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Evacuation_VermontPDF.Rmd
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Evacuation_VermontPDF.Rmd
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---
title: "Evacuation Risks in Vermont"
author: "Marcos Luna and Neenah Estrella-Luna"
date: "`r Sys.Date()`"
output:
bookdown::pdf_document2:
toc: true
toc_depth: 3
number_sections: true
fig_caption: yes
includes:
in_header: my_header.tex
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo=FALSE, message=FALSE, warning=FALSE)
library(tidyverse)
library(sf)
library(tmap)
library(tmaptools)
library(rmapshaper)
library(parallel)
library(tigris)
options(tigris_use_cache = TRUE, tigris_class = "sf")
library(kableExtra)
```
\pagebreak
# Analysis of evacuation-related risks in Vermont
This is an analysis of flood evacuation risks for priority populations in Vermont. In the event of significant inland flooding, evacuation may be required. For individuals and households with limited mobility, either due to inadequate access to transportation options or because of physical limitations, evacuation presents heightened risk. Evacuation may also prove especially difficult for individuals and households due to limited economic resources, difficulty understanding or accessing information, or low trust in official sources of information.
## Analysis of Flood Hazard Exposure in Vermont
```{r FloodData, include=FALSE}
# Analysis of flooding evacuation risks for priority populations in Vermont
# Estimate proportion of area occupied by FEMA flood zones and river corridors
# # Read in flood hazard areas
# vt_nfhza_2852 <- st_read(dsn = "DATA/FEMA/VT/NFHL_50_20161207.gdb", layer = "S_Fld_Haz_Ar", quiet = TRUE) %>%
# filter(!FLD_ZONE %in% c("OPEN WATER","AREA NOT INCLUDED","D") &
# !ZONE_SUBTY %in% c("AREA OF MINIMAL FLOOD HAZARD",
# "AREA WITH REDUCED FLOOD RISK DUE TO LEVEE")) %>%
# mutate(FLD_ZONE = as.character(FLD_ZONE)) %>% # omit unused factor levels
# st_transform(., crs = 2852) %>%
# st_make_valid() %>%
# group_by(FLD_ZONE) %>% # aggregate flood zone polygons
# summarize(count = n()) %>%
# mutate(Area = st_area(.),
# Interval = case_when(
# FLD_ZONE == "A" ~ "100-year",
# FLD_ZONE == "AE" ~ "100-year",
# FLD_ZONE == "AH" ~ "100-year",
# FLD_ZONE == "AO" ~ "100-year",
# FLD_ZONE == "VE" ~ "100-year",
# FLD_ZONE == "X" ~ "500-year")) %>%
# filter(!st_is_empty())
# # save this layer to save time
# saveRDS(vt_nfhza_2852,"DATA/FEMA/VT/vt_nfhza_2852.Rds")
# # load previously process flood layer
# vt_nfhza_2852 <- readRDS("DATA/FEMA/VT/vt_nfhza_2852.Rds")
# download Census TIGERLine hydrography for VT
# # First, extract list of county names to use with tigris::water
# vt_counties <- counties("VT") %>%
# pull(NAME)
# # Next, download water features for each county and rbind to one layer
# vt_awater_sf <- rbind_tigris(
# lapply(
# vt_counties, function(x) area_water(state = "VT", county = x)
# )
# ) %>%
# st_union() %>%
# st_as_sf() %>%
# st_transform(., crs = 2852)
#
# # save time by loading file
# saveRDS(vt_awater_sf, "DATA/FEMA/VT/vt_awater_sf.Rds")
# load water features
vt_awater_sf <- readRDS("DATA/FEMA/VT/vt_awater_sf.Rds")
# # crop flood zones to land areas only
# start_time <- Sys.time()
# vt_nfhza_2852_land <- vt_nfhza_2852 %>%
# crop_shape(., vt_state_sf, polygon = TRUE) %>%
# st_difference(., vt_awater_sf) %>%
# mutate(Area = st_area(.)) %>%
# st_make_valid() # takes about 1.5 hours
# end_time <- Sys.time()
# end_time - start_time
# # save time by just loading file
# saveRDS(vt_nfhza_2852_land, file = "DATA/FEMA/VT/vt_nfhza_2852_land.Rds")
# load cropped flood zones
vt_nfhza_2852_land <- readRDS("DATA/FEMA/VT/vt_nfhza_2852_land.Rds") %>%
mutate(Area = as.numeric(Area))
# read in river corridors layer. downloaded from VT Open Geodata Portal (https://geodata.vermont.gov/datasets/VTANR::river-corridors-august-2019) in December 2020.
rc <- st_read(dsn = "DATA/FEMA/VT/WaterHydro_RiverCorridors",
layer = "WaterHydro_RiverCorridors_poly") %>%
st_transform(., crs = 2852) %>%
st_make_valid()
# erase areas of rc that overlap with nfhza. 51.8 secs
rc_erased <- ms_erase(rc, vt_nfhza_2852_land) %>%
filter(!st_is_empty(.)) %>%
st_make_valid()
# append erased rc to FEMA flood zones to get total area at flood risk. NOTE that order of rbind matters! first, need to harmonize columns so that they match.
rc_erased2 <- transmute(rc_erased, TYPE = "RC")
# harmonize nfhza variables with rc and rbind to create one combined layer
vt_flood <- vt_nfhza_2852_land %>%
transmute(TYPE = Interval) %>%
rename(geometry = SHAPE) %>%
rbind(rc_erased2, .) %>%
filter(!st_is_empty(.)) %>%
st_make_valid()
# erase areas of FEMA flood zones that overlap with river corridors. 68 secs.
fema_erased <- ms_erase(vt_nfhza_2852_land, rc) %>%
filter(!st_is_empty(.)) %>%
st_make_valid()
# Estimate populations exposed to non-overlapping areas of nfhza and rc and to combined areas
load("DATA/ne_layers.rds")
# Extract state census units and convert to projected local CRS EPSG:2852: NAD83(HARN) / Vermont See https://spatialreference.org/ref/epsg/2852/
vt_blkgrp_2852 <- ne_blkgrp_sf %>%
filter(STATE == "Vermont",
!st_is_empty(.)) %>%
st_transform(., crs = 2852)
vt_tracts_2852 <- ne_tracts_sf %>%
filter(STATE == "Vermont",
!st_is_empty(.)) %>%
st_transform(., crs = 2852)
# Extract state boundary
vt_state_sf <- ne_states_sf_cb %>%
filter(NAME == "Vermont") %>%
st_transform(., crs = 2852)
#### Processing in ArcGIS #####
# # Write out block groups for processing in ArcGIS
# vt_blkgrp_2852 %>%
# dplyr::select(GEOID) %>%
# st_write(., "DATA/FEMA/VT/vt_blkgrp_2852.shp", delete_layer = TRUE)
# #
# # repeat for tracts
# vt_tracts_2852 %>%
# dplyr::select(GEOID) %>%
# st_write(., "DATA/FEMA/VT/vt_tracts_2852.shp", delete_layer = TRUE)
#
# # repeat for state boundary
# vt_state_sf %>%
# st_write(., "DATA/FEMA/VT/vt_state_2852.shp", delete_layer = TRUE)
# Use dasymetric mapping to calculate populations within flood zones. Approach follows method used by Qiang (2019) to eliminate unpopulated areas of census polygons and then reallocate populations to developed areas as identified in National Land Cover Dataset (NLCD).
# Perform NLCD raster-to-vector conversion, vector erase/difference, and vector intersections in ArcMap because it takes too long in R.
# In ArcMap:
# Convert NLCD raster to shapefile. Clip to state.
# Isolate undeveloped areas (gridcode NOT 22 - 24).
# Erase areas of vt_blkgrp_2852 and vt_tracts_2852 that overlap with undeveloped areas in NLCD shapefiles. Compute OldArea of erased polygons in sqm to identify area of developed polygons remaining.
# Intersect erased vt_blkgrps and erased vt_tracts with NFHZA and Hurricane evacuation zones. Read back into R.
##### Return to working in R ######
# # read in processed vt_blkgrps and vt_tracts
# st_layers(dsn = "DATA/FEMA/VT")
vt_blkgrps_developed <- st_read(dsn = "DATA/FEMA/VT",
layer = "vt_blkgrps_developed") %>%
st_transform(., crs = 2852) %>%
st_make_valid()
vt_tracts_developed <- st_read(dsn = "DATA/FEMA/VT",
layer = "vt_tracts_developed") %>%
st_transform(., crs = 2852) %>%
st_make_valid()
# # calculate population within total flood area
# # # intersect total flood area with developed block groups. 24 mins.
# # system.time(vt_blkgrps_flood <- vt_blkgrps_developed %>%
# # transmute(GEOID = GEOID,
# # OldArea = as.numeric(st_area(.))) %>%
# # st_intersection(., vt_flood) %>%
# # mutate(NewArea = as.numeric(st_area(.))))
# # # save the output to save time
# # save(vt_blkgrps_flood, file = "DATA/FEMA/VT/vt_blkgrps_flood.Rds")
# load("DATA/FEMA/VT/vt_blkgrps_flood.Rds")
# calculate populations within flood risk areas
# USE PARALLEL PROCESSING
# determine number of cores to use for parallel processing
n.cores <- detectCores()-1
# create parallel cluster nodes
clust <- makeCluster(n.cores)
# use ClusterEvalQ to load needed packages in each cluster
clusterEvalQ(clust, {
library(tidyverse)
library(sf)
library(tmaptools)
})
# export variables to each node for use in processing
clusterExport(clust, varlist = c("vt_flood", "vt_blkgrps_developed"))
# break up data by county for faster processing
# download counties layer
vt_counties <- counties(state = "VT", cb = TRUE) %>%
st_transform(.,crs=2852)
# break up counties into a list to run with parLapply
county_list <- list()
for (i in 1:(nrow(vt_counties))){
county_list[[i]] <- vt_counties[i,]
}
# run in parallel. takes about 1.8 mins; roughly 13x faster than non-parallel (24 mins)!
vt_blkgrps_flood_list <- parLapply(clust, county_list, function(x){
crop_shape(vt_flood, x, polygon = T) %>%
st_intersection(vt_blkgrps_developed, .) %>%
mutate(NewArea = as.numeric(st_area(.)))
} )
stopCluster(clust)
# bring it all together
vt_blkgrps_flood <- do.call(rbind, vt_blkgrps_flood_list) %>%
st_make_valid()
# repeat for tracts
# create parallel cluster nodes
clust <- makeCluster(n.cores)
# use ClusterEvalQ to load needed packages in each cluster
clusterEvalQ(clust, {
library(tidyverse)
library(sf)
library(tmaptools)
})
# export variables to each node for use in processing
clusterExport(clust, varlist = c("vt_flood", "vt_tracts_developed"))
# run in parallel. takes about 6.2 mins; about 8x faster than non-parallel (48 mins)
vt_tracts_flood_list <- parLapply(clust, county_list, function(x){
crop_shape(vt_flood, x, polygon = T) %>%
st_intersection(vt_tracts_developed, .) %>%
mutate(NewArea = as.numeric(st_area(.)))
} )
stopCluster(clust)
# bring it all together
vt_tracts_flood <- do.call(rbind, vt_tracts_flood_list) %>%
st_make_valid()
# allocate populations to intersected areas
vt_blkgrps_flood <- vt_blkgrps_flood %>%
left_join(., st_drop_geometry(vt_blkgrp_2852), by = "GEOID") %>%
filter(!st_is_empty(.)) %>%
mutate(Proportion = as.numeric(NewArea/OldArea),
NewPop = totalpopE*Proportion,
NewMinority = minorityE*Proportion,
NewUnder5 = under5E*Proportion,
NewOver64 = over64E*Proportion,
NewUnder18 = under18E*Proportion,
NewEng_limit = eng_limitE*Proportion,
NewPov = num2povE*Proportion,
NewLths = lthsE*Proportion)
vt_tracts_flood <- vt_tracts_flood %>%
left_join(., st_drop_geometry(vt_tracts_2852), by = "GEOID") %>%
mutate(Proportion = as.numeric(NewArea/OldArea),
NewDisabled = disabledOver18E*Proportion,
NewNoCar = HHnoCarE*Proportion)
# Compute total block group populations within river corridors
vt_flood_blkgrp_df <- vt_blkgrps_flood %>%
st_drop_geometry() %>%
summarize(`Total Pop` = as.integer(sum(NewPop)),
Minority = as.integer(sum(NewMinority)),
`Under 5` = as.integer(sum(NewUnder5)),
`Over 64` = as.integer(sum(NewOver64)),
`Under 18` = as.integer(sum(NewUnder18)),
`Limited English HH` = as.integer(sum(NewEng_limit)),
`Low Income` = as.integer(sum(NewPov)),
`No HS Dip` = as.integer(sum(NewLths))) %>%
gather(key = Group, value = FloodPop)
vt_flood_tracts_df <- vt_tracts_flood %>%
st_drop_geometry() %>%
summarize(`Disabled` = as.integer(sum(NewDisabled)),
`No Car HH` = as.integer(sum(NewNoCar))) %>%
gather(key = Group, value = FloodPop)
# calculate population within river corridors, excluding areas overlapping with FEMA flood zones
# intersect river corridors with developed block groups. about 1 min for block groups; about 3.8 mins for tracts.
vt_blkgrps_rc <- vt_blkgrps_developed %>%
transmute(GEOID = GEOID,
OldArea = as.numeric(st_area(.))) %>%
st_intersection(., rc_erased) %>%
mutate(NewArea = as.numeric(st_area(.)))
vt_tracts_rc <- vt_tracts_developed %>%
transmute(GEOID = GEOID,
OldArea = as.numeric(st_area(.))) %>%
st_intersection(., rc_erased) %>%
mutate(NewArea = as.numeric(st_area(.)))
# allocate populations to intersected areas
vt_blkgrps_rc <- vt_blkgrps_rc %>%
left_join(., st_drop_geometry(vt_blkgrp_2852), by = "GEOID") %>%
filter(!st_is_empty(.)) %>%
mutate(Proportion = as.numeric(NewArea/OldArea),
NewPop = totalpopE*Proportion,
NewMinority = minorityE*Proportion,
NewUnder5 = under5E*Proportion,
NewOver64 = over64E*Proportion,
NewUnder18 = under18E*Proportion,
NewEng_limit = eng_limitE*Proportion,
NewPov = num2povE*Proportion,
NewLths = lthsE*Proportion)
vt_tracts_rc <- vt_tracts_rc %>%
left_join(., st_drop_geometry(vt_tracts_2852), by = "GEOID") %>%
mutate(Proportion = as.numeric(NewArea/OldArea),
NewDisabled = disabledOver18E*Proportion,
NewNoCar = HHnoCarE*Proportion)
# Compute total block group populations within river corridors
vt_rc_blkgrp_df <- vt_blkgrps_rc %>%
st_drop_geometry() %>%
summarize(`Total Pop` = as.integer(sum(NewPop)),
Minority = as.integer(sum(NewMinority)),
`Under 5` = as.integer(sum(NewUnder5)),
`Over 64` = as.integer(sum(NewOver64)),
`Under 18` = as.integer(sum(NewUnder18)),
`Limited English HH` = as.integer(sum(NewEng_limit)),
`Low Income` = as.integer(sum(NewPov)),
`No HS Dip` = as.integer(sum(NewLths))) %>%
gather(key = Group, value = RCPop)
vt_rc_tracts_df <- vt_tracts_rc %>%
st_drop_geometry() %>%
summarize(`Disabled` = as.integer(sum(NewDisabled)),
`No Car HH` = as.integer(sum(NewNoCar))) %>%
gather(key = Group, value = RCPop)
# calculate population within FEMA flood zones, excluding areas overlapping with river corridors
# intersect fema flood zones with developed block groups.
# create parallel cluster nodes
clust <- makeCluster(n.cores)
# use ClusterEvalQ to load needed packages in each cluster
clusterEvalQ(clust, {
library(tidyverse)
library(sf)
library(tmaptools)
})
# export variables to each node for use in processing
clusterExport(clust, varlist = c("fema_erased", "vt_blkgrps_developed"))
# run in parallel. takes about 1 min; roughly 13x faster than non-parallel (13.7 mins)!
vt_blkgrps_nfhza_list <- parLapply(clust, county_list, function(x){
crop_shape(fema_erased, x, polygon = T) %>%
st_intersection(vt_blkgrps_developed, .) %>%
mutate(NewArea = as.numeric(st_area(.)))
} )
stopCluster(clust)
# bring it all together
vt_blkgrps_nfhza <- do.call(rbind, vt_blkgrps_nfhza_list) %>%
st_make_valid()
# repeat for tracts
# create parallel cluster nodes
clust <- makeCluster(n.cores)
# use ClusterEvalQ to load needed packages in each cluster
clusterEvalQ(clust, {
library(tidyverse)
library(sf)
library(tmaptools)
})
# export variables to each node for use in processing
clusterExport(clust, varlist = c("fema_erased", "vt_tracts_developed"))
# run in parallel. takes about 1.9 mins
vt_tracts_nfhza_list <- parLapply(clust, county_list, function(x){
crop_shape(fema_erased, x, polygon = T) %>%
st_intersection(vt_tracts_developed, .) %>%
mutate(NewArea = as.numeric(st_area(.)))
} )
stopCluster(clust)
# bring it all together
vt_tracts_nfhza <- do.call(rbind, vt_tracts_nfhza_list) %>%
st_make_valid()
# allocate populations to intersected areas
vt_blkgrps_nfhza <- vt_blkgrps_nfhza %>%
left_join(., st_drop_geometry(vt_blkgrp_2852), by = "GEOID") %>%
filter(!st_is_empty(.)) %>%
mutate(Proportion = as.numeric(NewArea/OldArea),
NewPop = totalpopE*Proportion,
NewMinority = minorityE*Proportion,
NewUnder5 = under5E*Proportion,
NewOver64 = over64E*Proportion,
NewUnder18 = under18E*Proportion,
NewEng_limit = eng_limitE*Proportion,
NewPov = num2povE*Proportion,
NewLths = lthsE*Proportion)
vt_tracts_nfhza <- vt_tracts_nfhza %>%
left_join(., st_drop_geometry(vt_tracts_2852), by = "GEOID") %>%
filter(!st_is_empty(.)) %>%
mutate(Proportion = as.numeric(NewArea/OldArea),
NewDisabled = disabledOver18E*Proportion,
NewNoCar = HHnoCarE*Proportion)
# Compute total block group populations within fema flood zones
vt_nfhza_blkgrp_df <- vt_blkgrps_nfhza %>%
st_drop_geometry() %>%
summarize(`Total Pop` = as.integer(sum(NewPop)),
Minority = as.integer(sum(NewMinority)),
`Under 5` = as.integer(sum(NewUnder5)),
`Over 64` = as.integer(sum(NewOver64)),
`Under 18` = as.integer(sum(NewUnder18)),
`Limited English HH` = as.integer(sum(NewEng_limit)),
`Low Income` = as.integer(sum(NewPov)),
`No HS Dip` = as.integer(sum(NewLths))) %>%
gather(key = Group, value = FEMAPop)
vt_nfhza_tracts_df <- vt_tracts_nfhza %>%
st_drop_geometry() %>%
summarize(`Disabled` = as.integer(sum(NewDisabled)),
`No Car HH` = as.integer(sum(NewNoCar))) %>%
gather(key = Group, value = FEMAPop)
# join the dfs and calculate populations living in areas that are both exposed to FEMA flood zones AND to river corridors and join with total state populations to calculate percentages
# Compute total tract populations within the state for same groups
vt_tract_flood_pops_df <- vt_tracts_2852 %>%
as.data.frame() %>%
summarize(`Disabled` = sum(disabledOver18E),
`No Car HH` = sum(HHnoCarE)) %>%
gather(key = Group, value = VTPop) %>%
left_join(.,vt_nfhza_tracts_df, by = "Group") %>%
left_join(., vt_rc_tracts_df, by = "Group") %>%
left_join(., vt_flood_tracts_df, by = "Group")
# Compute populations for state,and join with flood pops
vt_FloodPops_df <- vt_blkgrp_2852 %>%
as.data.frame() %>%
summarize(`Total Pop` = sum(totalpopE),
Minority = sum(minorityE),
`Under 5` = sum(under5E),
`Over 64` = sum(over64E),
`Under 18` = sum(under18E),
`Limited English HH` = sum(eng_limitE),
`Low Income` = sum(num2povE),
`No HS Dip` = sum(lthsE)) %>%
gather(key = Group, value = VTPop) %>%
left_join(.,vt_nfhza_blkgrp_df, by = "Group") %>%
left_join(., vt_rc_blkgrp_df, by = "Group") %>%
left_join(., vt_flood_blkgrp_df, by = "Group") %>%
rbind(.,vt_tract_flood_pops_df) %>%
mutate(FEMA_RCpop = FloodPop - (FEMAPop + RCPop), .after = RCPop) %>%
mutate(across(FEMAPop:FloodPop, ~ .x / VTPop * 100, .names = "Pct{.col}"))
vt_towns_sf <- county_subdivisions(state = "VT", cb = TRUE) %>%
st_transform(., crs = 2852)
town_tracts_df <- vt_tracts_2852 %>%
dplyr::select(-GEOID) %>%
st_centroid(.) %>%
st_intersection(vt_towns_sf,.) %>%
as.data.frame() %>%
group_by(NAME) %>%
summarize(TotalDisabled = sum(disabledOver18E, na.rm = TRUE),
TotalOver18 = sum(Over18E, na.rm = TRUE),
TotalNoCar = sum(HHnoCarE, na.rm = TRUE))
townpopsdf <- vt_blkgrp_2852 %>%
dplyr::select(-GEOID) %>%
st_centroid(.) %>%
st_intersection(vt_towns_sf,.) %>%
as.data.frame() %>%
group_by(NAME) %>%
summarize(GEOID = first(GEOID),
TotalPop = sum(totalpopE, na.rm = TRUE),
TotalHH = sum(householdsE, na.rm = TRUE),
TotalLEH = sum(eng_limitE, na.rm = TRUE),
TotalMin = sum(minorityE, na.rm = TRUE),
TotalLowInc = sum(num2povE, na.rm = TRUE),
TotalNoHS = sum(lthsE, na.rm = TRUE),
TotalOver64 = sum(over64E, na.rm = TRUE),
TotalUnder5 = sum(under5E, na.rm = TRUE),
TotalUnder18 = sum(under18E, na.rm = TRUE)) %>%
left_join(., town_tracts_df, by = "NAME")
vt_state_sf_cb <- ne_states_sf_cb %>%
filter(NAME == "Vermont") %>%
st_transform(., crs = st_crs(vt_blkgrp_2852))
# clean up
rm(list = ls(pattern = "_list"))
# # save data for later analysis
save(vt_blkgrps_flood, vt_blkgrps_nfhza, vt_blkgrps_rc, vt_tracts_nfhza,
vt_tracts_flood, vt_tracts_rc, vt_FloodPops_df,
file = "DATA/FEMA/VT/nfhza_census.Rds")
```
In comparison to other part's of New England, relatively little of Vermont's land area is within flood zones. However, a significant proportion of the population are nevertheless exposed to the risk of flooding from overbanking of inland water bodies (e.g., ponds and rivers) as well as fluvial erosion from streams and rivers. Indeed, damage surveys in Vermont have shown that fluvial erosion, not inundation, is the most common natural hazard type in Vermont.
The analysis of flood exposure presented here is based on a combination of the Federal Emergency Management Agency's (FEMA) National Flood Hazard Layer (NFHL), a digital version of FEMA's most recent flood maps,[^NFHL] and river corridors mapped by the Vermont Agency of Natural Resources (ANR).[^ANR] FEMA identifies areas subject to varying levels of flood risk through its Flood Insurance Rate Maps (FIRMs), which are produced for most parts of the country to identify areas subject to flooding. FEMA's FIRMs are a national standard used by all federal agencies for the purposes of requiring and rating the purchase of flood insurance and regulating new development. The ANR's river corridors represent areas surrounding a river that allow for the meandering, floodplain, and the riparian functions necessary to restore and maintain the naturally stable or least erosive form of a river in order to minimize erosion hazards over time. Lands within and immediately abutting a river corridor are at higher risk to fluvial erosion. Population data comes from the American Community Survey (ACS) 2018 5-year estimates at the census tract and block group levels.
A significant proportion of Vermont's population lives near inland water bodies. As a result, a significant proportion of the population lives near or within known flood zones as well as areas subject to fluvial erosion. Figure \@ref(fig:mapNFHZAPop) below shows areas subject to floods with an Annual Exceedance Probability (AEP) of 1% (also known as a '100-year' flood) and areas subject to 0.2% AEP (also known as a '500-year' flood), as well as areas within river corridors. Areas within the 1% AEP flood zone are designated by FEMA as Special Flood Hazard Areas, and development within those zones must be covered by flood insurance. Areas within the 0.2% AEP are not currently regulated, but these areas are nevertheless subject to flood risk under more extreme, albeit less frequent, flooding circumstances. Note that portions of northwest and northeast Vermont are not currently mapped for flooding risk by FEMA.
```{r mapNFHZAdata, include=FALSE}
# Process data for mapping
# Create point layer of major cities for context
# Note cb=FALSE is necessary for extracting centroids from town polygons. Otherwise, if cb=TRUE, cannot extract centroids from multipolygon features.
vt_towns_sf_pts <- county_subdivisions(state = "VT", cb = TRUE) %>%
filter(NAME %in% c("Brattleboro",
"Manchester",
"Rutland",
"Middlebury",
"Montpelier",
"Burlington",
"Stowe",
"Greensboro"),
GEOID != "5002161225") %>% # remove duplicate Rutland point
st_transform(., crs = 2852) %>%
st_centroid(of_largest_polygon = TRUE)
# Create road layer for context
vt_highways <- primary_roads() %>%
filter(FULLNAME %in% c("I- 89","I- 91","I- 93")) %>%
tmaptools::crop_shape(., ne_states_sf_cb) %>%
st_transform(., crs = 2852)
vt_highways2nd <- primary_secondary_roads("VT") %>%
filter(FULLNAME %in% c("US Hwy 2","US Hwy 4","US Hwy 5","US Hwy 7")) %>%
st_transform(., crs = 2852)
# Extract highway segments for labeling
I89roadSegment <- vt_highways %>%
filter(LINEARID == "110492460319")
I91roadSegment <- vt_highways %>%
filter(LINEARID == "110344465713")
I91roadSegment2 <- vt_highways %>%
filter(LINEARID == "1103059124170")
I93roadSegment <- vt_highways %>%
filter(LINEARID == "1105281295268")
USHwy2Segment <- vt_highways %>%
filter(LINEARID == "1105317260813")
USHwy4Segment <- vt_highways %>%
filter(LINEARID == "1104258038927")
USHwy7Segment <- vt_highways %>%
filter(LINEARID == "1106087319624")
# Create custom icons of highway shields
I89 <- tmap_icons(file = "https://upload.wikimedia.org/wikipedia/commons/thumb/f/f4/I-89.svg/200px-I-89.svg.png")
I91 <- tmap_icons("https://upload.wikimedia.org/wikipedia/commons/thumb/9/90/I-91.svg/200px-I-91.svg.png")
I93 <- tmap_icons("https://upload.wikimedia.org/wikipedia/commons/thumb/0/0d/I-93.svg/200px-I-93.svg.png")
Hwy2 <- tmap_icons("https://upload.wikimedia.org/wikipedia/commons/thumb/2/27/US_2.svg/200px-US_2.svg.png")
Hwy4 <- tmap_icons("https://upload.wikimedia.org/wikipedia/commons/thumb/7/71/US_4.svg/200px-US_4.svg.png")
Hwy7 <- tmap_icons("https://upload.wikimedia.org/wikipedia/commons/thumb/9/95/US_7.svg/200px-US_7.svg.png")
# Bring in outline of New York for western boundary
ny_state_sf <- tigris::states(cb = TRUE) %>%
filter(NAME == "New York")
# # Create polygons to show where there are no FEMA maps
# start_time <- Sys.time()
# nofemapolys <- st_read(dsn = "DATA/FEMA/VT/NFHL_50_20161207.gdb",
# layer = "S_FLD_HAZ_AR", quiet = TRUE) %>%
# filter(FLD_ZONE != "AREA NOT INCLUDED") %>%
# group_by() %>%
# summarize() %>% # aggregate all flood zone polygons into one
# st_transform(., crs = st_crs(vt_state_sf)) %>%
# st_make_valid() %>%
# st_difference(vt_state_sf,.) %>% # extract areas with no flood coverage
# st_cast(., "POLYGON") %>% # disaggregate multipolygon feature
# mutate(Area = st_area(.),
# LABEL = "No FEMA\nFlood Data") %>% # calc area of each polygon
# filter(as.numeric(Area)/10^6 > 1000) # remove polygons < 1000km2
# end_time <- Sys.time()
# end_time - start_time #takes about 9.2mins
#
# # save time by loading previously processed file
# saveRDS(nofemapolys,"DATA/FEMA/VT/nofemapolys.Rds")
# load data
nofemapolys <- readRDS("DATA/FEMA/VT/nofemapolys.Rds")
# # Create random points, with 1 point for every 100 people
# vt_totalpop_pts <- vt_blkgrps_developed %>%
# select(NewPop) %>%
# filter(NewPop >= 100) %>%
# st_sample(., size = round(.$NewPop/100)) %>% # create 1 random point for every 100 people
# st_sf(.) %>%
# group_by() %>%
# summarize() # reduce to one multipoint object
# Create a simplified version of NFHZA polygons to speed up mapping
# start_time <- Sys.time()
vt_nfhza_2852_land_simple <- vt_nfhza_2852_land %>%
select(Interval) %>%
st_cast(., "MULTIPOLYGON") %>% # homogenize type
st_cast(., "POLYGON") %>%
st_simplify(., dTolerance = 100) %>% # reduce vertices
st_make_valid() %>%
group_by(Interval) %>%
summarize() %>%
mutate(Area = st_area(.))
# end_time <- Sys.time()
# end_time - start_time
# Create a simplified version of vt_awater_sf to speed up mapping
vt_awater_sf_simple <- vt_awater_sf %>%
st_cast(., "MULTIPOLYGON") %>% # homogenize type
st_cast(., "POLYGON") %>%
st_simplify(., dTolerance = 100) %>% # reduce vertices
st_make_valid() %>%
group_by() %>%
summarize()
rc_simple <- ms_simplify(rc)
```
```{r mapNFHZAPop, fig.align = "center", fig.cap="Flood Zones and River Corridors across Vermont."}
# Map flood risk zones
m1 <- tm_shape(vt_blkgrp_2852, unit = "mi") + tm_fill(col = "white") +
tm_shape(ne_states_sf_cb) + tm_fill(col="white") +
tm_shape(ny_state_sf) + tm_fill(col="white") +
tm_shape(vt_awater_sf_simple) + tm_fill(col = "#e6f3f7") +
# tm_shape(ne_states_sf_cb) + tm_borders() +
# tm_shape(ny_state_sf) + tm_borders() +
# tm_shape(vt_totalpop_pts) + tm_dots(col = "darkgoldenrod3",
# labels = "1 dot = 100 people",
# alpha = 0.6) +
tm_shape(vt_nfhza_2852_land_simple) +
tm_fill(col = "Interval",
palette = c("dodgerblue", "blueviolet"),
labels = c("1% AEP (100-year)", "0.2% AEP (500-year)"),
title = "FEMA Flood Zones",
alpha = 0.6,
border.alpha = 0) +
tm_shape(rc_simple) + tm_fill(col = "forestgreen", alpha = 0.5) +
tm_shape(ne_states_sf_cb) + tm_borders(lwd = 0.2, alpha = 0.8) +
tm_shape(ny_state_sf) + tm_borders(lwd = 0.2, alpha = 0.8) +
tm_shape(vt_highways) + tm_lines(col = "seashell4", lwd = 1.5) +
tm_shape(vt_highways2nd) + tm_lines(col = "seashell4", lwd = 1.5) +
tm_shape(I89roadSegment) +
tm_symbols(shape = I89, border.lwd = NA, size = 0.2) +
tm_shape(I91roadSegment) +
tm_symbols(shape = I91, border.lwd = NA, size = 0.2) +
tm_shape(I91roadSegment2) +
tm_symbols(shape = I91, border.lwd = NA, size = 0.2) +
tm_shape(I93roadSegment) +
tm_symbols(shape = I93, border.lwd = NA, size = 0.2) +
# tm_shape(USHwy2Segment) +
# tm_symbols(shape = Hwy2, border.lwd = NA, size = 0.2) +
# tm_shape(USHwy4Segment) +
# tm_symbols(shape = Hwy4, border.lwd = NA, size = 0.2) +
# tm_shape(USHwy7Segment) +
# tm_symbols(shape = Hwy7, border.lwd = NA, size = 0.2) +
tm_shape(vt_towns_sf_pts) + tm_dots() +
tm_text("NAME", size = 0.5, col = "black",
xmod = 0.7, ymod = 0.2, shadow = TRUE) +
tm_shape(nofemapolys) + tm_fill(col = "gray", alpha = 0.4) +
# tm_text("LABEL", alpha = 0.5) +
tm_scale_bar(breaks = c(0, 10, 20), text.size = 0.5,
position = c(0.6,0.005)) +
# tm_add_legend(type = "fill", col = "darkgoldenrod3",
# alpha = 0.6,
# border.col = "white", border.alpha = 0,
# labels = "1 dot = 100 people",
# title = "Total Population") +
tm_add_legend(type = "fill", col = "gray",
alpha = 0.4,
border.col = "white", border.alpha = 0,
labels = "No FEMA Data",
title = "FEMA Coverage") +
tm_add_legend(type = "fill", col = "forestgreen",
alpha = 0.4,
border.col = "white", border.alpha = 0,
labels = "River Corridor",
title = "VT Agency of Natural Resources") +
tm_layout(title = "Flood Risk",
frame = TRUE, main.title.size = 0.8,
legend.outside = TRUE,
legend.title.size = 0.8,
legend.outside.position = c("right", "top"))
tmap_save(m1, "DATA/FEMA/VT/vt_flood.png",
height = 8, width = 8, units = "in", dpi = 600)
knitr::include_graphics("DATA/FEMA/VT/vt_flood.png")
```
Approximately 1.8% of Vermont's land area falls within FEMA flood zones, while 3.4% of the land area falls within river corridors. Approximately 50% of river corridor areas overlap with FEMA flood hazard areas. A total of 4.4% of land area is prone to FEMA flood risk or fluvial erosion within river corridors. The breakdown by type of risk is presented in Table \@ref(tab:tabNFHZAarea) below.
```{r tabNFHZAarea, echo=FALSE, message=FALSE, warning=FALSE, fig.align = "center", fig.cap="Vermont Land Area within Flood Risk Areas."}
# Total land in VT
vt_area <- as.numeric(vt_state_sf$ALAND)
# Total and percentage of land area at flood risk - non-overlapping FEMA and RC
flood_area_df <- vt_flood %>%
mutate(Area = st_area(.)) %>%
as.data.frame() %>%
group_by() %>%
summarize(SqKm = round(as.numeric(sum(Area)/10^6),1),
SqMi = round(as.numeric(SqKm/2.59),1),
PctArea = paste0(as.character(round(as.numeric(sum(Area)/vt_area*100),1)),"%")) %>%
mutate(`Risk Type` = "TOTAL", .before = "SqKm")
# Total and percentage of land area within river corridors
rc_area_df <- rc %>%
mutate(Area = st_area(.)) %>%
as.data.frame() %>%
group_by() %>%
summarize(SqKm = round(as.numeric(sum(Area)/10^6),1),
SqMi = round(as.numeric(SqKm/2.59),1),
PctArea = paste0(as.character(round(as.numeric(sum(Area)/vt_area*100),1)),"%")) %>%
mutate(`Risk Type` = "River Corridor", .before = "SqKm")
# tally total area within river corridors
rc_area <- rc %>% mutate(Area = as.numeric(st_area(.))/10^6) %>% as.data.frame() %>% summarize(sum(Area)) %>% pull()
# tally area within river corridors, but only for areas where there is also FEMA data. erase river corridors from areas missing fema data and tally remaining river corridor area
rc_infema_area <- nofemapolys %>%
select(-Area) %>%
ms_erase(rc, .) %>%
mutate(Area = as.numeric(st_area(.))/10^6) %>% as.data.frame() %>% summarize(sum(Area)) %>% pull()
# tally area of river corridors not within FEMA flood zones, but only for areas where there is FEMA data
rc_erased_infema_area <- nofemapolys %>%
select(-Area) %>%
ms_erase(rc_erased, .) %>%
mutate(Area = as.numeric(st_area(.))/10^6) %>% as.data.frame() %>% summarize(sum(Area)) %>% pull()
# calculate percentage of river corridors that overlap with FEMA flood zones for areas that contain both FEMA data and river corridor data
rc_overlap_pct <- (rc_infema_area - rc_erased_infema_area)/rc_infema_area*100
# do the inverse
# tally total area within FEMA flood zones
fema_area <- vt_nfhza_2852_land %>% mutate(AreaSqKm = as.numeric(st_area(.))/10^6) %>% as.data.frame() %>% summarize(sum(AreaSqKm)) %>% pull()
# tally area of FEMA flood zones not within river corridors
fema_erased_area <- fema_erased %>% mutate(Area = as.numeric(st_area(.))/10^6) %>% as.data.frame() %>% summarize(sum(Area)) %>% pull()
# calculate percentage of FEMA flood zones within river corridors
fema_overlap_pct <- (fema_area - fema_erased_area)/fema_area*100
# Total and percentage of land area within FEMA flood zones and river corridors
vt_nfhza_2852_land %>%
as.data.frame() %>%
group_by(Interval) %>%
summarize(SqKm = round(as.numeric(sum(Area)/10^6),1),
SqMi = round(as.numeric(SqKm/2.59),1),
PctArea = paste0(as.character(round(as.numeric(sum(Area)/vt_area*100),1)),"%")) %>%
rename(`Risk Type` = Interval) %>%
rbind(rc_area_df) %>%
rbind(flood_area_df) %>%
kable(longtable = T, booktabs = T, format.args = list(big.mark = ','),
caption = "Vermont Land within Flood Areas", digits = 0,
align = "r") %>%
kable_styling(latex_options = c("repeat_header")) %>%
row_spec(4, bold=T, hline_after = F) %>%
footnote(general = "Approximately 50% of river corridor areas overlap with FEMA flood zones.")
```
The proportion of the total state population living within areas prone to flooding or fluvial erosion exceeds the percentage of the land area within flood- or erosion-prone areas. Moreover, exposure varies by population subgroup. Table \@ref(tab:tabNFHZApop) below shows the total and percentages of the general population and various subgroups living within flood-prone areas. Aside from the total population, the largest absolute numbers of subpopulations living within a flood-prone area are low income persons followed by those under 18 and over 64. The latter groups are priority populations who may have limited mobility in the event of an evacuation.
```{r tabNFHZApop, echo=FALSE, message=FALSE, warning=FALSE, fig.align = "center", fig.cap="Vermont Populations Living within Flood Zones or River Corridors."}
# Show table of pops within flood zones
vt_FloodPops_df %>%
mutate(across(PctFEMAPop:PctFloodPop,
~ paste0(as.character(round(.x,1)),"%"))) %>%
arrange(-FloodPop) %>%
mutate(Group = recode(Group, "Minority" = "People of Color",
"No HS Dip" = "No HS Diploma")) %>%
select(Group, VTPop, FEMAPop, PctFEMAPop, RCPop, PctRCPop, FEMA_RCpop,
PctFEMA_RCpop, FloodPop, PctFloodPop) %>%
kable(longtable = T, booktabs = T, format.args = list(big.mark = ','),
caption = "Vermont Populations Living within Flood Zones or River Corridors",
digits = 0, align = "r", col.names = c("Group", "VTPop", "Total", "Pct", "Total", "Pct", "Total", "Pct", "Total", "Pct")) %>%
add_header_above(c(" " = 2, "FEMA Only" = 2, "RC Only" = 2,
"FEMA & RC" = 2,
"All Pops at Risk" = 2)) %>%
kable_styling(latex_options = c("repeat_header"))
```
Some groups are disproportionately exposed to these flood hazards. While approximately 9.9% of the general population are living within FEMA flood zones or river corridors, people in low income households, adults with a disability, and other priority populations, exceed the population average living within these flood-prone areas. These priority populations are disproportionately exposed to flood risk (see Figure \@ref(fig:chartNFHZApop) below).
```{r chartNFHZApop, echo=FALSE, message=FALSE, warning=FALSE, fig.align = "center", fig.cap="Vermont Populations Living within Flood Zones or River Corridors."}
# Create lollipop plot of pops within flood zones
vt_FloodPops_df %>%
mutate(Group = recode(Group, "Minority" = "People of Color",
"No HS Dip" = "No HS Diploma")) %>%
ggplot(aes(x = reorder(Group,PctFloodPop),
y = PctFloodPop)) +
geom_segment(aes(x = reorder(Group,PctFloodPop),
xend = reorder(Group,PctFloodPop),
y = vt_FloodPops_df[1,10], yend = PctFloodPop),
color = "skyblue") +
geom_point(color = "blue", size = 4, alpha = 0.8) +
coord_flip() + xlab("") + ylab("") +
ggtitle("Vermont Populations Living within FEMA Flood Zones\nor River Corridors") +
theme_light() +
theme(panel.grid.major.y = element_blank(),
panel.border = element_blank(),
axis.ticks.y = element_blank()) +
geom_text(aes(x = Group, y = PctFloodPop + 0.2 * sign(PctFloodPop),
label = paste0(round(PctFloodPop,1),"%")),
hjust = 1.8, vjust = -1, size = 3,
color=rgb(100,100,100, maxColorValue=255)) +
scale_y_continuous(labels = function(x) paste0(x, "%")) +
geom_hline(yintercept = vt_FloodPops_df[1,10], linetype = "dashed") +
geom_text(aes(x = "Under 18", y = 11, label = "Above state\naverage"),
color = "gray48") +
geom_text(aes(x = "Under 18", y = 8.5, label = "Below state\naverage"),
color = "gray48") +
expand_limits(y = c(7.5,11.5))
ggsave("images/VT_FEMA_graph.png")
# geom_segment(aes(x = "Total Pop", xend = "Total Pop", y = 5.8, yend = 6.6),
# arrow = arrow(length = unit(0.3,"cm")))
```
The maps below (Figures \@ref(fig:mapNFHZAPopConcern1) and \@ref(fig:mapNFHZAPopConcern2)) show households without a car and low income persons who are disproportionately exposed to flood risk in FEMA flood zones or river corridors. Maps for other priority populations can be found in Figures \@ref(fig:mapNFHZAPopConcern3) to \@ref(fig:mapNFHZAPopConcern8) and breakdowns by municipality in Tables \@ref(tab:tabNFHZANoCar) to \@ref(tab:tabNFHZALEH) in Appendix B.
```{r mapNFHZAPopConcern, include=FALSE}
# # Create a dot density map of transit-dependent populations in flood zone
#
# # create a function to select variable, filter records, and create sample points
# pop2points <- function(sf, x, group){
# x <- enquo(x)
# sf %>%
# select(!!x) %>%
# filter(!!x >= 10) %>%
# st_sample(., size = round(.[[as_label(x)]]/10)) %>%
# st_sf(.) %>%
# mutate(Group = group)
# }
#
# # LimitEngHH_flood_pts <- pop2points(vt_blkgrps_flood,NewEng_limit,"Limited English HH") # no blkgrp with at least 10
#
# NoCarHH_flood_pts <- pop2points(vt_tracts_flood,NewNoCar,"No Car HH")
#
# NoHSdip_flood_pts <- pop2points(vt_blkgrps_flood,NewLths,"No HS Dip")
#
# LowInc_flood_pts <- pop2points(vt_blkgrps_flood,NewPov,"Low Income")
#
# Disabled_flood_pts <- pop2points(vt_tracts_flood,NewDisabled,"Disabled")
#
# Minor_flood_pts <- pop2points(vt_blkgrps_flood,NewMinority,"Minority")
#
# Under5_flood_pts <- pop2points(vt_blkgrps_flood,NewUnder5,"Under 5")
#
# Over64_flood_pts <- pop2points(vt_blkgrps_flood,NewOver64,"Over 64")
#
# Under18_flood_pts <- pop2points(vt_blkgrps_flood,NewUnder18,"Under 18")
#
# # Bring them together
# vt_flood_vulnerable <- rbind(NoCarHH_flood_pts,
# Disabled_flood_pts,
# LowInc_flood_pts,
# Minor_flood_pts,
# Over64_flood_pts,
# Under5_flood_pts,
# Under18_flood_pts,
# NoHSdip_flood_pts) %>%
# # slice(sample(1:n())) %>% # randomise order to avoid bias in plotting order
# group_by(Group) %>%
# summarize()
#
# # clean up pts layers
# rm(list = ls(pattern = "_flood_pts"))
#
# # save time by just loading file
# saveRDS(vt_flood_vulnerable, file = "DATA/FEMA/VT/vt_flood_vulnerable.Rds")
# # load vulnerable point file
vt_flood_vulnerable <- readRDS("DATA/FEMA/VT/vt_flood_vulnerable.Rds")
```
```{r mapNFHZAPopConcern1, fig.align = "center", fig.cap="Households without a Car Living within Flood Zones or River Corridors."}
# create pop subset
flood_sub <- vt_flood_vulnerable %>%
filter(Group == "No Car HH")
# Map over-represented pops and flood zones
m <- tm_layout(bg.color = "#e6f3f7") +
tm_shape(vt_blkgrp_2852, unit = "mi") + tm_fill(col = "white") +
tm_shape(ne_states_sf_cb) + tm_fill(col="white") +
tm_shape(ny_state_sf) + tm_fill(col="white") +
tm_shape(vt_awater_sf_simple) + tm_fill(col = "#e6f3f7") +
tm_shape(flood_sub) +
tm_dots(col = "darkgoldenrod3",
labels = "1 dot = 10 people",
alpha = 0.8) +
# tm_facets(by = "Group",
# ncol = 2,
# free.coords = FALSE) +
tm_shape(vt_nfhza_2852_land_simple) +
tm_fill(col = "Interval",
palette = c("dodgerblue", "blueviolet"),
labels = c("1% AEP (100-year)", "0.2% AEP (500-year)"),
title = "FEMA Flood Zones",
alpha = 0.6,
border.alpha = 0) +
tm_shape(rc_simple) + tm_fill(col = "forestgreen", alpha = 0.5) +
tm_shape(ne_states_sf_cb) + tm_borders(lwd = 0.2) +
tm_shape(ny_state_sf) + tm_borders(lwd = 0.2) +
tm_shape(vt_highways) + tm_lines(col = "seashell4", lwd = 1) +
tm_shape(vt_highways2nd) + tm_lines(col = "seashell4", lwd = 1) +
tm_shape(I89roadSegment) +
tm_symbols(shape = I89, border.lwd = NA, size = 0.1) +
tm_shape(I91roadSegment) +
tm_symbols(shape = I91, border.lwd = NA, size = 0.1) +
tm_shape(I91roadSegment2) +
tm_symbols(shape = I91, border.lwd = NA, size = 0.1) +
tm_shape(I93roadSegment) +
tm_symbols(shape = I93, border.lwd = NA, size = 0.1) +
tm_shape(vt_towns_sf_pts) + tm_dots() +
tm_text("NAME", size = 0.5, col = "black",
xmod = 0.7, ymod = 0.2, shadow = TRUE) +
tm_shape(nofemapolys) +
tm_fill(col = "gray", alpha = 0.4) +
# tm_text("LABEL", alpha = 0.5, size = 0.6) +
tm_scale_bar(breaks = c(0, 10, 20), text.size = 0.5,
position = c(0.6,0.005)) +
tm_add_legend(type = "fill", col = "darkgoldenrod3",
alpha = 0.6,
border.col = "white", border.alpha = 0,
labels = "1 dot = 10 people") +
tm_add_legend(type = "fill", col = "gray",
alpha = 0.4,
border.col = "white", border.alpha = 0,
labels = "No FEMA Data",
title = "FEMA Coverage") +
tm_add_legend(type = "fill", col = "forestgreen",
alpha = 0.4,
border.col = "white", border.alpha = 0,
labels = "River Corridor",
title = "VT Agency of Natural Resources") +
tm_layout(title = "Households\nwithout a Car\nLiving within\nFlood Zones or\nRiver Corridors",
frame = TRUE, main.title.size = 0.8,
legend.outside = TRUE,
legend.title.size = 0.8,
legend.outside.position = c("right", "top"))
tmap_save(m, "DATA/FEMA/VT/VT_flood_vulnerable1.png",
height = 8, width = 8, units = "in", dpi = 600)
knitr::include_graphics("DATA/FEMA/VT/VT_flood_vulnerable1.png")
```
```{r mapNFHZAPopConcern2, fig.align = "center", fig.cap="Low Income Persons Living within Flood Zones or River Corridors."}
# create pop subset
flood_sub <- vt_flood_vulnerable %>%
filter(Group == "Low Income")
# Map over-represented pops and flood zones
m <- tm_layout(bg.color = "#e6f3f7") +
tm_shape(vt_blkgrp_2852, unit = "mi") + tm_fill(col = "white") +
tm_shape(ne_states_sf_cb) + tm_fill(col="white") +
tm_shape(ny_state_sf) + tm_fill(col="white") +
tm_shape(vt_awater_sf_simple) + tm_fill(col = "#e6f3f7") +
tm_shape(flood_sub) +
tm_dots(col = "darkgoldenrod3",
labels = "1 dot = 10 people",
alpha = 0.8) +
# tm_facets(by = "Group",
# ncol = 2,
# free.coords = FALSE) +
tm_shape(vt_nfhza_2852_land_simple) +
tm_fill(col = "Interval",
palette = c("dodgerblue", "blueviolet"),
labels = c("1% AEP (100-year)", "0.2% AEP (500-year)"),
title = "FEMA Flood Zones",
alpha = 0.6,
border.alpha = 0) +
tm_shape(rc_simple) + tm_fill(col = "forestgreen", alpha = 0.5) +