# Presentation: 906041

## Using HAZUS-MH to Assess Tsunami Risk

**Using HAZUS-MH to Assess Tsunami Risk**

- Bill Bohn, Tetra Tech
- June 19, 2007

## How Can the Current Model be Used to Assess Tsunami Risk?

- Earthquake, flood, and hurricane wind loss estimates are currently produced.
- Inundation maps used with HAZUS-MH inventory data may be used to show what is at risk.
- HAZUS-MH damage functions may be edited.

## Northern California Case Study

- Profiling the tsunami hazard
- Modeling the inundated area
- Calculating the exposure
- Using the Flood Wizard software
- Editing the HAZUS-MH Software

## Tsunami Profile

- 82 tsunamis have been observed or recorded in California since 1855.
- 11 caused damage to the infrastructure
- 4 caused casualties
- Area at risk from both distant and local tsunamis (Cascadia Subduction Zone).
- Experts estimate a 35% probability of a large (8+ magnitude) Cascadia earthquake occurring from 1995 to 2045.

## Modeling the Tsunami

- Tsunami model developed by Humboldt State University
- Tsunami caused by Cascadia earthquake (little to no evacuation time)

## Exposure

- Determining which site specific buildings are in the inundated areas
- Calculating the general building stock within the inundated areas

## Inundation Results

- 100-year tsunami exposure – general building stock
- 100-year tsunami exposure – critical facilities

## Using the Flood Wizard

- Create flood region in HAZUS-MH
- Download Digital       Elevation Model (DEM)
- Convert inundation area to shape file with a field named “Zone” and containing an “A” in each record

## Editing the Damage Functions

## Tsunami Sources

- FEMA Coastal Construction Manual, 3rd Edition
- ASCE 7-02 Minimum design loads for buildings and other structures, 2003
- City and County of Honolulu Building Code, 2000
- Matsutomi, Tsunami Engineering, 1999
- Harry Yeh, Oregon State University

## Damage Function Components

- Breaking wave forces
- Hydrostatic forces
- Buoyant forces
- Hydrodynamic forces
- Surge forces
- Impact forces

## Breaking Wave Forces

- Wave breaking typically takes place offshore.
- Exception occurs with a steep slope beach.
- Beach elevation data was analyzed and these forces were removed from consideration.

## Hydrostatic Forces

- Important for 2-D structures such as seawalls.
- Fhs = pcAw = ρg(h – hw/2)bhw
- pc is the hydrostatic pressure at the centroid of the wetted portion of the wall
- Aw is the wetted area of the wall
- hw is the height of the wall panel
- h is the height of the water

## Buoyant Forces

- Buoyant forces act vertically through the center of mass of the displaced volume.
- A concern for wood frame buildings.
- Fb = ρgV

## Hydrodynamic Forces

- Occurs when steady water flows around a building.
- Fhd = 1/2CdρAfu2 α bhu2, where u is velocity and                                                b is breadth

## Surge Forces

- Caused by the leading edge of a surge of water.
- Fs = 4.5ρgh2b

## Impact Forces

- Caused by debris impacting the structures.
- Used HAZUS inventory to help determine debris type.

## Flood Wizard Results

- 100-year tsunami losses – general building stock

## Editing the HAZUS-MH Software

- Create a coastal flood region
- Enter the tsunami inundation elevations as the 100-year still water elevations (SWEL).
- Replace the default damage functions with the tsunami damage functions.
- Run the 100-year coastal flood.

## Conclusions and Next Steps

- Although HAZUS-MH does not produce loss estimates for tsunamis, the model may be used to help evaluate the risk.
- Next steps:
- Run the HAZUS-MH model with the new damage functions.
- Validate the results.

## Questions?

- Bill Bohn
- Phone: 703-390-0712
- Bill.Bohn@ttemi.com