4 May 2021 Weather Alert: Impact Based Weather Warnings for Western Cape and Namaqua

Please find included several Impact Based Warnings for the Western Cape and Namaqua Region of Northern Cape

Legal notice:
“This warning from SA Weather Service must be communicated as received and may not be altered under any circumstance.
It must be forwarded or communicated in its entirety and no portion hereof may be replicated or copied and distributed.”

Discussion: An upper air driven system is causing considerable rain and showers to develop over the south-western parts of the Western Cape from tomorrow morning spreading eastwards over the rest of the province during the afternoon and evening. Rain continues for the south coastal areas on Thursday and Friday. With this system wave, heights are expected to reach 4.0-5.5m between Cape Columbine and Stilbaai from Wednesday afternoon into Thursday. Along with these higher wave heights, predominant southerly to south-easterly swells are also expected. Strong southerly winds 60-80km/h) is expected along the west and south-west coastal areas from Wednesday early morning spreading to Still Bay by evening and continuing into Thursday. Please note that there is high uncertainty with this system and models have not been consistent. We will continue to monitor the conditions and update warnings.

Impact: Small vessels can possibly be at risk of taking on water and capsizing in a locality. There is also a possibility of difficulty in navigation such as small vessels in a short period and steep waves. Localized disruptions to beachfront activities such as the closure of beaches for swimming can also be expected.

Instruction: Be aware of large unpredictable waves along the coast. Small vessels are advised to seek shelter in harbours, bays or inlets. Be aware of strong rip currents especially during spring tides.

Discussion: An upper air driven system is causing rain and showers to develop over the south-western parts of the Western Cape on Wednesday morning spreading eastwards to the rest of the province during the afternoon and evening. Significant rainfall can be expected in the Overberg, Garden Route and the City of Cape Town from Wednesday afternoon into Thursday, where rainfall accumulations of between 40-60mm reaching up to 80-100mm in the mountainous areas can be expected. A further 05-10mm can be expected on Friday for the same areas. We will continue to monitor the conditions and update warnings.

Impact: Flooding of roads and settlements in both formal and informal settlements are possible that could result in damage to property and infrastructure. Disruption of traffic flow is likely, along with increased motor vehicle accidents, especially in peak hour traffic on Wednesday. Essential services such as water and electricity may be affected. There is a chance for mudslides and rockfalls in susceptible areas.

Instruction: Be cautious on the roads and avoid crossing rivers and swollen streams where water is above your ankles. If trapped in a vehicle during a flood, abandon it and climb to higher ground. In buildings, move valuables to a safe place above the expected flood level. Switch off electricity at the supply point to the building. NEVER drive on a road covered by water. If the vehicle stalls, leave it immediately and seek higher ground. Be especially cautious at night when it’s harder to recognize flood dangers. Listen to the radio or TV for warnings and obey the instructions from disaster management officers.

Discussion: Strong to gale force south-easterly wind of 62-70km/h and gusts up to 80-90km/h is expected from Wednesday late morning along the coastlines between Cape Columbine and Stilbaai, including the Cape Metropole and Overberg during the afternoon. The wind will be at its full force from Wednesday night into Thursday morning, this is the same period when the upper air weather system will be intensifying.

Impact: Strong winds will cause danger to navigation out at sea. Some disruption to operations for small harbours and ports may occur, and also disruptions to beachfront activities are possible. Inland: strong winds will result in dangerous driving conditions, damage to settlements, falling of trees and interruptions to power lines and communications.

Instruction: Stay indoors where possible away from the windows that open towards the severe winds. Be aware of the following: – sudden crosswinds if travelling especially between buildings, fallen trees or power lines and flying debris. Small boats must stay away from the open sea and seek the shelter of a harbour, river estuary or protected bay Parked aircraft should be pointed into the direction of the wind and secured. Ensure that all temporary structures are well anchored.

>>>Legal notice:<<<

“This warning from SA Weather Service must be communicated as received and may not be altered under any circumstance.

It must be forwarded or communicated in its entirety and no portion hereof may be replicated or copied and distributed.”

Report any weather related incidents to the Garden Route Disaster Management Centre at:
044 805 5071.

Weather Alert: Impact-based warning: Rain which could lead to localised flooding- Western Cape Province

In light of this severe weather alert as produced by the South African Weather Service (SAWS) and other centers, the following advisory guidelines are suggested. It is emphasized that these advisories are broad guidelines and should be interpreted considering the local aspects of the region such as soil types, cultural preferences and farming systems. Depending on the particular region, the prioritization of the guidelines will differ. The basic strategy to follow would be to minimize and diversify risk. The province should further simplify, downscale and package the information according to their language preference and if possible use local radio stations and farmers’ days in disseminating the information.

Impact-based warning issued by SAWS valid: 15 March 2021

Yellow (level 1) warning for rain could lead to localized flooding of roads and settlements over the coastal areas of the Overberg and Garden Route Districts in the Western Cape.

Heavy rainfall raises the water level. When the water level is higher than the river banks or the dams, water flows out from the river and flooding occurs.

Preventive measures:

• Construction of proper drainage systems – Drains must be cleaned constantly as they ensure proper water irrigation.
• Mechanical land treatment of slopes such as contour ploughing or terracing to reduce the runoff coefficient.
• Construction of small water and sediment holding areas.
• Construction of floodways (man-made channels to divert floodwater).
• Terracing hillsides to slow flow downhill.

What to do when flooding is forecasted:

Avoid-

• Cutting grass in the rainy season (nutrient depletion).
• Applying fungicides and pesticide (plants and animals).
• Applying N fertilizer (burning of plants) (Nitrogen loss is higher during heavy rain), immediately follows a surface application of fertilizer, especially on sloped areas.
• Dumping fertilizer in one spot can cause the roots below the fertilizer to be burned and die.
• Irrigation (waterlogging can occur, nutrient depletion).

–  Cover Urea licks to prevent them from becoming toxic.

–  Provide shelter for animals (young ones die easily).

–  Leave cultivated areas coarse.

–  Relocate/ move animals to a safe place.

The following are a number of concerns and recommendations:

• Be extra cautious for pest and diseases after the rain has fallen, as high moisture content and high temperatures may trigger these.
• Assume that floodwater contains sewage and might be harmful for human and livestock consumption.
• Before leading livestock across a river, check whether the water level is rising. This is especially necessary if it is already raining, but remembers that there could be a storm further upstream and floodwaters could be on the way

A comprehensive list of strategies can be found in the monthly NAC Advisory. It can be accessed from the following websites: www.dalrrd.gov.za. For more information contact:-

Directorate: Climate Change and Disaster Risk Reduction

Private Bag X93

Pretoria 0001

Tel: 012 319 6775

Email: MittaA@Dalrrd.gov.za

Weather Warning information as received from the Department of Agriculture, Land Reform and Rural Development.