## ----include = FALSE----------------------------------------------------------
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  eval = FALSE          # spatial chunks need terra/tmap; not run at build time
)

## ----install------------------------------------------------------------------
# install.packages(c("terra", "tmap"))

## ----dem----------------------------------------------------------------------
# library(terra)
# library(floodflow)
# 
# # Bundled DEM (elevation of a small area, in metres). No download needed.
# dem <- rast(system.file("ex/elev.tif", package = "terra"))
# dem
# 
# # Slope in radians, then as a simple gradient (rise/run) for routing
# slope <- terrain(dem, v = "slope", unit = "radians")
# plot(dem, main = "Bundled elevation model (terra ex/elev.tif)")

## ----roughness----------------------------------------------------------------
# # A stand-in NDVI raster on the same grid as the DEM (values 0-1)
# set.seed(1)
# ndvi <- setValues(dem, runif(ncell(dem), 0, 1))
# 
# # Per-cell Manning's n from vegetation greenness
# rough <- roughness(ndvi, method = "ndvi")
# rough$n            # this is now a SpatRaster of roughness values
# plot(rough$n, main = "Manning's n from vegetation (per cell)")

## ----vulnerability------------------------------------------------------------
# # Three layers on the DEM grid (replace with your real rasters)
# hazard    <- dem / global(dem, "max", na.rm = TRUE)[1, 1]  # deeper where higher-relief, illustrative
# exposure  <- setValues(dem, rpois(ncell(dem), 50))          # population per cell
# vuln      <- setValues(dem, runif(ncell(dem)))              # deprivation index
# 
# risk <- flood_vulnerability(hazard,
#                             exposure = exposure,
#                             vulnerability = vuln)
# risk$risk          # a SpatRaster: relative risk, 0 to 1

## ----map----------------------------------------------------------------------
# fp <- flood_project("example basin", crs = crs(dem))
# fp$vulnerability <- risk
# 
# m <- flood_map(fp, layer = "risk")
# m$engine           # "tmap" when tmap is installed
# m$map              # the interactive map object; print it to view

## ----plot-direct--------------------------------------------------------------
# plot(risk$risk, main = "Flood risk index (Hazard x Exposure x Vulnerability)")

## ----depth-map----------------------------------------------------------------
# # A HAND raster on the DEM grid. For a quick look you can pass the DEM itself
# # (floodflow derives a crude proxy); for accuracy use a true HAND surface, e.g.
# # from whitebox::wbt_elevation_above_stream().
# hand <- dem - global(dem, "min", na.rm = TRUE)[1, 1]
# 
# fp <- flood_project("example basin", crs = crs(dem))
# fp$rainfall <- data.frame(
#   date = seq(as.Date("2020-01-01"), by = "day", length.out = 365),
#   precip_mm = round(runif(365, 0, 20), 1))
# fp <- flood_runoff(fp, engine = "simple")
# fp <- flood_route(fp, area_km2 = 300, hand = hand)   # <- pass the HAND raster
# 
# fp$route$depth_raster            # a SpatRaster of inundation depth
# flood_map(fp, layer = "depth")   # now draws a real inundation map
# plot(fp$route$depth_raster, main = "Inundation depth (m)")

## ----substitute---------------------------------------------------------------
# # Instead of the bundled DEM:
# # dem <- rast(system.file("ex/elev.tif", package = "terra"))
# 
# # use your own:
# dem  <- rast("path/to/your_dem.tif")
# ndvi <- rast("path/to/your_ndvi.tif")
# # ... the rest of the workflow is unchanged.