Demographic Vulnerability Assessment Tool (DVAT)

Step 1 | Step 2 | Step 3 | Step 4 | Additional Concerns

The Coastal Risk Atlas (CRA) vulnerability assessment process can be broken down into three key elements: hazard identification and analysis, demographic identification and analysis, and local infrastructure identification and analysis. Of these three parts, processing tasks are required by the hazard and demographic analysis. The focus of this application is related to the demographic assessment process.

The data selected to use with the CRA comes from the US Census Bureau. The specific file is the SF3 Block Group Demographics. The complete file comes in two parts; the first is the actual (.shp) shapefile, and the second part is a .dbf database file. These two separate parts must be joined together to create one file.

The main objective of this tool is to automate the process of completing a demographic vulnerability assessment when concerned with one or all of the following demographic areas:

• Population of persons living in poverty.
• Population of persons over the age of 65.
• Number of households consisting of a maritally single homeowner who has at least one child.
• Population of persons who do not have a high school diploma.
• Population of persons who do not speak English.
• Number of occupied housing units without a vehicle.
• Number of occupied housing units being rented.
• Number of households receiving public assistance income.
• Number of housing units built before 1970.
• Number of housing units considered as mobile homes.

These ten areas are the basis of the Coastal Risk Atlas demographic vulnerability assessment layers.

The Demographic Vulnerability Assessment Tool (DVAT) allows you to step through the vulnerability assessment process, then select and manipulate the data through an automated click-and-select method. You are given options to choose from such as:

• Select which layer to use.
• Select which demographic concerns to create assessments for.
• Does this layer need to be clipped to another layer?
• Choose a name and location for this new file.
• Select the field names to be used during the calculations.
• Select the upper limits for each class and what vulnerability index is associated with this range of values.
• Do maps need to be created to show these assessments?

The initial page of the DVAT allows you to:

• Select which layer from the map document to use for the assessment. This layer is selected from the first dropdown combo box and should contain all the data necessary.
• Choose which of the demographic concerns vulnerability assessment will be created. Here, each demographic concern has a check box. Each box marked will be included in the vulnerability assessment process.
• The Additional Concerns check box allows you the ability to extend the demographic concerns listed to any type of concern that allows you to find a percentage and then set a vulnerability index based on that percentage value.
• Clip the first layer to another layer, such as a county boundary. A check box denotes whether the clipping function will occur. If the box is marked, you must then choose the layer from the combo box that becomes available. This layer will then be used to clip the layer selected from the first combo box.
• Choose a name and location for this new file. A default name and location is automatically generated in the textbox at the bottom of the form. You may click on the open folder icon to the right of this textbox to bring up a form that will allow you to change either the name of the file, or the location the file will be saved to, or both.

Once all this information is entered into the form, you should click the 'Next' button to take you to the next step. The processing that occurs at this time is first, depending on the clip checkbox, either a copy is simply made of the layer selected in the first combo box, or if the clip checkbox was marked, a copy is made and then clipped to the layer selected in the second combo box. Either way, the new file is saved to the directory and as the name specified in the textbox at the bottom of the form.





In this step, you will be selecting the useable fields from the selected feature layer's attribute table to be used in the percent calculations. The top of the form has text explaining what the certain areas of the form are, and what they are used for. For each demographic concern checked in Step One, a tab is opened in this step. Each tab contains three areas. The first area is a description relative to the demographic concern (i.e. what you are trying to find, and why it's important). The second area is a Calculation Fields area that has two combo boxes within. One box is for the Numerator, and the other box is for the Denominator. Each combo box shows all field names from the newly created feature layer less the 'FID' and 'SHAPE' fields. The third area is the Field Names area. This area has two text boxes, one to show the new percent field name, and one to show the new vulnerability index field name. Once the numerator is selected from the Calculation Fields area, the Field Name text boxes are automatically set with new values that correspond to the names of the new fields that will be created in the table. As these two text boxes are not editable, this area is simply for you to see the new field names that will be added. For our purposes, if the Numerator name matches an attribute name we specified for the US Census file we create, the new field name gets preset to a value based on the naming convention we used before this tool was developed, otherwise, the new field name is the first 6 characters of the numerator field and then either preceded by 'PCT_' for the percent field name, or trailed by '_RSK' for the vulnerability index field name.

At the bottom of the form are three buttons: Next, Back, and Cancel. If you click the Next button, the application verifies that each tab has both the numerator and denominator fields selected before continuing. If all is well, the two fields noted in the Field Names area are created in the table as well as an additional field titled 'TOT_RSK' that is placed at the end of the table. The percent value is calculated and stored in the table under the new percent field. You are then taken to Step Three. The Back button takes you back to Step One and also deletes any new layers from the map document and file directory. The Cancel button will close the tool and delete any new layers from the map document and the file directory.



CREATE NEW FIELD AND CALCULATE

Just below the tab area is a section that allows you to create a new field in the table and perform some type of calculation on that field. This section is available at any time during Step Two. In Step Two, you are only able to select one field from the table for either the Numerator or the Denominator. A new field should be created if there are two or more fields within the table that represent one concern. For example, if the table has three fields representing the population over the age of 65 such as AGE65_74, AGE75_84, and AGEGT_84, these three fields must be added together to have one field that represents the population over the age of 65. The new field name is typed into the available box and when the Calculate button is pressed, a calculator appears to allow for some calculations for this field. The new field will be available for selection as either a numerator or denominator.




In this step, you will set the vulnerability index associated with each feature's percentage value and will calculate the total vulnerability for each feature within the table. You decide how to distribute the percentage values and what score to assign to that distribution. Again, there is a tab for each demographic concern. Within each tab there are three areas. The first is the classification area. This area contains two combo boxes. One allows you to select the classification method, which restructures how the sample data is displayed. The other combo box allows you to select the number of groups the percentage values will be broken into (class breaks:1-32). The second area is a grid showing class Range and Vulnerability Index. The Range shows the range of values that will be assigned the Vulnerability Index set by you. The third area allows you to choose to have a layer file created in the map that will show the symbology based on the vulnerability index for this particular concern only.

For example, if you were interested in a Low/ Medium/ Medium-High/ High range, 4 separate classes would be required. Select '4' from the Classes combo box. The grid then displays the range of values that fall within these four classes (see graphic below). A vulnerability index of 1,2,3,4, respectively, are automatically created for you when the class number is selected. You can then manually adjust the upper range values and the Vulnerability Index values to fit your specific needs.

In the area just below the tabs, there is another area that asks if you would like to classify the combined vulnerability index for all concerns. Checking this box will open the last step, Step Four.

At the bottom of the screen are the same buttons as on Step Two. The Cancel button performs the same function as in Step Two. The Previous button does not delete the new feature layer, but only hides the current form and opens Step Two. When the Next button is clicked, the tool then runs through the table and assigns the vulnerability index using the Range and Vulnerability Index values from the grid. (Ex. from below: for the InPoverty assessment, a percentage value of 11 would be assigned a vulnerability index of 2). Once all the vulnerability indices have been set, the tool then sums the vulnerability indices for each feature within the table to get a total vulnerability index for each feature. This value is saved in a field titled 'TOT_RSK'.






This step uses the 'TOT_RSK' field from the table since we are looking at the distribution of the total vulnerability values for all features. Again there are two areas. First is the Classification area where you select the classification Method and number of Classes. Second is the grid area that shows the class Range and Label values. These values are automatically set when either the Method or Classes parameter is changed, however, they can be manually adjusted as well. The Label value can be changed to express a more meaningful title, such as in the picture below. The Label value will be used to define the Range when the new layers symbology is set.

The Previous button will take you back to Step Three. The Finish button will create a new layer showing the symbology ranges based on the class ranges described in this step. The Cancel button will delete all new feature layers and layers from the map document and file directory.






In Step One, there is a box titled, Additional Concerns. Clicking this box opens another user input item where you select how many additional concerns (1-20) that you need to create. This allows for a more dynamic assessment outside of the set demographic concerns that have already been listed. This functionality can be used for any type of assessment that includes calculating a percent and then setting some vulnerability index based on that percentage value.

The form below allows you to select your Numerator and Denominator just as in Step Two. When this first form open depends on how the assessment tool is used. If you are using some of the predefined demographic assessments, then the first form will be available once you complete Step Two. If you are not using any of the predefined demographics, then the form below with open when you click next from Step One. This form offers the same functionality as in Step Two, however on this form, you have the added flexibility of changing the new field names that will be created. At the top of the yellow boxed information area is the number of the additional concern.




The next form allows for the same functionality as Step Three, only this form is used for the additional concerns. At the top of the yellow boxed information area, the number of the concern will be displayed along with the Percent field name that was created in the form above. This will allow you to keep track of which concern you are working on.