FLOOD RISK ANALYSIS IN ARCGIS PRO

Flood risk analysis in ArcGIS Pro helps identify flood-prone areas using Digital Elevation Model (DEM), land use, rainfall, and hydrological data. Here’s a detailed step-by-step guide:

Step 1: Collect and Prepare Data

You need the following datasets:
✅ Digital Elevation Model (DEM) – Extract from SRTM, ASTER, or LiDAR.
✅ Land Use/Land Cover (LULC) – From Landsat, Sentinel-2, or local sources.
✅ Soil Data – From FAO, USGS, or local geological agencies.
✅ Rainfall Data – From meteorological agencies or TRMM satellite data.
✅ Flood Historical Data – Past flood occurrences (optional but useful).

Prepare the Data in ArcGIS Pro

1. Import all datasets into ArcGIS Pro and check the coordinate system.
2. Clip datasets to the study area using Clip (Raster or Vector) tool.
3. Convert all vector data to raster (if necessary) using Polygon to Raster.

Step 2: Generate Hydrological Features

Use the Spatial Analyst Hydrology Tools to extract drainage features from DEM.

Fill Sinks in DEM

• Open Geoprocessing Tools (Analysis tab → Tools).
• Search for Fill and apply it to remove artificial depressions in DEM.
  

Generate Flow Direction

• Open Flow Direction tool.
• Set the Input DEM (fill).
• Run the tool to generate a flow direction raster.
  

Generate Flow Accumulation

• Open Flow Accumulation tool.
• Use the Flow Direction output as input.
• This calculates water accumulation across the terrain.

Extract Stream Network

• Use Raster Calculator with an appropriate threshold: E.g:(“Flow_Accumulation” > 20000)
• Convert the result to a polyline using Stream to Feature tool.

Step 3: Generate Flood Risk Map

Flood hazard zones depend on slope, elevation, land cover, and rainfall.

Reclassify Elevation & Slope

• Open Slope tool (from DEM) → Generate a slope raster.
• Use Reclassify tool to categorize slope into classes (e.g., Low, Moderate, High).
• Repeat Reclassify for DEM to define low-lying flood-prone areas.

Reclassify Land Use & Soil

• Use Reclassify tool to categorize land use into urban, vegetation, water, bare land.
• Soil types affecting infiltration can also be reclassified.

 Weighted Overlay Analysis

• Open Weighted Overlay tool.
• Add the following layers: ✅ Slope
  ✅ Elevation (DEM Reclassified)
  ✅ Land Use
  ✅ Soil Permeability
  ✅ Flow Accumulation
• Assign weights based on flood contribution (e.g., Slope = 30%, DEM = 20%, Land Cover = 25%, Soil = 25%).
• Run the tool to generate a flood risk map.

Step 4: Identify Vulnerable Areas

Overlay Flood Risk with Population & Infrastructure

• Use Intersect tool to overlay the flood map with roads, buildings, and population layers.
• Use Zonal Statistics to assess affected population.

Create Risk Map

• Classify risk into Low, Moderate, and High Flood Risk Zones.
• Symbolize results for better visualization.

Step 5: Generate Final Flood Risk Maps

• Apply Symbology to display flood risk zones clearly.
• Generate Flood Susceptibility and Vulnerability Maps.
• Export maps in PDF, PNG, or Shapefile format for reports.