Tropical Storm Domoina
Encyclopedia
Cyclone Domoina was a tropical cyclone
that hit southern Africa
in early 1984, causing some of the most severe flooding so far recorded in the region.
to the north-east of Madagascar
on 19 January 1984.
The cyclone crossed Madagascar from east to west between Antanarivo and Antsirabe
from 22 January to 24 January 1984 and moved into the Mozambique channel
where it crossed just south of the Comoros
around 26 January 1984.
Domoina made landfall in southern Mozambique
on 28 January 1984,and moved slowly south, with heavy rainfall over northern KwaZulu-Natal
, Mpumalanga
and Swaziland
until 1 February 1984.
The St Lucia lake and estuarine system in northern KwaZulu-Natal, South Africa was struck by Cyclone Domoina on 31 January 1984. Cyclone Domoina reached as far south as Durban
, and associated weather caused severe flooding all along the south coast of KwaZulu-Natal, to Port Edward
.
near the floodplain head. Holiday-makers in Port Edward had to travel inland to Kokstad
, past the southern Drakensberg
, and down through the KwaZulu-Natal Midlands
to return to their homes in the Durban area.
and middle Usutu and Komati
rivers.
The Ingwavuma tributary had 700 millimetres (27.6 in) of rainfall in both the upper and lower reaches.Discharge on the Umfolozi river reached 16000 m3/s, which is about 3 times the 100 year return flood
, while flow velocities of 2.6 m/s were measured.
and Phragmites australis swamps were destroyed in the lower reaches of the Lake St Lucia system by the floodwaters, and mangrove saplings also died from inundation lasting days to weeks. Effects on the fauna included range redistribution of the tanaid Apseudes digitalis, the mysid Mesopodopsis africana, the copepod Pseudodiaptomus stuhlmanni, the polychaete Scololepis squamata and the bivalve Solen cylindraceus, which previously appeared in the tidal channel linking the lake with the sea. A rapid salinity decrease of around 25% had a direct, short-term effect on most components of the benthos
of Lake St Lucia, as well as a long-term effect on the bivalves, particularly Solon cylindraceus, which species was unable to re-establish itself at previous densities. Responses of other species such as penaeid prawns, the crab Scylla serrata
and the sole Solea bleekeri suggested that physiological tolerance, extended larval or juvenile recruitment periods and food source switching minimized long-term flood effects. Indirect long-term effects were noted in the diet of Solea bleekeri, which feeds predominantly on the siphon tips of S. cylindraceus, in that it switched to feeding on other prey at the surface of the benthos.
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
that hit southern Africa
Southern Africa
Southern Africa is the southernmost region of the African continent, variably defined by geography or geopolitics. Within the region are numerous territories, including the Republic of South Africa ; nowadays, the simpler term South Africa is generally reserved for the country in English.-UN...
in early 1984, causing some of the most severe flooding so far recorded in the region.
Meteorological history
Cyclone Domoina began in the Indian OceanIndian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
to the north-east of Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
on 19 January 1984.
The cyclone crossed Madagascar from east to west between Antanarivo and Antsirabe
Antsirabe
Antsirabe is the third largest city in Madagascar and has a population of approximately 183,000. It's the capital of the Vakinankaratra region...
from 22 January to 24 January 1984 and moved into the Mozambique channel
Mozambique Channel
The Mozambique Channel is a portion of the Indian Ocean located between the island nation of Madagascar and southeast Africa, primarily the country of Mozambique. It was a World War II clashpoint during the Battle of Madagascar...
where it crossed just south of the Comoros
Comoros
The Comoros , officially the Union of the Comoros is an archipelago island nation in the Indian Ocean, located off the eastern coast of Africa, on the northern end of the Mozambique Channel, between northeastern Mozambique and northwestern Madagascar...
around 26 January 1984.
Domoina made landfall in southern Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
on 28 January 1984,and moved slowly south, with heavy rainfall over northern KwaZulu-Natal
KwaZulu-Natal
KwaZulu-Natal is a province of South Africa. Prior to 1994, the territory now known as KwaZulu-Natal was made up of the province of Natal and the homeland of KwaZulu....
, Mpumalanga
Mpumalanga
Mpumalanga , is a province of South Africa. The name means east or literally "the place where the sun rises" in Swazi, Xhosa, Ndebele and Zulu. Mpumalanga lies in eastern South Africa, north of KwaZulu-Natal and bordering Swaziland and Mozambique. It constitutes 6.5% of South Africa's land area...
and Swaziland
Swaziland
Swaziland, officially the Kingdom of Swaziland , and sometimes called Ngwane or Swatini, is a landlocked country in Southern Africa, bordered to the north, south and west by South Africa, and to the east by Mozambique...
until 1 February 1984.
The St Lucia lake and estuarine system in northern KwaZulu-Natal, South Africa was struck by Cyclone Domoina on 31 January 1984. Cyclone Domoina reached as far south as Durban
Durban
Durban is the largest city in the South African province of KwaZulu-Natal and the third largest city in South Africa. It forms part of the eThekwini metropolitan municipality. Durban is famous for being the busiest port in South Africa. It is also seen as one of the major centres of tourism...
, and associated weather caused severe flooding all along the south coast of KwaZulu-Natal, to Port Edward
Port Edward, KwaZulu-Natal
Port Edward is a small resort town situated on the south coast of KwaZulu-Natal in South Africa, right on the Eastern Cape Province border.Port Edward is a tourist resort for seasonal visitors from more affluent regions of South Africa...
.
Damage and loss of Life
Cyclone Domoina resulted in the loss of 214 human lives, and the lives of countless livestock and wildlife. Several bridges were washed away by the flood-waters in KwaZulu-Natal, including the bridge connecting the town of St Lucia to the mainland, Major geomorphological changes occurred at the mouth of Lake St Lucia, where all man-made structures were obliterated as the two river channels at the mouth were scoured from 2–3 m (6.6–9.8 ) to 10–14 m (32.8–45.9 ) in depth and widened by up to 300 metres (984.3 ft), while the shoreline between the two channels retreated in places up to 100 metres (328.1 ft), with an estimated 16000000 cubic metres (565,034,659.4 cu ft) of sediment being removed from the lower reaches of the system. Conversely; a large lobe of sediment ~10 kilometres (6.2 mi) long and average 3 kilometres (1.9 mi) wide was deposited on the upper Mfolozi flood-plain as the Mfolozi River avulsed from its former course into the southern Msunduzi RiverMsunduzi River
The Msunduzi River is a river in KwaZulu-Natal, South Africa. It is also known by its anglicised name, the Dusi River. The original name, Msunduzi, is isiZulu.The Msunduzi is a tributary of the Mngeni River.-In Pietermaritzburg:...
near the floodplain head. Holiday-makers in Port Edward had to travel inland to Kokstad
Kokstad, KwaZulu-Natal
Kokstad is a town in the Sisonke District of KwaZulu-Natal Province, South Africa. Kokstad is named after the Griqua chief Adam Kok III who settled here in 1863. Stad is the Dutch and Afrikaans word for city....
, past the southern Drakensberg
Drakensberg
The Drakensberg is the highest mountain range in Southern Africa, rising to in height. In Zulu, it is referred to as uKhahlamba , and in Sesotho as Maluti...
, and down through the KwaZulu-Natal Midlands
KwaZulu-Natal Midlands
The KwaZulu-Natal Midlands is an inland area of KwaZulu-Natal, South Africa that lies outside of Pietermaritzburg but before the Drakensberg mountain range....
to return to their homes in the Durban area.
Hydrology
Storm centres with precipitation exceeding 700 millimetres (27.6 in) over 28 January to 2 February occurred over upper Umfolozi, Mkuze, PongoloPongola River
The Pongola River is a river in South Africa. It is a tributary of the Maputo River. It rises near Utrecht in northern KwaZulu-Natal, flows east through Pongola, is dammed at Jozini, and crosses the Ubombo Mountains; then it flows north towards Mozambique, joining the Maputo River....
and middle Usutu and Komati
Komati River
The Komati River is a river in South Africa, Swaziland and Mozambique. It is long, with a drainage basin in size. Its mean annual discharge is 111 m³/s at its mouth...
rivers.
The Ingwavuma tributary had 700 millimetres (27.6 in) of rainfall in both the upper and lower reaches.Discharge on the Umfolozi river reached 16000 m3/s, which is about 3 times the 100 year return flood
100-year flood
A one-hundred-year flood is calculated to be the level of flood water expected to be equaled or exceeded every 100 years on average. The 100-year flood is more accurately referred to as the 1% annual exceedance probability flood, since it is a flood that has a 1% chance of being equaled or exceeded...
, while flow velocities of 2.6 m/s were measured.
Ecological Consequences
The flooding caused by Domoina on the Umfolozi Rivers destroyed ancient riverine forests. Large areas of mangroveMangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
and Phragmites australis swamps were destroyed in the lower reaches of the Lake St Lucia system by the floodwaters, and mangrove saplings also died from inundation lasting days to weeks. Effects on the fauna included range redistribution of the tanaid Apseudes digitalis, the mysid Mesopodopsis africana, the copepod Pseudodiaptomus stuhlmanni, the polychaete Scololepis squamata and the bivalve Solen cylindraceus, which previously appeared in the tidal channel linking the lake with the sea. A rapid salinity decrease of around 25% had a direct, short-term effect on most components of the benthos
Benthos
Benthos is the community of organisms which live on, in, or near the seabed, also known as the benthic zone. This community lives in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths.Many organisms...
of Lake St Lucia, as well as a long-term effect on the bivalves, particularly Solon cylindraceus, which species was unable to re-establish itself at previous densities. Responses of other species such as penaeid prawns, the crab Scylla serrata
Scylla serrata
Scylla serrata is an economically important crab species found in the estuaries and mangroves of Africa, Australia and Asia. In their most common form, the shell colour varies from a deep, mottled green to very dark brown...
and the sole Solea bleekeri suggested that physiological tolerance, extended larval or juvenile recruitment periods and food source switching minimized long-term flood effects. Indirect long-term effects were noted in the diet of Solea bleekeri, which feeds predominantly on the siphon tips of S. cylindraceus, in that it switched to feeding on other prey at the surface of the benthos.