At which sea-level rise is each Charleston critical facility first reached?

Spatial AnalysisbeginnerSpatial analysis

Central Charleston's emergency planning team has a list of its critical facilities (hospitals, fire and EMS stations, police stations and schools) and NOAA's screening extents for 1 to 6 ft of sea-level rise. Before it writes flood plans it wants each facility tagged with the first level that reaches it, so that the facilities reached soonest are planned for first and those no level reaches stay on the list as checked. It needs that table as a layer it can map.

Charleston's emergency planning team is screening the critical facilities of central Charleston, South Carolina, against NOAA's sea-level-rise extents, to decide which ones need a flood plan first. For each facility it needs one figure: the lowest sea-level rise, in whole feet, whose extent reaches it, and nothing where none of the six extents does. The team works in ArcGIS Pro 3.7. Any GIS will do: ArcGIS Pro, QGIS or a script. You are graded on what you hand in.

The data

Dataset	Geometry	Fields	What it holds
Critical facilities, central Charleston	Point	`facility_id` (text), `name` (text), `facility_type` (text)	One point per hospital, fire or EMS station, police station and school, at the centre of its building. `facility_type` is `hospital`, `fire_station`, `police` or `school`.
NOAA sea-level-rise extents, 1 to 6 ft	MultiPolygon	`slr_ft` (whole number)	One feature per level, stored highest level first: the area NOAA maps as under water at the highest high tides with that much sea-level rise, today's open water included. Each level's extent covers the extents of the levels below it, apart from slivers narrower than 15 cm that rounding the coordinates to six decimals left along some edges.

Both files are GeoJSON in WGS 84 (EPSG:4326), longitude first. In ArcGIS Pro, bring each one in with JSON To Features and choose its geometry type: Point for the facilities, Polygon for the extents. The Data tab also offers each as a zipped Shapefile, KML and CSV, but a Shapefile field name holds 10 characters, so its copy of the facilities calls two fields facility_i and facility_t: the result needs the full names.

The rules

A level reaches a facility when the facility's point is inside that level's extent or on its edge: the two intersect.
A facility's first level is the lowest slr_ft among the extents that reach it.
A facility that none of the extents reaches keeps slr_ft null (empty), never 0 or -1.
Every facility is in the result exactly once, at its own point, with facility_id, name and facility_type as delivered.
No facility point lies within 3 m of an extent's edge, so no GIS's tolerance changes which extents reach it. The rule is containment, not distance, and both layers share one coordinate system: nothing needs projecting.

Hand in

A GeoJSON FeatureCollection of points in WGS 84 (EPSG:4326), one feature per facility, with these properties:

Property	Type	What it holds
`facility_id`	text	As delivered
`name`	text	As delivered
`facility_type`	text	As delivered
`slr_ft`	whole number, or null	The lowest sea-level rise, in feet, whose extent reaches the facility; null where none does

Other properties a tool adds, such as Join_Count and TARGET_FID, may stay. From ArcGIS Pro, export with Features To JSON and check both Output to GeoJSON and Project to WGS84: both are off by default.

What to submit

Submit: A GeoJSON FeatureCollection of the features you derived.
Required properties: facility_id, name, facility_type, slr_ft
Result geometry: Point
Record key: facility_id

Objectives

Join polygon attributes to points by their spatial relationship, keeping every target feature
Choose the merge rule a one-to-one join applies when several polygons match one point
Tell a facility that no level reaches (null) from one that a level reaches
Export the joined result as GeoJSON in WGS 84

Constraints

These are where the teaching is. Read them twice.

Reached means intersects: the facility's point inside a level's extent or on its edge
slr_ft is the lowest level whose extent reaches the facility, in whole feet; null where none of the extents does, never 0 or -1
Every facility exactly once, at its delivered point, with facility_id, name and facility_type as delivered
A GeoJSON FeatureCollection of points in WGS 84 (EPSG:4326)

Graded requirements

Every facility, once each
The facility fields and the first level reached, under their names
The facilities, returned as points
First sea-level rise that reaches each facility

Modelled on screening-level exposure assessments of critical facilities, such as the City of Charleston's All Hazards Vulnerability & Risk Assessment, which counts critical facilities among the assets it assesses against sea-level rise and coastal flooding (U.S. Climate Resilience Toolkit case study, read 17 October 2026). The extents are NOAA Office for Coastal Management's 'Sea Level Rise Data: 1-10 ft Sea Level Rise Inundation Extent' (InPort item 48106), which NOAA describes as a screening-level tool that shows the scale of potential flooding, not its exact location; the facilities are from the USGS National Structures Dataset, collected for disaster planning and emergency response. The emergency planning team is illustrative. Tool behaviour is as of ArcGIS Pro 3.7, from Esri's pages 'Spatial Join (Analysis Tools)', 'Add Spatial Join (Data Management Tools)', 'Export Features (Conversion Tools)', 'Features To JSON (Conversion Tools)', 'JSON To Features (Conversion Tools)', 'Geoprocessing considerations for shapefile output' and the arcpy 'FieldMap' class; the QGIS equivalent is 'Join attributes by location (summary)' in the QGIS documentation for 3.44 LTR. Kharita is not affiliated with Esri.

Result GeoJSON

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What will be checked

4 scored, 0 informational

Every facility, once each
20%
The facility fields and the first level reached, under their names
10%
The facilities, returned as points
10%
First sea-level rise that reaches each facility
60%