Siti Nazahiyah Rahmat

Analysis the Impact of Bridges Existance for the Segamat River Using Infowork RS

Malaysia is experiencing two monsoonal seasons, which have induced heavy rainfall. The increasing of rainfall intensity and longer duration of rainfall has caused a flood. In 2007, Segamat city was hit by the flood due to increasing of rainfall and this has caused a huge damage in term of infrastructure as well as human life. Thus, this study was carried out with the aims to analyze the flood and develop a flood map for the Segamat River. The hydrological data, such as rainfall and streamflow data were retrieved from the Department of Irrigation and Drainage Malaysia (DID). While, for map preparation such as base map, landuse map and river map were delineated based on the topography map. Additionally, contour map was obtained from MACGDI. InfoWork River Simulation (RS) software was used for analysis and develops the flood map. Moreover, two scenarios were carried out to determine the effect of hydraulic structure presence in the waterway. The first scenario is the flood map without a bridge, while the second scenario is the flood map with a bridge. Based on the results, it clearly shows that the flood map with a bridge has higher flow, velocity and water table compared to the flood map without a bridge. In addition, a flood-prone area based on the developed map was identified. Thus, the generated flood map could serve important information to related agency in proposing a suitable design the mitigation works for this area.

Temporal Trends of Discrete Extreme Events - A Case Study

Investigating trends in discrete events is essential for the study of changing patterns of extreme events. Temporal trends in the inter-arrival times of occurrence of drought events were examined for 21 selected stations across Victoria, Australia. In the present study, the Standardize Precipitation Index (SPI) was applied for 12-month time scale to identify drought. A drought event here is defined as a period in which the SPI is continuously negative and reaching a value of -1.0 or less. Often, nonparametric tests are commonly used to test for trends including in discrete events. However, discrete events are not constant because of the presence of zero values or non-normality of data. The methodology applies to long-term records of event counts and is based on the stochastic concepts of Poisson process and standard linear regression. Overall, of the 21 stations, 15 showed statistically significant increasing frequency indicates those events are becoming more frequent. Only one station gave insignificant result. The remaining 5 stations showed the time between events was significantly increasing designates droughts are becoming less frequent.

Development of drought severity-duration-frequency curves in Victoria, Australia

Abstract One of the many ways in preparing for drought is to carry out a drought risk assessment by characterisation of the frequency, severity and duration of a drought. Therefore, the current study aimed at the development of severity-duration-frequency (SDF) curves to provide a comprehensive characterisation of the droughts for 10 selected stations in Victoria, Australia. The development of the frequency curves is based on the precipitation deficits which were computed based on the Standardised Precipitation Index (SPI). Instead of using SPI values, the precipitation thresholds were used to compute the severity of the droughts. This would be very helpful in delivering information that can be understood easily by ordinary users and decision-makers. The SDF curves were developed using the partial duration series (PDS) technique. Log Pearson Type III distribution was chosen and fitted well to the precipitation deficits for different durations of drought. Overall, SDF curves were successfully derived for 10 stations in Victoria and can provide useful information for medium/long term planning, such as in planning irrigation supply and developing drought relief policies.