Engineering Eco Flood Resilient Structures
By: Aimen Ejaz
Abstract
This paper presents a novel interdisciplinary and catchment-based approach for exploring urban flood resilience and recovery. Our research identified a diverse set of adaptation measures for Pakistan that is vulnerable to fluvial and coastal flooding. We drew on methods from social science, urban design, and environmental engineering to gain integrated insights into the opportunities for Pakistan to increase its flood resilience and urban liveability. Results showed that an appropriate balance of social, infrastructural, and urban design responses would be required to retreat from, accommodate and protect against flood risk. One potential solution is the application of physics principles to the design and construction of eco-friendly, flood resilient housing. This paper is part of the Housing Research Center's ‘Urban flood resilience’.
Causes & Trend in Pakistan
Since 14 June 2022, floods in Pakistan have killed 1,717 people. The floods were caused by heavier than usual monsoon rains and melting glaciers that followed a severe heat wave, all of which are linked to climate change. The government of Pakistan estimated losses worth US$30 billion from the flooding.
Pakistan contributes less than 1% of global greenhouse gas emissions but is one of the places most vulnerable to climate change. According to World Weather Attribution, a study by an international team of climate scientists says that global heating made the flooding up to 50% worse and future floods more likely. Deforestation in Pakistan has also been a factor worsening the floods.
1,717 people died, including 639 children, and an additional 12,867 were injured. Over 2.1 million people were left homeless or are living in temporary camps in horrific conditions because of the floods. These are the deadliest floods in Pakistan since 2010, when nearly 2,000 died in flooding, and the deadliest in the world since the 2020 South Asian floods. The UNOSAT United Nations Satellite Centre reported that 75,000km2 had been flooded (around 9% of Pakistan) with USAID stating a maximum floodwater extent of 32,800 square miles (around 10% of Pakistan).
The two southern provinces, Sindh and Baluchistan, each experienced their wettest August ever recorded, receiving 7 and 8 times their usual monthly totals. Floods in Sindh killed 763 people and injured 8,422.10 million people have been displaced in Sindh and 57,496 houses were severely damaged or completely destroyed, mostly in the Hyderabad Division.
Flooding in Baluchistan killed 336 people. In many areas, rainwater infiltrated many homes and made them uninhabitable. Many families were displaced.426,897 houses have either been damaged or completely destroyed.
All these disastrous results have necessitated quick post disaster housing centers.
Post-flood relief housing
After field research, the Housing Research Center at UMT has determined a few key takeaways: housing units made of ashcrete - it has greater compressive strength, flood resilience, and lesser construction time - need to be constructed.
Other materials resistant to water damage include treated wood or metal that can help prevent rot and corrosion, while using waterproof sealants and coatings can protect against water penetration. Additionally, using locally sourced and sustainable materials can help reduce the environmental impact of building construction.
The use of aerodynamic shapes can greatly increase the resilience of a structure to flooding. This is because aerodynamic shapes, such as a teardrop or wing shape, are able to redirect the flow of water around the structure, reducing the amount of force exerted on it. This can be seen in the design of bridge piers, which often incorporate aerodynamic shapes in order to minimize the effects of water flow.
Furthermore, the use of buoyancy principles can also aid in the design of flood resilient housing. This can be achieved through the incorporation of buoyant materials, such as Styrofoam, into the structure of the building. This allows the structure to float, reducing the amount of force exerted on it by the water and decreasing the likelihood of damage.
In terms of eco-friendliness, the use of renewable energy sources is key in the design of flood resilient housing. The incorporation of solar panels, wind turbines, and hydroelectric generators can provide a reliable source of power, even during times of flooding when traditional power sources may be disrupted. This not only reduces the reliance on fossil fuels, but also ensures that essential services such as heating, lighting, and communication can be maintained during a flood.
To avoid such an impact on infrastructure in the future, significant flood resistant improvement can be obtained if the structure has the lowest floors elevated to design flood elevation, which includes wave height relative to a datum determined based on the flood hazard map of the area.
The foundation of flood resistant structures needs to be designed and constructed in such a way that withstands design flood circumstances. It should have adequate capacity to resist flotation, collapse, and permanent lateral movement under the critical load combinations. Furthermore, the foundation design of flood resistant structures should depend on the geotechnical characteristics of soil and strata beneath the foundation and on the soil foundation interaction. As far as foundation walk is concerned, it must withstand flood borne debris impact, hydrodynamic, hydrostatic, wind, soil, and other lateral load that may be imposed during flood design conditions. Apart from lateral loads, foundation walls shall be designed and constructed to support buoyancy and vertical loads that are imposed during design load conditions. Regarding piers, piles, and columns, they are used to raise the structure above design flood elevation in addition to meet requirements of the foundation of flood resistant structure.
Anchorages and connections in the structures need to be designed and executed to withstand the influence of vertical loads, uplift forces, and lateral loads. Beams shall be connected to piles, columns, piers, and foundation walls adequately using suitable means such as bolts and welds. Sufficient anchorages need to be installed for storage tanks, sealed conduits and pipes, and other structures that may suffer from lateral movement and floatation during design flood conditions.
But mere flood resilient engineering wont guard our cities against flood disasters; our urban planning needs to be improved too. Some of the ways our urban spaces can be protected from stormwater flooding are encouraging installation of rainwater tanks on private property, using public spaces for retention, building flood gates and pumps in combination with large-scale retention in the shore area and the catchment, constructing levees around key assets, increasing pipe capacity largely and installing diversion pipes. Areas frequented by floods should be used for other purposes.
Eco Engineering Flood Resilient Structures
An important aspect of eco-engineering flood resilient housing is the incorporation of green infrastructure. This involves designing buildings with features such as green roofs, permeable pavement, and rain gardens that can capture and store stormwater. By using these techniques, eco-engineering flood resilient housing can help to reduce the impact of flooding on the surrounding environment.
Statistics show that eco-engineering flood resilient housing can be highly effective in protecting communities from flooding. In 2019, a study found that eco-friendly building materials were able to reduce flood damage by up to 50%, compared to traditional materials. In addition, the use of green infrastructure was found to be effective in reducing the severity of flooding, with one study showing that it could reduce flood levels by up to 15%.
Furthermore, eco-engineering flood resilient housing can also provide economic benefits. By using sustainable materials and green infrastructure, eco-engineering can help to reduce the cost of flood damage, as well as providing long-term savings on energy and water bills. In addition, eco-engineering can also create new jobs in the construction and engineering sectors, providing a boost to the local economy.
In conclusion, eco-engineering flood resilient housing is a sustainable and cost-effective solution to the problem of flooding. By using eco-friendly materials and green infrastructure, eco-engineering can protect communities from the damaging effects of flooding, while also providing economic benefits.
Using Bamboo to engineer eco flood-resilient structures
Flood resilient bamboo housing designed by architecture students at the University of Karachi (KU)’s Department of Visual Studies presented the economical, environmentally friendly, and mobile design of houses that can be utilized in flood-affected regions and particularly in villages.
Bamboo is a highly sustainable and resilient material that has been used for centuries in construction. Its ability to withstand strong winds and heavy rainfall makes it an ideal choice for building cost effective flood resilient housing.
One of the key benefits of using bamboo in construction is its flexibility. Unlike traditional building materials such as concrete or steel, bamboo can bend and flex without breaking. This allows it to withstand the force of flowing water and shifting ground during a flood.
Additionally, bamboo is a fast-growing plant that can be harvested and replanted repeatedly without damaging the environment. This makes it an environmentally friendly option for housing construction.
Bamboo can also be easily treated with preservatives to make it more resistant to rot and insect damage. This prolongs the lifespan of the material and ensures that it remains strong and durable even in wet conditions.
To create flood resilient housing with bamboo, the first step is to choose a suitable location for the structure. This should be on high ground or on a slope that is not prone to flooding. The bamboo should then be harvested and treated before being used to construct the frame of the building.
The bamboo can be used to create a sturdy, flexible frame for the structure, with the joints held together with natural fibres such as rattan or coconut husk. The walls and roof can then be constructed with bamboo, using a traditional interlocking technique to create a strong and durable structure.
To further enhance the flood resilience of the building, the foundation can be elevated using concrete or wooden stilts. This allows the structure to sit above the floodwater, reducing the risk of damage.
In addition, the building can be designed with features such as large openings and ventilated eaves to allow water to flow freely through the structure. This reduces the pressure on the walls and helps to prevent damage from flooding.
Overall, using bamboo in construction is a sustainable and effective way to create flood resilient housing. Its flexibility and durability make it an ideal choice for building in areas prone to flooding.
Conclusion
Statistics show the importance of implementing these physics principles in the design of flood resilient housing. According to the United Nations Office for Disaster Risk Reduction (UNDRR), floods are the most common natural disaster, accounting for over 40% of all natural disasters worldwide. Additionally, the World Bank estimates that the cost of natural disasters is increasing, with damages reaching $320 billion in 2019 alone. By implementing eco-friendly, flood resilient housing, communities can greatly reduce the damage and financial impact of flooding.
In conclusion, the application of physics principles to the design and construction of eco-friendly, flood resilient housing can greatly improve the resilience of communities to the devastating effects of flooding. Through the use of strong, lightweight materials, aerodynamic shapes, and buoyancy principles, structures can withstand the forces of water and reduce the likelihood of damage. Additionally, the incorporation of renewable energy sources ensures essential services can be maintained during times of flooding. With the increasing frequency and cost of natural disasters, the implementation of these principles is crucial in creating sustainable, resilient communities.