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Thursday, December 30, 2021

Why were the floods so bad? Because we were not prepared

 

From Moaz Nair

In contrast to rainfall in some countries, it can rain for days in Malaysia. The annual rainfall on the peninsula is approximately 2,540 mm (100 inches). On Dec 18 alone, Kuala Lumpur exceeded its average monthly rainfall, with certain places in the federal capital recording up to 273mm or 363mm of rainfall.

The continuous rain for three days that caused massive floods in many parts of the country can be considered as one of the country’s worst in the past 50 years. The floods which hit several states in the country have claimed many lives and destroyed countless properties.

Heavy rain and high tides caused rivers to overflow, plunging many urban areas and properties into a deluge of water. Thousands of motorists were stranded as roads were inundated. Thousands were evacuated from their homes. Many were stranded for days without food and drinking water.

Over 54,000 flood victims sought emergency shelter at 334 relief centres in parts of the country with Pahang recording the highest number of flood victims with 29,108 victims followed by Selangor with 23,302 victims.

Power and communications were knocked out by the heavy rain and high tide. Towns and villages were swamped with water causing heavy damage to structures and vegetation. Rain-induced landslides worsened things. Strong wind tore roofs off houses and uprooted trees, especially in the east coast states of the peninsula.

The massive floods highlighted the failure by the authorities to anticipate the consequences despite the weather forecast being available days before the storm.

With the climatic changes taking place, the indirect impact from tropical winds, the fast rate of urbanisation, the clearance of green zones, logging and monsoonal rains, the country will be seeing more massive floods in the future. And these floods are going to be unmanageable.

To be honest, the authorities are not prepared to face severe floods. Neither are the authorities really equipped with the know-how and flood mitigation infrastructure to handle a climactic and man-made disaster of this intensity.

Lesson from the 2004 tsunami

At 7.59am on Dec 26, 2004 a magnitude 9.3 earthquake struck at the bottom of the Indian Ocean, 160 miles west of the island of Sumatra, lasting 10 minutes. It produced a tsunami with forceful energy.

In less than 20 minutes, the tsunami reached the coast of Sumatra and destroyed the northern region of the island, Aceh. The waves reached 80 to 100 feet high, wiping out the entire community there within minutes.

The heavy tsunami and debris of objects brought with it killed around 130,000 to 160,000 of the total population of Aceh, with over 500,000 displaced. One-third of its victims were children.

As Aceh was being devastated, the tsunami wave, moving at a speed of 800 km/h, arrived in Thailand an hour and a half after the quake, pounding Phang Nga and Phuket provinces. It took nearly 5,400 lives there, including 2,000 foreign tourists.

Malaysia was no exception as big waves swept the west coast states and killed 67. The worst affected was Penang with 52 deaths, 12 in Kedah (especially in Langkawi), two in Perak and one in Selangor.

The tsunami that hit Penang and many parts of the northern peninsula was never expected but the damage could have been minimized if the authorities had taken early precautions when the tsunami alert was triggered by the scientific community. But the authorities took for granted that it would not reach the country.

On Dec 16 this year, tens of thousands of people in the Philippines fled their homes and beachfront resorts as super typhoon Rai slammed into the country. The powerful storm was packing maximum sustained winds of 185km/h as it barrelled towards central and southern regions of the vast archipelago. It was the strongest typhoon to hit the country this year.

As for the recent heavy rain and strong wind that hit many parts of Malaysia, the local authorities apparently had failed to predict that the tail wind of typhoon Rai would reach the country.

Thus, never assume that this country is free from these catastrophes, what more with climate change making typhoons more ferocious and unpredictable.

Structural measures needed

In many parts of the country, floods are man-made. Retention ponds or pools designed with additional storage capacity to attenuate surface runoff during rainfall events are being turned into commercial zones. These permanent pond areas with landscaped banks and surroundings are supposed to provide additional storage capacity during heavy rainfall.

Also, severe flooding is the consequence of deforestation and changing land use. Trees can help defend against floods and afforestation can minimise floods. This planting of plants on a large area gives the land a specific grip and can prevent soil erosion and landslides.

Also, the forests create resistance to the flood water which can prevent harm by the floods. Total stoppage to logging activities in the upstream areas would be the most ideal measure to stop mud and debris clogging rivers and streams with the flow of excess water to the lower plains.

Structural measures are generally adopted in many countries to minimize the effects of floods. These include building embankments, flood walls, sea walls, dams and reservoirs, natural detention basins, improving channels and drainage to divert flood waters.

As for the flood prone areas in the country, it’s timely for the authorities to create more diversion channels or flood ways and preserve retention ponds to offer a different route for excess water to flow out, thus mitigating the effects of flooding and restoring rivers to their natural water level.

In some countries, flood diversion areas are uninhabited rural areas or basins that are temporarily flooded in emergencies in order to protect habitable zones.

Shallow trenches are built to redirect flood water to where it can be safely released. Dry streams are built to redirect water and prevent runoff damage. Pervious paving is built in urban areas to allow water to seep through the ground, avoiding the retention of surface water.

Ridges or channels are used to temporarily divert water around or from an area that is under construction. The process includes perimeter control, diversion of water away from corroded slopes, proper drainage system and diversion of sediment-laden water to treatment facilities to overcome flash floods.

Diversion spillways or artificial channels are built for the river to flow into when it rises. These channels move water around an area at risk of flooding and send it either back into the river or into another river further downstream.

Natural flood management may consist of other minor measures to reduce the flow of water. These measures might include using small barriers in ditches and fields, or notches cut into embankments, to divert the water into open land.

Water diversions may cause some environmental disruptions altering the natural habitat and can harm the ecosystem but this would only be temporary as heavy floods in the country usually occur during the monsoon season.

Minimise the damage

So many lives, both humans and animals, were lost, and properties were damaged in the recent floods. These could have been minimised if structural measures had been in place.

There is also no guarantee that the deluge would not happen again or can be fully contained if it happens. But with preparedness and some major structural measures taken, the effects of floods on lives and properties can be lessened. - FMT

Moaz Nair is an FMT reader.

The views expressed are those of the writer and do not necessarily reflect those of MMKtT.

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