> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/introduction-1/landscape-units.md).

# Landscape Units

A Landscape Unit (LSU) is a collection of HRUs. It can be equivalent to a subbasin, a floodplain or upland unit, or a grid cell with multiple HRUs. LSUs are currently only used for summarizing landscape outputs. Two files are needed to define which HRUs are part of which LSU: 

* [ls\_unit.def](/io-docs/introduction-1/landscape-units/ls_unit.def.md) specifies which HRUs a LSU contains.
* [ls\_unit.ele](/io-docs/introduction-1/landscape-units/ls_unit.ele.md) lists all HRUs and their corresponding LSU and basin fractions.