High tide on the Chao Phraya, 9 to 17 Nov: what to do

Monday morning, 9 November, is the first of nine days of unusually high sea tides in the Chao Phraya. People with a home or shop on the river in Bangkok and six nearby provinces may see water over the banks from morning to midday, without a single drop of rain. The warning comes from announcement No. 15/2569 of the Hydrographic Department of the Royal Thai Navy, dated 5 November, which the Department of Disaster Prevention and Mitigation (DDPM) passed on on 6 November, Thai PBS reported.

A high tide is when the sea pushes into the river mouth harder than usual, so the river drains slowly and rises along its whole length. The announced figures are water levels "above mean sea level", a reference line out at sea, not the depth of water outside your home. What matters is each spot's "critical level". If you picture the bank as the edge of a table, that is the height at which the water reaches the edge, and anything above it spills over.

From 9 to 17 November, morning to midday is the riskiest time

The days and hours split across two measuring points, and riverside residents need them most.

The first is near the Royal Thai Navy headquarters, on the Bangkok side of the river. The Hydrographic Department expects water of about 1.70 to 2.00 metres between 07:30 and 13:30 from 9 to 16 November. The critical level there is 2.00 metres, which means that on the highest days the water will touch the edge, and the DDPM warned that water may seep through the joints of flood walls, piers and drains even if the bank does not overflow.

The second is Phra Chulachomklao Fort in Samut Prakan, at the river mouth. Water is expected at about 1.80 to 1.90 metres between 06:00 and 12:00 from 9 to 17 November. That is above the critical level of 1.70 metres there, which is why the DDPM said water may overflow the banks into low-lying land along the river and canals. Taken together, the hours to watch are about 06:00 to 13:30 every day, and the exact peak of each day should be read from the Hydrographic Department's table, because the tide times shift daily.

The areas to watch are the riverside, canals and communities outside flood walls

In Bangkok, the DDPM asked residents to watch the Chao Phraya and canal areas, especially low-lying land, communities outside flood walls and spots with no permanent barrier. If your home is behind a city flood wall, the risk is lower, but water can still creep in through joints or drain pipes.

Six provinces are on the DDPM's list, with districts named in the announcement: Pathum Thani (Mueang Pathum Thani, Sam Khok), Nonthaburi (Mueang Nonthaburi, Pak Kret, Bang Kruai), Nakhon Pathom (Bang Len, Nakhon Chai Si, Sam Phran), Samut Prakan (Mueang Samut Prakan, Phra Samut Chedi, Phra Pradaeng, Bang Bo), and every district in Samut Sakhon and Samut Songkhram. Beyond homes, the DDPM asked that riverside businesses, such as floating restaurants and construction sites for bank protection walls, be warned to prepare.

This round follows an earlier warning for the same areas from 27 October to 5 November, The Thaiger reported. If water reached your door then, prepare the same way now. For last week's rain and standing water, read our story on the 5 to 9 November flood alert.

Tonight, move your car and your most fragile things higher

Tonight is the easiest moment to act, because the water has not arrived and there is still light to carry things.

Start with the car. If it is parked by the river, or in a lane that has flooded before, move it somewhere higher before Monday morning, such as a flyover, an upper car park or a road well away from the bank, because morning water will arrive before you wake up. Lift ground-floor belongings off the floor by at least one shelf. Put important documents in a waterproof pouch with your phone, a power bank and a torch, as the DDPM advises. Charge your phone and power bank fully before bed, so that if the power is cut in the morning you can still receive alerts.

If you have sandbags, lay them across the doorway and wherever water has seeped in before. Lift cables and appliances off floor sockets. The Metropolitan Electricity Authority (MEA) advises switching off the main breaker once you know water is about to enter the home, because current leaking from a cable or a plugged-in appliance can cause electric shocks. For indoor drains that connect to a canal or the river, find a plug or a bag of sand to block them, because a high tide can push water back up the pipe, which matches the DDPM's warning about water coming through drains.

Every morning, open the tide table before you leave home

The daily water-level table is on the Hydrographic Department's website. The DDPM said provinces and Bangkok must announce high-tide times to residents in advance, but if you do not see one, you can open the table yourself. Each morning, just check what time the water peaks today and plan around it.

If you work or trade on the river, move easy-to-carry goods before 06:00, and do not leave cars or goods on the bank-side walkway. If you must walk by the river or a canal at high water, watch for slippery ground and banks with no railing, and do not let children play near the edge. Once water seeps into the home or shop, switch off the ground-floor breaker before touching a switch or socket, and never touch electrical items with wet hands.

If water gets in or a drain is blocked, call the DDPM on 1784, open 24 hours, or add LINE @1784DDPM. In Bangkok, report standing water or blocked drains to the city hotline, 1555, or on LINE at @traffyfondue, as the city has announced. Save all three in your phone tonight, then open Monday's tide table before you sleep.

Sources

• Thairath: ปภ. แจ้งเตือน 6 จังหวัดภาคกลาง และ กทม. เฝ้าระวังน้ำทะเลหนุนสูง ช่วง 9-17 พ.ย.
• Thai PBS: ปภ.เตือน 6 จังหวัดภาคกลาง และ กทม. เฝ้าระวังน้ำทะเลหนุนสูง 9-17 พ.ย.
• The Thaiger: Chao Phraya high tide may flood Bangkok riverside areas, November 9 to 17
• Hydrographic Department, Royal Thai Navy: water level data
• Metropolitan Electricity Authority: Flooded! Can I still use electricity?