> 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/theoretical-documentation/section-4-erosion/sediment/sediment-in-lateral-and-groundwater-flow.md).

# Sediment in  Lateral & Groundwater Flow

                      SWAT+ allows the lateral and groundwater flow to contribute sediment to the main channel. The amount of sediment contributed by lateral and groundwater flow is calculated:

                     $$sed\_{lat}=\frac{(Q\_{lat}+Q\_{gw})\*area\_{hru}\*conc\_{sed}}{1000}$$                                                  4:1.5.1

where $$sed\_{lat}$$ is the sediment loading in lateral and groundwater flow (metric tons), $$Q\_{lat}$$ is the lateral flow for a given day (mm H$$*2$$O), $$Q*{gw}$$ is the groundwater flow for a given day (mm H$$*2$$O), $$area*{hru}$$ is the area of the HRU (km$$^2$$), and $$conc\_{sed}$$ is the concentration of sediment in lateral and groundwater flow (mg/L).

Table 4:1-8: SWAT+ input variables that pertain to sediment lag calculations.

| Variable Name | Definition                                                                        | Input File |
| ------------- | --------------------------------------------------------------------------------- | ---------- |
| LAT\_SED      | $$conc\_{sed}$$: Concentration of sediment in lateral and groundwater flow (mg/L) | .hru       |