How Can New York, Wuhan, and California Cities Prepare for Flooding?

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Floods is the most common natural disaster, contributing to 44% of worldwide disasters. While they can occur any time or season, spring and fall present the highest risks for flooding due to the large-scale melting of snow and frequency of thunderstorms.

The severity of flash floods and storms in the U.S has increased, thanks to the changing climate. A good example is the Storm Sandy in 2012, which hit New York, forcing the city to spend billions recovering and building storm surge protectors. Similarly, more than 50 people died due to the recent flash floods from heavy rainfall and Hurricane Ida in America’s North East.

That said, the federal government, cities, and local authorities should proactively prepare for floods to minimize damage. Flooding, regardless of the magnitude, can cause serious injuries and fatalities. It can also:

  •     Disrupt transport routes
  •     Pollute sources of drinking water
  •     Cause damage to homes and properties
  •     Cause damage to roads, bridges, and levees due to massive erosion
  •     Disrupt community utility services
  •     Create mudslides and landslides

Measures to Prepare for Flooding

The fatalities, injuries, and damages to homes and businesses caused by flash floods are devastating. With the unfolding realism of climate change, flooding disasters are poised to escalate unless effective proactive measures are taken to mitigate these problems.

Preparing for flash floods requires that cities create an extensive disaster preparedness plan and solutions that account for all possibilities. Ideally, every city’s emergency flood preparedness plan should feature the following four phases;

  1. Mitigation efforts – this includes a review of zones and building codes and extensive vulnerability analysis. Public education and mitigation projects should also be looked into.
  2. Preparedness – cities should develop an emergency preparedness plan and conduct regular emergency exercises to identify loopholes in their plans.
  3. Response – these are efforts directed toward emergency flood management to prevent further damage or loss of life. The primary goal of this phase is to meet city residents’ basic needs.
  4. Recovery – recovery efforts should bridge the gap between the flood emergency and normalcy. Cities should be able to provide temporary shelters, counseling, and reconstruct the damaged buildings.

That said, while cities should carefully evaluate the crucial infrastructure to invest in, they should also focus on nature-based solutions to mitigate the effects of floods. These measures include;

Harvest Rainwater

A lot of polluted floodwaters flow directly from the dirty streets and other avenues into natural waterways. This presents a serious health hazard for human life, wildlife, and the environment. Therefore, cities should prioritize water collection and storage instead of allowing water to flow through the drains.

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Constructing cisterns can hold thousands of liters of rainwater, which can later be used for cleaning, irrigation, and firefighting. An NRDC study of several U.S cities shows that if cities can capture water from heavy rainfalls, they can meet between 21% and 75% of their annual water demands.

Authorities can create sponge cities by harvesting most of the rainwater, a concept popularized in China and other cities that have experienced a high rate of urban flooding. Ideally, a sponge city holds, cleans, and drains flood water naturally. Therefore, instead of directing rainwater away, the city should retain it for various uses.

Green Roofs

Green roofs, roofing materials with vegetation, are increasingly becoming a popular concept in many parts of the world. Apart from its aesthetic beauty, green roofs absorb almost 80% of rainwater, which helps mitigate floods. Roof vegetation reduces rainwater runoff, prevents sewer overflow, minimizes nitrogen pollution from rainwater, and neutralizes acid rains.

That aside, buildings with green roofs help cool the underlying indoor environment. Clustered dark roofs in urban areas create a heat island effect, which can increase city temperatures by up to 2 to 10 degrees. Planting vegetation on building roofs makes indoor temperatures comfortable. Proving this is a 2013 study, which showed that green roofs of Southern California reduced cooling energy demand by 75%.

Build Permeable Pavement

Permeable or porous pavements are drainage systems that allow water to sink through the surface of parking lots or sidewalks instead of allowing water to run through the drains. Permeable pavements allow water to seep through the soil and rocks beneath, where it undergoes natural filtration.

Maintaining parking lots and pavements made from porous materials is cheaper than those made from concrete, asphalt, and other non-permeable materials. Permeable pavements not only reduce the risks of flooding but also reduce maintenance costs.

Construct Rain Gardens

Rain gardens are shallow dams that trap rainwater, allowing soil and vegetation to naturally filter out contaminants and pollutants. Several studies have shown that rain gardens can effectively absorb 30% more rainwater than conventional landscapes. Rain gardens are particularly beneficial if constructed under roof downspouts or flood-prone lawns.

Cities should adopt the use of rain gardens because they are affordable to build, don’t occupy much space, and are attractive in the landscape. Several cities, including Wisconsin, Madison, and Philadelphia, have already constructed them in public areas. Other cities, such as Seattle, offer homeowners generous incentives and rebates for constructing them in their fields.

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Plant More Trees

Increasing the percentage of vegetation cover by planting trees is an effective traditional method of preventing floods. Trees form canopies, which reduce the impact of rainwater on the surface. When rainwater falls to tree canopies, tree leaves, and barks, hold onto the water until it either evaporates or drips slowly to the surface. This slows the speed of water flow and reduces surface runoff.

Separate Rainwater from Sewer Systems

Separating rainwater from the sewer system is another effective way of preventing urban flooding. Cities should start revamping their underground drainage systems to separate sewer systems from rainwater drainage. Doing this makes it easy for cities to manage wastewater treatment plants without being overwhelmed by large amounts of rainwater.

Conclusion

Heavy rainfall and resulting floods can overwhelm towns, communities, and cities within minutes. Therefore, while avoiding floods is impossible, cities should implement resilience measures to mitigate and reduce the impact of floods on homes, commercial buildings, and residents.

While the above measures are effective, authorities should also encourage city residents to prepare for floods individually. They should issue FEMA brochures that guide residents on the steps they should take to stay safe in case of floods. As mentioned, having a detailed emergency plan also helps cities mitigate the effects of flash floods.

Disclaimer: This content does not necessarily represent the views of IWB.

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