Crosslach

Crosslach is a fictional term used in speculative geography and world-building to describe a hydrographic feature in which multiple streams converge at a central hub and radiate into four main branches, forming a cross-shaped watershed. The name combines cross with lach, an archaic or dialect word for a lake or pool, reflecting its water-centered character. In published world-building, crosslaches are typically situated in plateau basins or amphitheater valleys where four drainage divides meet.

Origin and development: The concept appears in late medieval-like cartographic traditions within fictional regions, and has been adopted by writers and game designers to explain irrigation networks and flood management in relatively closed basins.

Structure and variants: A classic crosslach has a central sump or hub where channels meet, with four arms extending north, south, east and west. Variants include the twin-cross (two intersecting crosslaches) and the taper-cross (arms decrease in width away from the hub). Natural crosslaches may form where four rivers meet at a common basin; engineered crosslaches are built for water distribution.

Ecology and economy: The central hub often creates a stable wetland contributing to biodiversity; arms support wetlands along their lengths and furnish water for agriculture and settlements. Sediment management is essential to maintain cross-lach function.

Usage in culture: In fiction, crosslaches symbolize balance and interconnection and are used as settings for trade routes and contested frontiers. They appear in maps, lore, and gameplay as environmental anchors.

See also: Loch, delta, irrigation network, cross confluence.