28 April 2010

Real-time flood forecasting and monitoring system

By Kuok King Kuok

(Published in’Campus & Beyond’, a weekly column written by Swinburne academics in the Borneo Post newspaper)

The most severe natural disasters in Malaysia are monsoonal floods and flash floods. Due to its geographical location, Malaysia is directly influenced by the Asian Monsoon. The country receives abundant rainfall mainly from the Southwest and Northeast Monsoons. The Southwest Monsoon, which prevails during the later half of May or early June to September, brings less intense rainfall. However, blowing from November to March, the presence of the Northeast Monsoon is indicated by heavy rain over most of the main cities and towns in Sarawak including its capital city of Kuching, as well as Sibu, Miri and Bintulu.

The annual rainfall in Sarawak is estimated to be around 4,000 mm. This causes monsoonal and flash floods. For the past 10 years, the major towns in the State have experienced severe flooding in 2003, 2004 and 2009. Sibu alone was flooded eight times in 2009. Therefore, there is a need to provide relevant and accurate data in weather forecast and monitor water levels in rivers.

196719In Sarawak, flood monitoring is the responsibility of the Department of Irrigation and Drainage Sarawak (DID) and Sarawak River Board (SRB). DID monitors Sungai Sarawak, the Lower Rajang, Upper Rajang Basin, Oya, Mukah, Balingian and Baram Basins. SRB has a complete telemetry system in Sungai Sarawak Basin for Kuching Barrage operation near Sejingkat.

The flood monitoring and early warning system is a real-time computer system that utilizes state-of-the-art technology in remote telemetry. The schematic diagram of telemetry system is shown in Figure 1. The flow of the system starts with the Remote Terminal Unit (RTU), which collects rainfall and/or river water level and/or other hydrological data from the interfaced sensor. The collected data is stored in the data logger unit and will be transferred or transmitted to the Master Control Center (MCC) through various communication systems. The MCC provides real-time hydrological information together with alert, warning and danger level (for water level stations).

There are several types of communication systems that perform data acquisition, collection and flood monitoring. The communication technology widely used for data transmission are VHF Radio, Low Earth Orbit (LEO) Satellite including Inmarsat Satellite services type A, B, C, D+, E, M, mini M, GAN, R-BGAN and Digi/Maxis/Celcom/GPRS network connectivity.

VHF radio transmission is most suitable and reliable for RTUs located within 100km from the MCC. GPRS and GSM technology is employed if the RTU is within the coverage of Digi/Maxis/Celcom/GPRS. In the event that the location of the RTU is not covered by Digi/Maxis/Celcom/GPRS and is located more than 100km from the MCC, the data will be transmitted via LEO satellite services.

Fig.1 : Schematic Diagram of Telemetry System

Cameras that use Digi/Maxis/Celcom/GPRS or internet services for security and flood monitoring purposes are installed at the stations. These cameras capture images at various angles and have night vision capability for viewing in the dark.

The cameras may also be used to view the water level for flood monitoring purpose.

For the telemetry system operated by DID in Malaysia, the MCC in each state replicates the data with the National Data Fusion System Center (Infobanjir) over a secure internet connection to synchronize data between states across the country. These synchronized data are then published on the Infobanjir (http://infobanjir.water.gov.my) web portal.
The website provides information including rainfall data, water level data, shots of online camera picture, and also database of rainfall and water level – all in real time. The online rainfall and water level data displayed are useful indicators of potential flooding or landslides.

However, the telemetry system will be more advanced and utilized fully if it is able forecast water levels. These days, there are hundreds of flood forecasting models available but the model to be used must be accurate, reliable, less assumption-dependent, simple, efficient, robust and flexible, and uses only rainfall and water level data. This is because most of the hydrological data gauged in Sarawak are rainfall and water level only. The two types of real-time flood forecasting models that proposed using only rainfall and water level data are Artificial Neural Networks and the Sugawara Hydrological Tank models.

In carrying out flood forecasting routines, real-time rainfall and water level data are obtained from the telemetric network. These data are processed, checked and used in the computer-based flood forecasting model. These forecast water level data are important especially during the wet season. Such improved flood forecasting and warning system could reduce loss of lives and damage to property.

With advancement of ICT in the 21st century especially in the application of real-time flood forecasting and monitoring system, it is hoped that the public will have first-hand and instantaneous information so that flood mitigation and management can be carried out efficiently and effectively.

Meanwhile, real-time monitoring system can also be used to track the level of water in rivers during droughts, keep tabs on reservoirs and monitor irrigation canals as is practised by Muda Irrigation Scheme, or MADA.

Kuok King Kuok is a lecturer with the School of Engineering, Computing and Science at Swinburne University of Technology Sarawak Campus. He can be contacted at kkuok@swinburne.edu.my.