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Using ArcMap's ModelBuilder to Produce Flood Analysis

of Tacoma, WA

This map is an output of the Parcel Flood Analysis model created in order to learn the ModelBuilder feature in ArcMap. The model functions as a method for finding land parcels that are at risk of severe or moderate flooding. The inputs required consist of 1) an output directory folder, 2) a parcel input including land use designation, 3) floodplain input in the form of polygons, 4) a land use type field for the field that holds land use information, 5) a floodplain buffer distance (user's choice) and 6) a coordinate system for the feature dataset.

Inputs

Output Directory: 

  • Folder in which the data will be saved

  • User's choice

  • Holds the file geodatabase and feature dataset

​

Parcel Input

  • Shapefile (.shp) of land parcel data

  • Must be polygons

  • Must contain land use designations

  • Automatically imported into the feature dataset

​

Floodplain Input

  • Shapefile (.shp) of floodplain data

  • Must be polygons

  • Automatically imported into the feature dataset

Land Use Type Field

  • Name of attribute field found in parcels data

  • Designates land use types to each parcel of land

  • i.e. commercial, single-family dwelling, etc.

  • Used as category for summary statistics

​

Floodplain Buffer Distance

  • Distance around floodplain polygons for at-risk flood zones

  • User's choice - both distance and unit

  • Used in selection of parcels outside of floodplains but still in danger of flooding due to heavy rains

​

Coordinate System

  • Desired coordinate system

  • User's choice

  • Best set to local standards

Figure 1: Front end of model

The Model

Figure 2: The model as shown in the ModelBuilder editor

This model first sets up a geodatabase and a feature dataset. This is then followed by analysis which includes adding a new "flood class" field to the parcel attribute table. The parcels are then intersected with the floodplains and those falling within floodplains are classified as "2" in the flood class field. The model then switches the selection and buffers the floodplains at a chosen distance. Using the previously selected items (parcels not classified as "2"), the parcels are intersected this time with the buffer zones and those that fall within the buffer zone are classified in the "flood class" field as "1". Finally, two summary statistics tables are created for: 1) parcels directly intersecting floodplains and 2) parcels within the chosen distance of the floodplains. Both tables are organized by land use designation.

Outputs

Figure 3: The output map of projected parcels intersected with floodplains

Figure 4: The output statistics tables by land use for flood class 1 (floodplains) and flood class 2 (flood zones)

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