Floods could threaten up to 750,000 in Kenya--UN

* Flooding, landslides from heavy rains threaten 750,000

* Half are Somali refugees living in camps, UNHCR says



GENEVA, Nov 6 (Reuters) - Up to 750,000 people in Kenya, nearly half of them Somali refugees, could be caught up in flooding and landslides from heavy rains expected to peak in November, the United Nations warned on Friday.

U.N. aid agencies have activated contingency plans, bringing food, water treatment chemicals and mosquito nets to flood-prone areas, according to Elisabeth Byrs of the U.N. Office for the Coordination of Humanitarian Affairs (OCHA).

An estimated 4,600 people along the Indian Ocean coast and Kenya's northeastern region have already fled torrential rainfall, forced to seek shelter in schools and with host families, she told a news briefing.

Six people have died in the heavy rains, which the United Nations said were enhanced by the El Nino weather phenomenon. Changing sea temperatures in the Pacific Ocean affect weather around the world by bringing drought to some places, heavy storms or harsh winters to others.

El Nino caused abnormally heavy rainfall in 1997/98 in Kenya, where severe drought has also hampered economic growth this year.

More than 300,000 mainly Somali refugees in two camps in Kenya are among those at risk, the U.N. refugee agency said.

The UNHCR is seeking $2.8 million from donors to make engineering improvements in the camps, Kakuma in northwestern Kenya and Dadaab in the east on the border with Somalia.

"We are also preparing to locate to higher ground within the camps refugees who might be worst affected by the floods, particularly the chronically ill, disabled people, the elderly and children and teenagers on their own," UNHCR spokesman Andrej Mahecic told reporters.

The overcrowded Dadaab complex of three camps was built to hold some 90,000 people but its population has swollen to three times that -- becoming home to more refugees than any other site in the world, according to the UNHCR.

Cholera, a water-borne disease often linked to flooding, dirty water and sanitation problems, has already infected 10,000 people so far this year in Kenya, killing 200, the World Health Organisation (WHO) said on Friday. (Reporting by Stephanie Nebehay; Editing by Matthew Jones)