How WSUD supports climate resilience
Water sensitivity in urban environments seeks to transform cities and communities in a way that can help them to live in harmony with natural water environments while supporting the economic and social functions of urban areas. Water sensitive urban design (WSUD) provides methods of managing the water cycle in the urban landscape and creating opportunities for the integration of nature, which are able to both mitigate and adapt to the impacts of climate change at local and regional scales.
WSUD principles and practices include many climate change mitigation and adaptation actions such as water conservation, creating urban forests and resilient communities, providing flood protection and appropriate infrastructure for future conditions, and disaster management.
Water conservation and efficiency
WSUD seeks to reduce water demands within urban areas by mimicking natural hydrological processes and creating landscapes that are reflective of local conditions. Plants that are adapted to local soil conditions and temperatures require less water than those adapted to wetter climates and conditions.
By considering the total water cycle, WSUD aims to capture, store, treat, and reuse water in a manner that aligns with natural systems and optimises use and reuse. This principle emphasises the interconnectedness of water sources, such as rainfall, groundwater, and surface water. It encourages the use of water as a valuable resource rather than a waste product through measures like rainwater and stormwater harvesting, wastewater treatment and reuse, water efficient landscaping and minimising water loss through evaporation and runoff.
Resilient communities
WSUD promotes development of integrated strategies for ecological, economic, social, and cultural sustainability. It emphasises the connections between water, vegetation and the built environment, aiming to create sustainable and resilient communities, by providing a pathway to integrate built and natural form and character.
WSUD approaches provide urban areas with an enhanced capacity to adapt to and cope with intense rainfall events, through creating distributed storages throughout the catchment and using natural systems to manage rainfall and runoff. This promotes resilience at the local level, as well as at a catchment scale.
Passive irrigation interventions and permeable surfaces contribute significantly to urban cooling through soil moisture, sustaining healthy vegetation and resilient urban landscapes, while reducing run-off into the stormwater systems.
WSUD approaches also seek to create sustainable landscapes and reduce long term maintenance costs. Incorporating tree-pits into streetscapes helps minimise both capital and operational costs associated with stormwater management infrastructure. In addition, shade from trees can protect roadways, therefore reducing the amount of asphalt re-seals needed over a 30-year period, thereby saving money on road maintenance (McPherson and Muchnick, 2005).
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Flood protection
In natural environments, rainwater from small rainfall events mostly evaporates, is absorbed by plants or soaks into the ground. Urbanisation dramatically changes these processes with impervious surfaces that restrict water infiltration and increase stormwater runoff. High intensity rainfall events are increasingly leading to flash flooding, while sustained, longer duration rainfall can lead to major catchment and city flooding.
WSUD provides flood protection through various mitigation measures, by providing stormwater detention and/or retention and reducing storm event flow volumes and rates. WSUD also promotes the safe, overland flow of stormwater and conveying larger events in natural systems. These natural systems are often more resilient to flood flows than engineered systems, particularly in extreme rainfall conditions.
Permeable paving and other WSUD practices can manage frequent rainfall events and mitigate local flood risks. Permeable pavement is an effective tool for hydrologic mitigation of storms from “every day events” up to the 10-year, 24-h average recurrence interval or 10% AEP (Fassman and Blackbourn, 2010).
Disaster management
WSUD approaches recognise the importance of preparing for and managing the impacts of climate change, such as floods, bushfires and heatwaves. This includes increasing community awareness and preparedness for disasters.
Recent events have raised the awareness of many communities to bushfire and flood risks, and there is increasing awareness of heatwaves and their impact on the community. Linking WSUD solutions to the mitigation and adaptation of these risks and events will continue to increase community support for these solutions.
References
DWER, 2020, Climate change risk management guide: Practical guidance for the Western Australian public sector to assess and manage climate change risks.
DWER, 2020, Western Australian Climate Policy: A plan to position Western Australia for a prosperous and resilient low-carbon future.
Fassman, E, and Blackbourn, S, 2010, Urban runoff mitigation by a permeable pavement system over impermeable soils. Journal of Hydrologic Engineering, vol. 15, no. 6: 475-485.
IPCC, 2013, Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change
McPherson and Muchnick, 2005, Effects of street tree shade on asphalt and concrete. Journal of Arboriculture, 31(6): 303-310.
UN-Water, 2010, Climate change adaptation: The pivotal Role of Water.