Several nonstructural measures can be modeled in HEC-FDA. This page describes methods for modeling common nonstructural measures.

Structure Elevation

Structure elevation involves raising the structure so that a higher water surface elevation is required to damage the structure. Structure elevation shifts the stage-damage curve to the right:


When importing a structure inventory, the user is prompted to select an input method for first floor elevation. Damages accrue relative to the first floor elevation of a structure, so determining the value for first floor elevation is important. The user can select either First Floor Elevation, or Ground Surface + Foundation Height for the input method. 

First Floor Elevation = Ground Surface Elevation + Foundation Height

To model structure elevation, a separate structure inventory will need to be imported with changes to the foundation height or first floor elevation for the targeted structures. If the user opted for First Floor Elevation, this value will need to be increased in the with-elevations structure inventory. If the user opted for Ground Surface Elevation + Foundation Height, the Foundation Height value will need to be increased in the with-elevations structure inventory.

The image below shows a structure inventory for the nonstructural measures. Two columns are highlighted showing original foundation height (found_ht) and new foundation height (NewFndHt) which represents the raised foundation. The new foundation height is larger than the original, and this represents nonstructural elevation of structures.

The user will select the column for the new foundation height when importing the nonstructural structure inventory as shown below:

Floodproofing

Floodproofing involves preventing damage to a structure up to a certain depth, either by keeping water out of the structure (dry floodproofing) or allowing water to pass through the structure without causing damage (wet floodproofing). Floodproofing truncates the stage-damage curve:

The structure's occupancy type dictates percent damage for a given depth of flooding on the structure. The structure inventory has a column indicating the occupancy type, and the occupancy types contain the depth-percent damage functions. Typically, floodproofing is assumed to prevent damages up to three feet of depth, and then the structure will resume the normal depth-percent damage function for depths above that. 

To model floodproofing in HEC-FDA, new occupancy types will need to be created for any structures targeted for floodproofing and a new structure inventory will need to be imported with the targeted structures' new occupancy types. The new occupancy types should show zero percent damage for depths up to three feet.

Below is an example of an occupancy type for commercial structures. On the left is the regular depth-percent damage function, on the right is the depth-percent damage function with floodproofing in place.

Note that many structures may be assigned the COM occupancy type, and many of those structures may be targeted for floodproofing and use the COMFP occupancy type in the with-project condition. A new occupancy type does not necessarily need to be created for each individual structure.

Acquisition

Structure acquisition involves removing structures from the inventory. Acquisition can shift the stage-damage function downward.

When a structure is targeted for acquisition, that structure is no longer in the model in the with-project condition. Modeling structure acquisition is simple: remove or delete the structure from the inventory. A with-project condition structure inventory with the removed structures will need to be imported. Highlighted the targeted structures and select delete, such as shown below:

The with-project structure inventory is imported as normal.