish the important signals from the noise and improve decision-making across sectors, departments, and agencies; the data necessary to understand resource flows and the larger urban context can be deployed to educate a public to understand the relationships between its behaviour and environmental and economic consequences of urban flooding; systems analysis can help to improve planning and flood forecasting: the tools of systems analysis can help to improve the quality of urban flood risk decision-making; systems analysis can improve flood emergency behaviour by using systems thinking to build organizational community around common visions; and systems thinking can lead to greater realism and precautionary urban flood risk policies for the simple reason that most systems are nonlinear and therefore inherently unpredictable. Urban flooding, being at the intersection of human action and biophysical realities requires smarter and more adaptable actors, capable of learning and having foresight.

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