PUB tests new portable flood barrier for use in the monsoon season The modular nature of the product enables easy installation at driveways and entrances of residential, commercial and industrial premises

PUB TESTS NEW PORTABLE FLOOD BARRIER FOR USE IN THE MONSOON SEASON

The modular nature of the product enables easy installation at driveways and entrances of residential, commercial and industrial premises.

PUB, Singapore’s National Water Agency, is adding a new flood protection device, Floodgate, to its suite of flood barriers that can be deployed quickly to protect homes and buildings in the event of flash floods, caused by heavy rainstorms during the monsoon season. Floodgate is made from high-strength steel frames, wrapped in a waterproof rubber sleeve. The side panels of the Floodgate barriers can be extended with a wrench to achieve a watertight seal against the doorway. They are available in different sizes to suit apertures with widths ranging from 770 mm to 1520 mm, and weigh between 13 kg to 21 kg, depending on their size. Designed to hold back floodwaters as high as 680 mm, each Floodgate can be deployed by one person within minutes and packed away easily when not in use. Floodgates can be used for wider openings such as the entrances of shopfronts, as units can be linked together to create longer sections. In September 2020, PUB purchased 20 pieces of Floodgates from UK-based Floodgate Limited, for performance testing and validation, with 15 pieces currently on loan to residents at Upper Paya Lebar Road for the monsoon season.

A range of flood protection systems

In 2019, PUB introduced the use of portable flood protection devices such as Dam Easy Flood Panels (DFPs) and Portable Flood Barriers (PFBs), to enhance the nation’s flood response capabilities, and also loaned them out to homes and shophouses in flood-prone and low-lying areas. As at end-December 2020, 65 pieces of DFPs and 155 pieces of PFBs had been loaned out. Users generally found it easy to install them and were assured of the protection they offered during heavy downpours.

More intense rainfall events observed

The wet phase of the Northeast Monsoon in the region typically brings about heavy rainstorms more frequently. Flash floods may occur if the rainstorms temporarily overwhelm the capacity of the drainage system, especially in low-lying areas that are more prone to flooding. The list of flood-prone areas in Singapore can be found at www.pub.gov.sg/drainage/floodmanagement. In 2020, there were seven days when flash floods occurred at various locations in Singapore due to very intense rainfall within a short period of time. The most recent flash flood event, in 2020, occurred on 7 November, when heavy rain overwhelmed the roadside drains along Aljunied Road, causing runoff to accumulate on the road for about 20 minutes. According to the Meteorological Service Singapore, the highest daily total rainfall recorded that day was 100.2 mm at Tanjong Katong. This was the second highest total rainfall recorded in a day for the first half of November 2020. Mr Yeo Keng Soon, PUB's Director of Catchment & Waterways Department, said, “PUB has made significant progress in improving the drainage system over the past 50 years, which greatly reduced the size of flood-prone areas in Singapore, from 3,200 hectares in the 1970s to 28 hectares today. Flash floods, these days, are more localised and typically subside within 30 minutes. However, we are also seeing more frequent rainfall events that are not just bringing increased rainwater but also more intense storms. With climate change, we must be prepared to deal with, and enhance community resilience to, flash flood occurrences, as it is not always possible to widen or deepen our drains to eliminate floods”. “PUB is constantly looking out for new solutions and devices to better enable residents and businesses to respond to flash floods and minimise potential damage to their premises. In the past, we used heavy and bulky one-time-use sandbags against floodwaters. Now, modern flood protection barriers such as Floodgates and Dam Easy Flood Panels can be quickly deployed by residents and shop owners themselves, when there is the possibility of flooding”, he added.

Flood monitoring and stakeholder engagement for the monsoon season

Temporary flood barriers are just one of the measures to better protect residents and businesses. PUB also uses an array of digital technologies and products, such as an extensive network of CCTV cameras, online water level sensors in drains and radar systems, to carry out roundthe-clock weather monitoring, so as to enable quicker response to the needs of flood risk areas. PUB's Quick Response Team (QRT) is also on standby, ready to proceed to areas where flash floods may potentially occur. In addition, PUB actively engages relevant stakeholders to adopt suitable flood protection measures and reminds

them of the need to keep the drainage system clean and free-flowing. For example, PUB officers go door-to-door to issue flood advisories to residents and educate them on what they can do to protect themselves and their homes when a flash flood occurs. PUB also works closely with public agencies and Town Councils to step up the maintenance and cleansing of public drains and vertical drain gratings, so that stormwater can be conveyed away quickly in case of heavy rainfall. Throughout the year, PUB officers also conduct routine inspections at construction sites with major drainage works, at least twice a month, to ensure that proper earth control measures and drainage measures are carried out, and that the drains are free from obstruction. In 2020, PUB inspected 27 such construction sites. During the monsoon season, PUB will also step up its checks at other construction sites around the island. PUB completed checks for 77 such construction sites. Action will be taken against contractors that cause interference with the drainage systems in and around their construction sites.

FEATURES OF THE FLOOD PROTECTION DEVICES

Floodgate

The Floodgate barrier consists of a 25 mm thick steel frame, wrapped in a waterproof 7 mm thick rubber sleeve, that can be installed at doorways or entrances to protect premises from floodwaters. It is able to expand horizontally and vertically, creating a waterproof seal against the doorway. It is also extendable, with the addition of extra units, to help protect wider entrances.

Dam Easy Flood Panel

The Dam Easy Flood Panel (DFP) is an extendable panel with an inflatable seal that provides temporary flood protection for doorways. Each DFP is 0.6 m high and weighs about 20 kg. The panel is reusable and can be adjusted to fit securely within the door reveal ranging from 0.78 m to 1.10 m. The flood panel allows for quick and simple installation without tools and, unlike conventional door barriers, does away with unsightly fixings that damage doorways. To install, the panel is positioned across the doorway and a lever is used to extend the side panels until it touches the doorframe. A pump is then activated to inflate a watertight seal around the panel.

Portable Flood Barrier

The Portable Flood Barrier (PFB) is a self-anchoring flood barrier which, when installed, creates a 0.5 m high dam that helps divert or contain floodwaters away from an area. It is lightweight and is designed for use on firm surfaces such as roads and pavements. Each set of PFBs consists of 10 sections (each weighing about 3.4 kg). Due to its modular nature, it can be set up quickly via a coupling and locking mechanism, to protect buildings and key installations from water damage and

to keep roads open. A complete set of PFBs extends to The Floodgate barrier can be installed at doorways or entrances to protect premises from floodwaters.

The Floodgate barrier is placed between the doorway and the jack is expanded by using a ratchet wrench, to lock in the barrier horizontally (images on top). The wrench is then used to tighten the four bolts at the bottom, to lock in the barrier vertically (image below). After the flood has receded, the four bolts at the bottom are loosened and the jack is compressed to remove the Floodgate barrier from the doorway. Images: Floodgate Limited.

about 6 m in length. No tools are needed for installation and, when not required, the sections can be stacked up, to minimise storage space and for ease of transportation.

Inflatable Flood Bags

Inflatable flood bags are compact and lightweight alternatives to traditional sandbags. These sand-less bags are semi-porous and filled with biodegradable polymer crystals which inflate within minutes, upon contact with water. Inflatable flood bags are easy to move and can be stored away easily. It can absorb up to approximately 23 kg of water. Upon inflation, residents can arrange and stack them up to form as a barrier and reduce the flow of floodwaters into their properties.

All images by PUB, Singapore's National Water Agency, unless otherwise stated.

The Dam Easy Flood Panel (DFP) is an extendable panel that provides temporary flood protection for doorways.

The Portable Flood Barrier (PFB) is self-anchoring and can be used on firm surfaces such as roads and pavements.