## 2 Materials and Methods
### Data Collection and Identification of Factors
#### 2.2.1 Flood Hazard Parameters  
Flood management cannot be adequately completed without assessing flood hazards [48]; therefore, details of indicators are elaborated below.  
1. Average Annual Rainfall  
Precipitation values were plotted on a suitable base map at their respective stations using isohyetal method, and isohyets were drawn to create an isohyetal map. The study used the climatological normal records [50] from long-term averages over 30 years of PAGASA weather stations (Figure 2) with corresponding coordinates. Spatial interpolation employing the isohyetal method was applied to obtain dimensional rainfall patterns for projections of Romblon.  
2. Slope  
The slope is a critical factor contributing to the intensity of destructive forces of floods in a particular area. The study prepared the slope map using the IfSAR DTM from National Mapping and Resource Information Authority (NAMRIA) and the spatial tool in the GIS application platform.  
\begin{table}
\begin{tabular}{l l c c c} \hline \hline
**References** & **Parameter** & **Data Type** & **Duration/Year** & **Source** \\ \hline
[46; 47; 48] & Water Usage & Primary source of water & 2022 & Survey Questionnaire \\  & Emergency Preparedness & Emergency preparedness during unexpected & 2022 & Survey Questionnaire \\  & Types of Built-up & \
\begin{tabular}{c} Classification of structures of \\ every household \\ \end{tabular} & 2020 &
[29] & Types of Built-up & \begin{tabular}{c} Classification of structures of \\ every household \\ \end{tabular} & 2020 & \begin{tabular}{c} Barangay Profile \\ Site Investigation and \\ Survey Questionnaire \\ \end{tabular} \\  & Distance from the nearest & \
\begin{tabular}{c} Distance of identified evacuation area using \\ buffer tool in Arcmap \\ \end{tabular} & 2022 &
\begin{tabular}{c} Site Investigation and \\ Survey Questionnaire \\ \end{tabular} \\ \hline \hline
**Flood Exposure Parameters** & & & & \\ \hline
[9; 29; 40; 42; 49] & Population Density & \
\begin{tabular}{c} Computed from the population over the \\ covered area of the barangay \\ \end{tabular} & 2020 &
\begin{tabular}{c} PSA \\ PSA \\ \end{tabular} \\
[43] & Household Number & Number of households of every barangay & 2020 &
\begin{tabular}{c} Municipality of Odiongan, \\ Romblon—(CLUP) \\ \end{tabular} \\
[6; 17; 26; 35; 40; 41] & Land Use/Land Cover & Land cover map from CLUP & 2011 &
\begin{tabular}{c} **PAGASA** \\ **Weather Stations** \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}
Table 1: _Cont._  
Figure 2: Weather stations considered in the interpolation for average annual rainfall using the Isohyetal Method.  
Elevation  
Ground elevation is one of the main factors that should be considered in assessing flood hazards. IfSAR data were utilized and processed in the GIS tool.  
Soil Type  
The study used the soil map based on the map of NAMRIA stipulated in the Comprehensive Land Use Plan (CLUP) [51] of the Municipality of Odiongan. These data were correlated to the soil's water holding capacity and infiltration rate.  
Flood Depth  
ArcGIS, HEC-HMS (Hydroologic Engineering Center's--Hydroologic Modeling System) [52] and HEC-RAS (Hydroologic Engineering Center's--River Analysis System) [53] were the tools used for flood hazard simulation. The most important data used in the simulation were the DEM, which were provided by NAMRIA with a resolution of five-by-five (5 \(\times\) 5) meters. A combination of simulated maps and Flood Susceptibility Maps [54] from the Mines and Geoscience Bureau (MGB) were used in the study.