Build a Coastal Flood Inundation STAC DEM Evaluator — implementation

## Build
Assess coastal commercial assets against digital elevation models retrieved from STAC catalogs. Model simulated storm surge water level scenarios to calculate structural ground-floor inundation exposure.

## User
Coastal Vulnerability Engineer

## Workflow
1. Parse building perimeter footprints and recorded ground-floor elevations.
2. Retrieve high-resolution DEM raster assets using STAC Item bounding boxes.
3. Simulate storm surge inundation depths across multiple water level scenarios.
4. Compile an asset vulnerability schedule detailing expected inundation depth.

## Interface
Browser-based map interface highlighting building footprints colored by depth of water under chosen surge heights.

## Data
Query public USGS 3DEP elevation STAC items or host mock elevation GeoTIFFs alongside STAC Item JSON files.
Starter examples below are synthetic. They are not downloaded records.

## Source
[STAC specification](https://raw.githubusercontent.com/radiantearth/stac-spec/master/README.md)
Accesses STAC Collection and Item specifications for lidar-derived digital elevation models (DEM) assets.

## Tools
langgraph, rasterio, geopandas.
LangGraph manages stateful cyclic evaluation across multiple storm surge height scenarios and asset batches.
OpenAPI-compatible endpoint or hosted model for generating natural language engineering mitigation summaries.

## Deliverables
Submit runnable source, pinned dependencies, setup commands, a working interface, example outputs, and a recorded end-to-end demo. Include tests and an action log.

## Acceptance
- Correctly extracts minimum elevation values inside building footprint boundaries.
- Computes flood inundation depth as surge water level minus ground elevation.
- Flags structures where inundation depth exceeds zero for a 2-meter surge event.

## Starter Examples
```json
[
  {
    "input": {
      "_record_type": "simplified synthetic app record",
      "building_id": "BLD-MIAMI-101",
      "stac_dem_item_id": "USGS-3DEP-DEM-01",
      "base_elevation_m": 1.4,
      "first_floor_height_m": 0.5,
      "simulated_surge_levels_m": [
        1,
        2,
        3
      ]
    },
    "expected_output": {
      "building_id": "BLD-MIAMI-101",
      "ground_inundation_at_2m": 0.6,
      "first_floor_breached_at_2m": true,
      "vulnerability_tier": "HIGH"
    }
  },
  {
    "input": {
      "_record_type": "simplified synthetic app record",
      "building_id": "BLD-MIAMI-102",
      "stac_dem_item_id": "USGS-3DEP-DEM-02",
      "base_elevation_m": 3.8,
      "first_floor_height_m": 0.5,
      "simulated_surge_levels_m": [
        1,
        2,
        3
      ]
    },
    "expected_output": {
      "building_id": "BLD-MIAMI-102",
      "ground_inundation_at_2m": 0,
      "first_floor_breached_at_2m": false,
      "vulnerability_tier": "MINIMAL"
    }
  }
]
```

## Safety
Simulation results are indicative risk indicators and must not supersede official FEMA Flood Insurance Rate Maps (FIRMs).
Use mock external writes. Require human review before any real deployment.