Designing Landscapes that Work with Natural Processes

Article By: Michelle O’Brien

Introduction

Major cities and highly-developed urban areas contain large amounts of impervious surfaces. Resulting elevated levels of stormwater runoff leave cities subject to an increase in extreme flooding events and pollutes nearby waterways. According to the Natural Resource Defense Council, stormwater runoff is estimated to contribute 10 trillion gallons of untreated wastewater into our lakes, rivers, and streams each year.[1] This wastewater contains numerous pollutants including various chemicals, sewage waste, oil and gas, cigarette butts, and fecal bacteria from pet excrement.[2]

Urban architects and planners, environmental groups and scientists are coming up with ways to help major cities lower the risk of extreme flooding events as well as capture pollutants from stormwater runoff.

One way to mitigate stormwater runoff is green infrastructure. Incorporating elements of green infrastructure when designing roads, superhighways, rooftops and sidewalks allows pollutants and excess runoff to percolate through the ground and thus become somewhat filtered before entering the water table. As well, when stormwater infiltrates into the ground via pervious pavement and other forms of green infrastructure, it helps prevent drainage systems from overflowing and therefore helps combat flooding.

Image Source: The Freshwater Trust

Green Infrastructure

Green infrastructure encompasses several practices that reduce the amount of runoff by incorporating permeable surfaces and other plant and soil systems to store, infiltrate and allow for evapotranspiration of surface runoff.[3] These methods involve building surfaces that absorb large amounts of rainfall, therefore greatly reducing the amount of stormwater runoff.[4] Incorporating green roofs, rain gardens, bioswales, and pervious surfaces offers cities a solution to mitigate extreme flooding events while also helping purify the cities’ air.[5] Compared to grey infrastructure, which consists of human constructed dams, seawalls, roads, etc., green infrastructure incorporates mother nature in the forefront of development.[6]

Image Source: Department of Environmental Conservation: New York State

Parks allow for recreation and have been proven to provide healing cognitive benefits, but one major aspect of parks is usually overlooked.[7] Parks and green spaces allow for capturing stormwater runoff and replenish drinking water supplies. When urban development and recreational areas incorporate green infrastructure, runoff is greatly reduced. Green infrastructure can also save money for cities. According to the American Society of Landscape Architects, green infrastructure can reduce costs by a total of 44.1% compared to grey infrastructure.[8] The reduction of grey infrastructure lowers the operation, repair and maintenance, and infrastructure replacement costs by utilizing methods that require less upkeep.[9]

Landscape architect Kotchakorn Voraakhom has designed an exemplary model of a functioning green space in Bangkok. Her design incorporates a detention lawn, green roof, two functioning wetlands, and a retention pond containing electric bikes that filter the water as people cycle through the pond.[10] The Park is designed to mitigate the effects of climate change and help improve urban issues associated with severe flooding events.

Sinking Cities

Countless coastal communities across the world are sinking and experiencing severe flooding. As the average sea level is predicted to rise in the next century, intense flooding events will likely increase across coastal communities. 8 out of the 10 largest cities in the world are along the coast.[11]

These communities are dynamic systems, meaning they change constantly over time. However, current infrastructure is not designed to withstand the events that climate scientists foresee occurring in the future. In large coastal cities such as Bangkok and New York, expanding impacts on structural development by large human populations is clearly apparent. Grey infrastructure has embodied the building design for most major cities, resulting in an alteration of the water cycle.

According to an article by Promchertchoo, Bangkok could be underwater in the next 15 years, as intense storms and floods are expected to intensify as the earth warms and the ice sheets melt.[12] If communities along the coast are to withstand these predictions, they must rebuild and redesign their current infrastructure and incorporate permeable and green areas that work with natural systems, instead of against them. An estimated 40% of the world’s population lives along the coast and will be forced to seek other locations if these efforts fail.[13]

Impervious Surfaces and Flooding

Impervious surfaces increase the rate of flooding since stormwater runoff has limited places to go other than into our drainage systems. When these systems can no longer keep up with the amount of runoff, the often-toxin water backs up the storm drains and floods surrounding areas. Allowing the natural cycle of water penetrating the ground will reduce the intensity of flooding events. This can be facilitated by building green infrastructure even for cities that contain small amounts of ground cover

Every year, the U.S. builds over a million new homes and coverts 16,000 kilometers of land into paved surfaces.[14] The majority of these are impervious surfaces which disrupt both hydrologic and ecological processes while also causing an influx of heat. Impervious surfaces also alter the natural rate of carbon sequestration by eliminating vegetation that uptake carbon from the atmosphere.[15]

Image Source: USGS Impervious Surfaces and Flooding

Conclusion

When cities rely solely on gray infrastructure, large portions of land are paved over and altered in significant ways. However, incorporating and building around the natural processes of mother nature can bring us closer to a cleaner, safer, and more robust environment. We must reimagine the ways we build our cities. Instead of designing “concrete jungles,” we should focus on working with the landscape and incorporate green spaces into urban planning. Incorporating these best management practices will help combat risks and damages associated with climate change. Imagine the amount of water cities could save if investment and involvement in green spaces was considered a fundamental part of urban planning!

References:

[1] Denchak, Melissa. Green Infrastructure: How to Manage Water in a Sustainable Way. NRDC, March 04, 2019. Accessed June 1, 2021, by MO. https://www.nrdc.org/stories/green-infrastructure-how-manage-water-sustainable-way [2] Environmental Protection Agency. (n.d.). EPA. Accessed June 1, 2021 by MO. https://www3.epa.gov/region9/water/npdes/stormwater-feature.html. [3] EPA. Accessed Jun 12, 2021, by MO. https://www.epa.gov/green-infrastructure/what-green-infrastructure [4] Berland, A., Shiflett, S. A., Shuster, W. D., Garmestani, A. S., Goddard, H. C., Herrmann, D. L., & Hopton, M. E. “The role of trees in urban stormwater management. Landscape and Urban Planning.” March 10, 2017. Accessed June 1, 2021 by MO. https://www.sciencedirect.com/science/article/abs/pii/S0169204617300464. [5] Environmental Protection Agency. “Benefits of Green Infrastructure.” EPA, May 28, 2020. Accessed on June 2, 2021 by MO. https://www.epa.gov/green-infrastructure/benefits-green-infrastructure. [6] Conservation. “Green-Gray Infrastructure: Working with nature to protect vulnerable communities” Accessed Jun 22, 2021, by MO. https://www.conservation.org/projects/green-gray-infrastructure [7] Weir, Kristen. Nurtured by nature. American Psychological Association, April 1, 202. Accessed June 4, 2021, by MO. https://www.apa.org/monitor/2020/04/nurtured-nature#:~:text=Cognitive%20benefits&text=And%20experiments%20have%20found%20that,Directions%20in%20Psychological%20Science%2C%20Vol. [8] Gallet, D. “The Value of Green Infrastructure: A Guide to Recognizing Its Economic, Environmental and Social Benefits.” Proceedings of the Water Environment Federation, 2011. Accessed June 4, 2021 by MO. https://doi.org/10.2175/193864711802639741 [9] Gallet, D. “The Value of Green Infrastructure: A Guide to Recognizing Its Economic, Environmental and Social Benefits.” Proceedings of the Water Environment Federation, 2011. Accessed June 4, 2021 by MO. https://doi.org/10.2175/193864711802639741 [10] D'Arcy, Patrick. When Bangkok floods (and it floods a lot), this park does something amazing. TED, Jul 20, 2018. Accessed Jun 6, 2021, by MO. https://ideas.ted.com/when-bangkok-floods-and-it-floods-a-lot-this-park-does-something-amazing/ [11] UN ATLAS OF THE OCEANS. “Human Settlements on the Coast.” Accessed Jun 22, 2021, by MO. http://www.oceansatlas.org/subtopic/en/c/114/ [12] Promchertchoo, P. ASIA'S FUTURE CITIES: Can Bangkok turn back the rising tide and stop sinking? CNA. February 4, 2021. Accessed June 2, 2021 by MO. https://www.channelnewsasia.com/news/asia/asia-s-future-cities-can-bangkok-turn-back-the-rising-tide-and-s-7612754#:~:text=Currently%2C%20Bangkok%20is%20only%200.5%2D2%20metres%20above%20the%20water.&text=A%20study%20by%20Thailand's%20National,some%20areas%20by%20even%20more. [13] US Department of Commerce, N. O. and AA. “What percentage of the American population lives near the coast?” NOAA's National Ocean Service. October 31, 2019. Accessed June 2, 202, by MO. https://oceanservice.noaa.gov/facts/population.html. [14] Elvidge, C. D., Tuttle, B. T., Sutton, P. C., Baugh, K. E., Howard, A. T., Milesi, C., Bhaduri, B., & Nemani, R. “Global Distribution and Density of Constructed Impervious Surfaces.” Sensors (Basel, Switzerland). September 21, 2007. Accessed June 1, 2021 by MO. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3841857/. [15] Elvidge, C. D., Tuttle, B. T., Sutton, P. C., Baugh, K. E., Howard, A. T., Milesi, C., Bhaduri, B., & Nemani, R. “Global Distribution and Density of Constructed Impervious Surfaces.” Sensors (Basel, Switzerland). September 21, 2007. Accessed June 1, 2021 by MO. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3841857/.