RavenR (version 2.2.0)

rvn_rvh_cleanhrus: Clean HRU data table.

Description

Takes rvn_rvh_read-generated HRUtable and SBTable and returns cleaned HRUtable with (hopefully) fewer HRUs

Usage

rvn_rvh_cleanhrus(
  HRUtab,
  SBtab,
  area_tol = 0.01,
  merge = FALSE,
  elev_tol = 50,
  slope_tol = 4,
  aspect_tol = 20,
  ProtectedHRUs = c(),
  LockedHRUs = c(),
  LockedSubbasins = c()
)

Value

hru_table

cleaned HRU table as a dataframe

Arguments

HRUtab

table of HRUs generated (typically) by rvn_rvh_read

SBtab

table of Subbasins generated (typically) by rvn_rvh_read

area_tol

percentage of watershed area beneath which HRUs should be removed (e.g., default value of 0.01 would indicate anything smaller than 1 percent of watershed extent should be removed)

merge

TRUE if similar HRUs are to be merged (this can be slow for large models)

elev_tol

elevation difference (in metres) considered similar. only used if merge=TRUE

slope_tol

slope difference (in degrees) considered similar. only used if merge=TRUE

aspect_tol

slope difference (in degrees) considered similar. only used if merge=TRUE

ProtectedHRUs

vector of HRU IDs that are sacrosanct (not to be removed, but may still increase in area)

LockedHRUs

vector of HRU IDs that are locked (not to be modified)

LockedSubbasins

vector of subbasin IDs that are locked (not to be modified).

Author

James R. Craig, University of Waterloo

Details

rvn_rvh_cleanhrus removes HRUs in two ways:

1. it removes all HRUs smaller than the area_tol percentage of total area. Adjacent HRUs in the subbasin are expanded by the lost area to keep the same relative coverage.

2. it consolidates similar HRUs within the same subbasin (those with same land cover, vegetation, soil profile and similar slope, aspect, and elevation)

The ProtectedHRUs allows the specification of HRUs that should not be removed, even if they would otherwise be merged or removed. These HRUs may still increase in size as other HRUs are consolidated.

The LockedHRUs allows for the specification of HRUs that will not change (removed or increase in size), which may be useful for specific land types such as glaciers or water bodies. It is possible that locking HRUs may prevent the script from resizing remaining HRUs within a subbasin, in which case a warning is issued to the user that the area has changed. If this is the case, it is suggested to reduce the area threshold to try and prevent this issue, or consider simply locking some subbasins.

Note that merging can be a computationally expensive process, and for this reason is set as FALSE by default.

See Also

rvn_rvh_read for the function used to read in the HRU and Subbasin data, and rvn_rvh_write to write rvh information to file.

Examples

# read in example rvh file
nith <- system.file("extdata","Nith.rvh",package = "RavenR")
rvh <- rvn_rvh_read(nith)

# number of HRUs in existing configuration
nrow(rvh$HRUtable)

# clean contents (in this case, remove all HRUs covering less than 5% of the total area)
newHRUs <- rvn_rvh_cleanhrus(rvh$HRUtable,rvh$SBtable,area_tol = 0.05, merge=TRUE)

# clean contents but locking urban areas (two HRUs locked)
newHRUs <- rvn_rvh_cleanhrus(rvh$HRUtable,rvh$SBtable,area_tol = 0.05, merge=TRUE,
   LockedHRUs=rvh$HRUtable[rvh$HRUtable$LandUse=="URBAN", "ID"])