Last time I posted about two case studies of sustainable flood management in Copenhagen and Shanghai (read the blog at: here). In this blog, I will describe more about the green infrastructure elements that can be involved in the flood prevention design.
1. Green roofs / Vertical garden
The first one is green roofs or vertical garden, we will start with the most common thing that we can see on many buildings today. Green roofs or vertical garden is not only enhance the aesthetics of the building, but also it can reduce the urban heat island which is one of the issues from climate change, decrease the capacity of air pollution in the high atmosphere, absorb and reduce some stormwater in the early minutes of the rain event. In addition, it can be urban farming which is not advantage to only flood management, but also the food secure and agriculture sector.
Since it seemed that once the building had been built, the water absorption space would disappear. Therefore, the building must help the city with responsibility by having a private water tank to help reduce the amount of water going into the city’s drainage system. Water tank or water storage areas may also be built as other reservoirs, such as ponds, swimming pools, etc. In some cities also have regulations that buildings must have their own rainwater storage to reduce the capacity of rainwater.
Rain gardens are designed landscape spaces that slow down and reduce the flow rate, total quantity, and pollutant load of runoff from impervious urban areas like driveways, roofs, walkways, lawn areas, and parking lots. Since to create rain gardens need only small spaces, so at present, the concept of rain garden is becoming more popular and accepted at the city level, from being a public park to designing in the private sector such as gardens of buildings and general houses, or corner of parking lots.
Retention ponds are ponds or pools designed with additional storage capacity to attenuate surface runoff during rainfall events. They consist of a permanent pond area with landscaped banks and surroundings to provide additional storage capacity. It will contain water throughout all the time and hold water runoff following storms.
The difference between retention and detention is that the detention temporarily holds water for a short period. So as the case study from Copenhagen last blog, detention space in the city can be multifunctional space that can be designed for a variety of programs, activities, and events in the normal time, but during rain event it can turn to space to reduce peak runoff rates.
The bioretention ponds is quite similar to retention ponds, but the bioretention ponds will be more concerned about ecology such as wastewater treatment, soil treatment, animal habitats. The lists of plant species will be more intend to selected, it depend on soil condition, weather, and what kind of chemical in the contaminated water or soil in that area. Mostly this kind of green infrastructure is very useful to use in the brownfield area or industrial zone.
The forest contains the large capacity of green surface and improve habitats. Since most of the urban areas today used to be a forest before, it means that humans have been destroying animal habitats. Therefore, if those animals cannot adapt themselves to the new environment, they may become extinct. Forest space in the city is not only helping to absorb water, but also solve issues of animal adaptation. However, I think forest idea cannot apply to all of the cities in the world, but that makes some cities have their own unique character.
These are just some examples of green infrastructure that usually use for urban flood management. In addition, there are more green infrastructures including the blue and grey infrastructure that can be integrated with the city to prevent the flood. Some of them can also help to solve the problem in other aspects such as air pollution, soil pollution, energy consumption, etc. In conclusion, in each city, it has its own characteristics and issues, if we selected the appropriate element designs to fit in with the context, we will see the best efficiency of them.
- US EPA. (2019). Soak Up the Rain: Rain Gardens | US EPA. [online] Available at: https://www.epa.gov/soakuptherain/soak-rain-rain-gardens [Accessed 14 Dec. 2019].
- Nwrm.eu. (2015). Retention Ponds | Natural Water Retention Measures. [online] Available at: http://nwrm.eu/measure/retention-ponds [Accessed 14 Dec. 2019].
- Groundwater.org. (n.d.). rain gardens. [online] Available at: https://www.groundwater.org/action/home/raingardens.html [Accessed 14 Dec. 2019].
- En.wikipedia.org. (2019). Rain garden. [online] Available at: https://en.wikipedia.org/wiki/Rain_garden [Accessed 14 Dec. 2019].
- Laramie County Conservation District. (n.d.). Best Management Practices for Stormwater Runoff. [PDF] Available at: https://www.lccdnet.org/wp-content/uploads/Ponds.pdf [Accessed 14 Dec. 2019].
- Prieto, D. (2016). Sustainable Design. [online] Castor.construction. Available at: https://www.castor.construction/single-post/2016/11/01/Sustainable-Design [Accessed 14 Dec. 2019].
- Royal Oak. (n.d.). Rain Garden Program. [online] Available at: https://www.romi.gov/1333/How-Rain-Gardens-Work [Accessed 14 Dec. 2019].
- Vtnews.vt.edu. (2017). Stormwater retention ponds may not protect surface waters from road salt contamination. [online] Available at: https://vtnews.vt.edu/articles/2017/06/cnre-stormwatermanagement.html [Accessed 14 Dec. 2019].
- Mass.gov. (n.d.). Demonstration 3: Permeable Paving Materials and Bioretention in a Parking Lot. [online] Available at: https://www.mass.gov/service-details/demonstration-3-permeable-paving-materials-and-bioretention-in-a-parking-lot [Accessed 14 Dec. 2019].