(Reuters) -A barrier lake in Taiwan’s mountainous and sparsely populated east coast county of Hualien burst on Tuesday as the outer edges of Super Typhoon Ragasa pounded the island bringing heavy rainfall, killing 15 people so far in a flood.

Here are some facts about the lake.

WHAT IS A BARRIER LAKE?

Barrier lakes are formed when rocks, landslides or other natural blockages make a dam across a river, normally in a valley, blocking and holding back water, hindering or even stopping natural drainage.

WHEN WAS THE HUALIEN LAKE FORMED?

The existence of the lake in its current form was discovered in July after being spotted from satellite monitoring, having been formed when earlier typhoons caused landslides blocking a valley and causing water to pile up behind it.

WHERE IS THE LAKE LOCA

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