Flood Risk in Cambodia’s Infrastructure Network: How to Prevent and Mitigate Flood Damage?

• 18 January 2021
• Local News
• 2824 Views

Water is the most significant partner in the construction sector but can also be the worst enemy in destroying construction achievements; as HE Sun Chanthol once said, “Water is the enemy of the road,” which refers to the damaged-infrastructure caused by the recent floods in the kingdom.

Over 3,000 kilometres of local infrastructure, including national roads, provincial roads, red gravel roads, and rural roads, were damaged by the recent floods. In total, at least US$91 million is required to rehabilitate those damages.

To date, the Ministry of Economy and Finance has approved only US$15 million for three priority provinces, which were marked as the most damaged provinces, including Banteay Meanchey, Pursat, and Battambang. As of November, the government has repaired approximately 112km already among the total damages.

Flood & infrastructure

According to ScienceDirect, floods caused by continuous rainfall is a major cause of road damage. Heavy rains cause the soil to flow under the rubber layer, which causes the rubber to lose its strength. Further, when there is heavy rain, the rubber layer will crack and cause bigger holes on the road. Other research has shown that in addition to entering the rubber bottom layer, water also accelerates the size and volume of cracks on the rubber surface.

A road expert and assistant professor at the University of Manit Siddartha Rokade said, “Bitumen is a water-repellent substance, but if there is a leak into the rubber and the duration is long enough, this can also cause big damage in the long run as well.”

“If there is a small hole in the rubber and the rubber will suck in water faster. Then, the size of the hole will be bigger and can also affect the other part of the road,” she added.

Other Factors

The damage to infrastructure is not solely caused by flooding alone; other factors such as urban planning, including sewer management, garbage issues, and transportation arrangements, are also involved.

According to Illinois’s local and regional road engineer William T. Sunley, no matter the type of concrete, rubber, or gravel, the roads will be damaged if the drainage system is not properly designed.

He added that sewers should not be set up after the road is built. Therefore, before beginning any infrastructure development project, the constructor must plan the drainage system properly.

If the drainage system is not set up properly, water can seep into the bottom of the cement or rubber, and when the amount of water increases, the bottom part of the road is more prone to cracking. Combined with the traffic activities, crack sizes will become even larger.

Thus, the constructor must prepare a good drainage system. Spending additional costs on the drainage system will save you from the even higher cost of repairing roads.

Prevention and Mitigation

If there is continuous heavy rain, reducing traffic and the average speed are the first steps. However, if the roads are already flooded, shutting down all the traffic is the best choice.
But what can be done to prevent or minimise the floods as much as possible?

James Harris, Head of Planning and Infrastructure Networking at the Royal Town Planning Institute (RTPI), outlines four rules for sustainable flood risk that can sustain road quality for 50 to 100 years.

First of all, he suggested the Sustainable Urban Drainage System (SUDS). It is a sewer system solution that is similar to natural canals. This method involves digging long slopes with the shoreline, deep furrows in the middle, and plants on both sides. When there is heavy rain, garbage or soil will be caught by the trees and grass beneath.

Other measures include creating a multi-functional greenfield (playground) by the side of the road that can act as a reservoir during floods. Another alternative is planting grass and trees along the side of the road to stabilise the soil and underground water flow.

Floods are natural disasters that we cannot control, but what we can do is to improve the quality of road design, road construction, drainage systems, and importantly control the weight and number of vehicles.

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