Uncovering the Hidden Impacts of Rainfall Reflected off Hot Urban Surfaces on Water, Land, and Marine Environments

Christine Lauchlan Arrowsmith 's recent LinkedIn post and comment (https://www.dhirubhai.net/posts/christine-lauchlan-arrowsmith-05691a28_why-the-water-at-the-beach-is-warmer-than-activity-7054225301807001600-6KWf) is a topic worth exploring in more detail.

Following the release of the ABC's Tom Saunders' article on ocean conditions reaching record highs, Christine pointed out in a LinkedIn response that the impacts extend beyond the beach and also affect our coastal and marine ecosystems.

It's not just the beach - what about the impacts on our coastal and marine ecosystems....

A lesser-known reason for the warmer-than-usual coastal beach environments and particularly water temperature during this time of year is due to the reflection of rainfall off hot surfaces. In Australia, most populations reside close to the coastline and within impervious urban landscapes. These landscapes have been engineered with dense graded asphalts, concrete, metals, and plastics that have replaced once-rich organic and vegetated surfaces. Even the topsoil overlaying the compacted engineered fill or historical farmland has been stripped, leaving barren and dry surfaces with no vegetation. The use of impervious materials throughout developed regions of Australia has neglected the diversity in geology.

The standardised approach to civic infrastructure has not considered the diverse geological environments that exist throughout numerous populated regions of Australia, resulting in impervious materials constructed throughout developed regions. Drainage infrastructure has historically been designed to directly discharge stormwater to nearby water bodies such as lakes, rivers, or the ocean as quickly as possible. During Australia’s three consecutive La Ni?a periods, we experienced increased rainfall and intensities, especially during warmer months. Rainfall directly reflected off these impervious environments is significantly warmer than usual.

The conventional impervious urban landscapes, urban heat island effect, and the resulting warmer temperatures can also impact groundwater and land surface temperatures. Impervious surfaces result in increased surface water runoff volumes and higher temperatures can lead to an increase in evaporation rates, reducing the amount of water available for groundwater recharge. This can lead to a reduction in the groundwater table, which can adversely affect both human and natural systems. Additionally, higher land surface temperatures can cause cracking, shifting, and other forms of damage to urban infrastructure such as roads and buildings, leading to costly repairs and maintenance. Higher land surface temperatures can exacerbate the urban heat island effect, leading to even higher temperatures in surrounding areas, which can have long-term impacts on both natural and urban systems.

One potential solution to mitigate these impacts is through the application and integration of Blue-Green Infrastructure . Blue-Green Infrastructure, such as decentralised and distributed systems, rain gardens, passive irrigation tree pits, and other best management practices such as permeable pavements and roof gardens can help reduce the impact of impervious surfaces and increase the extent of healthy soil, water, and vegetation systems - Living Infrastructure - within urban areas, thereby reducing the urban heat island effect, mitigating runoff pollution, reducing flood risk and providing other benefits such as improved air quality and increased biodiversity.

The impacts of rainfall reflected off hot surfaces on water and marine environments can also be extremely significant. The urban heat island effect can directly contribute to the warming of water and marine environments, especially in coastal areas. Rainfall running off impervious surfaces carries pollutants such as oil, grease, heavy metals, and other contaminants, which can have harmful effects on water and marine environments. Additionally, the warmer water temperature can cause changes in the marine ecosystem, including changes in the distribution and behaviour of marine species, increased growth of harmful algae, and the decrease of oxygen levels in the water.

Higher water temperatures can also cause stress to marine organisms, making them more vulnerable to diseases and other stressors. This can impact not only the marine ecosystem but also human activities such as fishing and aquaculture. Warmer water temperatures can contribute to the formation of harmful algal blooms (HABs), which can be toxic to both marine life and humans, causing fish kills, harming shellfish and other aquatic organisms, and causing respiratory issues and other health problems in humans who come into contact with them.

Considering these factors is essential when designing urban landscapes and infrastructure. Taking steps to reduce the urban heat island effect and prevent runoff pollution can help protect water and marine environments, also our communities and ensure their continued health and sustainability.

A recent related LinkedIn post (https://www.dhirubhai.net/posts/owen-richards-6a562638_roads-a-major-problematical-part-of-the-activity-7052950355789156353-DBr9?) responding to Barbara Koffenberger covered strategies for mitigating the issues outlined in this post, which is highly relevant to the topic at hand.

#coastalresilience #climateresilience #naturebasedsolutions #stormwatermanagement #drainagesolutions #greencities #waterconservation #waterforlife #waterislife #naturerestoration #soilhealth #soilhealthmatters #blueeconomy #urbanregeneration #urbanheatisland #porous #decentralization #distributedsystems #environmentalsustainability #environmentalprotection #environmentalawareness #environmentalengineering # Australian Broadcasting Corporation (ABC)

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