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README.Rmd
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README.Rmd
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---
output: github_document
---
<!-- README.md is generated from README.Rmd. Please edit that file -->
```{r, include = FALSE}
knitr::opts_chunk$set(
collapse = TRUE,
comment = "#>",
fig.path = "man/figures/README-",
out.width = "100%",
tidy.opts=list(width.cutoff=60),
tidy=TRUE
)
library(NFHL)
library(tmap)
library(AOI)
library(dplyr)
library(sf)
```
# NFHL: National Flood Hazard Layers
<!-- badges: start -->
[](http://github.com/badges/stability-badges)
[](#)
[](https://github.com/mikejohnson51/NFHL/actions/workflows/R-CMD-check.yaml)
[](https://github.com/mikejohnson51/NFHL/actions/workflows/pkgdown.yaml)
<!-- badges: end -->
The `NFHL` package provides access data from FEMA's [National Flood Hazards Layers](https://www.fema.gov/national-flood-hazard-layer-nfhl). It integates with the [AOI](https://github.com/mikejohnson51/AOI) package for spatial subsetting workflows and offers functionality to extract and query NFHL layers.
## Installation
You can install the development version of `NFHL` from [GitHub](https://github.com/) with:
``` r
# install.packages("devtools")
remotes::install_github("mikejohnson51/NFHL")
# load libraries
library(NFHL)
library(AOI)
library(dplyr)
```
## Basic Workflow
### Layer IDs
The NFHL contains data for `r nrow(nfhl_meta)` layers. Use `nfhl_meta` to view the list of available layer IDs and names.
```{r, eval = F}
nfhl_meta
```
```{r, echo = F}
print(nfhl_meta)
```
### Layer descriptions
To get detailed information, such as layer name, description, and bounding box, use the `nfhl_describe()` function. For example, let's explore Layer ID 14 (Cross-Sections):
```{r}
nfhl_describe(14)
```
### Extracting Spatial Data
The `nfhl_get()` function retrieves spatial data for a specific layer and area of interest (AOI). The general workflow involves:
1. Defining an AOI.
2. Selecting a layer ID.
3. Extracting spatial data.
```{r}
# Define an AOI around UCSB
AOI <- AOI::aoi_ext("UCSB", wh = 10, units = "km", bbox = TRUE) |>
st_as_sf()
# View at Layer ID 28 description
nfhl_describe(28)$Description
# Extract Flood Hazard Polygons and filter by Special Flood Hazard Areas (SFHA)
floodhazard <- nfhl_get(AOI, 28) %>%
filter(SFHA_TF == "T")
```
```{r, echo = FALSE}
tm_shape(floodhazard) +
tm_fill(col = 'STUDY_TYP') +
tm_borders() +
tm_compass(type = "8star", position = c("right", "bottom")) +
tm_layout(
legend.outside = TRUE,
legend.outside.position = 'bottom',
legend.bg.alpha = 1)
```
## Examples
### Overlaying NHD and NFHL Cross-Sections
Layer ID 14 provides cross-sectional data. Let’s overlay it with hydrographic data from the National Hydrography Dataset (NHD) using the `nhdplusTools` package:
Before we learned that the NFHL offered cross-sectional information (ID: 14). Lets get this data for our UCSB AOI, and overlay it with hydrographic data from NHD.
```{r, message = F, warning = F}
# Get NHD data for the AOI
nhd <- nhdplusTools::get_nhdplus(AOI)
# Extract NFHL Cross-Section data (ID: 14)
cs <- nfhl_get(nhd, 14)
```
```{r echo = FALSE}
tm_shape(cs) +
tm_lines() +
tm_shape(nhd) +
tm_lines(col = "blue") +
tm_compass(type = "8star", position = c("right", "bottom"))
```
## Linking General Structures with NHD
Layer ID 24 provides data on "General Structures." Here, we extract this layer, overlay it with NHD data, and identify structures that cross NHD features.
```{r}
# Describe Layer ID 24
nfhl_describe(24)$Description
# Extract General Structures
stru <- nfhl_get(AOI, 24)
# Identify crossings between structures and NHD data
crossings = st_join(stru,
st_transform(nhd, st_crs(stru)),
join = st_crosses,
left = FALSE) %>%
st_drop_geometry() %>%
mutate(realtionship = "crosses") %>%
select(OBJECTID, realtionship, comid, STRUCT_TYP, LAYER)
# View results
head(crossings)
```
Here, we identified `r nrow(crossings)` structural crossing's in the AOI river networ. For example, bridge 932599 crosses COMID 17596113.
```{r echo = FALSE}
tm_shape(nhd) +
tm_lines(col = "blue") +
tm_shape(stru) +
tm_lines(col = 'STRUCT_TYP', lwd = 5) +
tm_compass(type = "8star", position = c("right", "bottom")) +
tm_layout(
legend.outside = TRUE,
legend.outside.position = 'bottom',
legend.height = .5,
legend.position = c("left","bottom"),
legend.bg.color = "white",
legend.bg.alpha = 1)
```
Here, we identified `r nrow(crossings)` structural crossing's in the AOI river networ. For example, bridge 932599 crosses COMID 17596113.
## Acknowledgements
[Mike Johnson](http://mikejohnson51.github.io) is the Geospatial Science and Technology Lead at NOAA's Office of Water Prediction (OWP). This work contributes to the NSFfunded [Convergence Accelorator Program](https://nsf.gov/awardsearch/showAward?AWD_ID=1937099&HistoricalAwards=false) on [Urban Flooding](https://ufokn.github.io/UFOKN/).
This package is experimental and comes with no guarantee. Pull requests are welcome!!