Hazard Analysis

Scenario Hazard Analysis Basis:

The scenario cyclone-hazard estimates peak gust wind intensity at sites using a wind field model that includes surface pressure field and a system translated speed (Vickery and Wadhera 2008). The wind field model estimates the spatial variation of the wind speed over a large study area (Salman and Li 2018).

Holland (1980)’s wind field model used to estimate wind speeds of a cyclone. The appropriate scenario event for a particular region can be selected based on the frequency of hazard occurrence and the community’s risk perspective. The HURDAT2 database is a good source that used in this study to obtain recorded past cyclone tracks chracteristics (i.e., location, time of occurrence, maximum wind speed, landfall location, storm category, central pressure). The strongest cyclone wind occurs at the eye wall, and wind intensity decays as the location moves away from the cyclone center (Xu and Brown 2008). Gradient wind speed at building location is estimated using the radial wind profile model provided by Holland (1980)

Scenario Hazard Analysis Inputs:

This module requires (1) cyclone input track, and (2) targeted structural inventory (i.e., buildings) location to estimate gust wind speed at structural inventory sites. Following table shows input characteristics of cyclone input track and buildings.

Table 1 cyclone input track.

Column Title	Description
sl	Row number
Time	Time of cyclone (time step - i)
Lat	Latitute of cyclone eye
Long	Longitude of cyclone eye
CP	Central Pressure Difference

Table 2 building input data.

Column Title	Description
id	Building unique identifier
Lat	Latitute of building
Long	Longitude of building
Floor	No of storey
Area	Area of the building
type	Structural archetype
Occupancy	Building use

Running Hazard Analysis:

1. CycloneParameters: this model computes cyclone hazard

2. estimate_parameters: this function estimates parameters for input track

3. calculate_wind_speeds: this function estimates wind speed at sites

Following is an example of running hazard module to estimate the cyclone parameters and intensity at buildings:

# track_df: cyclone track input dataframe (see table - cyclone input track), df_track: estimated hazard parameters,
# and blg: buildings inventory (see table - building input data), df_bdg_wind: estimated wind speed, VG: gradient wind speed (kmh).
cyclone_parameters = CycloneParameters(track_df)
df_track = cyclone_parameters.estimate_parameters()
df_bdg_wind, VG = cyclone_parameters.calculate_wind_speeds(df_track, blg)

This module provides wind speed for buildings/structures. Adds wind speed ‘mph/kmh’ to building/structure inventory, which is used for vulnerability analysis.