Flood of the Tsädh

We were prepared for some flooding, the usual amount. But this was just... there was too much. My house was swept away in minutes, and I haven't seen my neighbours since.

— Na-ochayo farmer

The Flood of the River Tsädh was a devastating natural disaster, beginning in the year 100 Peace. The river, along with its source in Lake Strelish, remained flooded for many years, causing great damage to the countries along their banks and shores.

Cause

Lake Strelish is fed by two rivers, both of which are formed by glaciers high in the eastern mountains. These rivers are at their fullest during the warm summer months, as the glaciers melt. On this particular occasion, in the year 100 Peace, the glacier feeding the southernmost river experienced drastic melting, with a large chunk cracking off. This caused far more water than normal to flow into the lake, resulting in a lot of flooding along the shores.
This was compounded by unseasonal rain and wind, which caused the northern river to also flood its banks. The excess water in Lake Strelish began to flow rapidly downstream into the River Tsädh, and all the way out to the southern seas. The decennial arrival of Diinöl Zdächörri occured during this, bringing with her a sudden change in water level that severely worsened the floods.

Effect

The immediate effect of the floods was widespread destruction along the shores of Lake Strelish and the banks of the River Tsädh. Many homes were completely washed away, with their meagre flood supports failing immediately. Most crops along the river failed to grow in that year, leaving large parts of central Thurásin starving and dependent on outside sources for aid. Lake Strelish was also permanently expanded, largely in the north, resulting in the strange and nigh-labyrinthine bays and inlets of the region.
A dramatic consequence of the flooding was the formation of an entirely new lake - Lake Ozäxa, forming in the valley of the same name. This would have been fine, if not for the fact that the valley was heavily inhabited at the time. In all the era-defining flood, the valley caused the most casualties.

Type

Natural

Decennial Floods

The Diinöl Zdächörri is the patron saint of Lake Strelish and the River Tsädh, credited by the people for having carved the river's path herself. She slumbers at the bottom of the lake, and comes up to the surface once a decade. The displacement of the water, naturally, causes quite a lot of flooding, though usually an amount that can be handled.
Despite the damage she regularly causes, she is still honoured by the people who live around the lake. That her floods bring many nutrients further inland, to farms that miss out during yearly flooding, also helps her appeal.

Flood by Jasper van der Meij