Effective risk management for flash flood disasters is now achievable, thanks to 21st century technological advances in communication technology, spatial data analysis, and weather prediction.
The Asia and Pacific region is battling a number of devastating flash flood disasters both in urban and rural settings. The People’s Republic of China, India, Indonesia, Mongolia, and Nepal are among the countries affected by recent floods that have caught public attention.
While rainfall is a key trigger, there are many other factors that contribute to flash floods. These include land use, given that a large number of urban areas are being developed every year on low-lying, flood-prone land. In the face of this, affordability and cost-effectiveness of flash flood risk management measures are vital.
Relatively low-cost approaches – compared to structural measures such as dikes and dams –include flash flood forecasting and early warning systems.
For flash floods, there is only a short time available for warning, preparation and response. Flash flood forecasting and early warning systems require denser hydro-meteorological monitoring networks and real-time data acquisition and transmission. Recent technological advances in information and communications, remote sensing, and weather forecasting enable more effective, more accurate and more efficient forecasting and early warning.
However, these technologies are yet to be effectively incorporated in the development planning of governments in the Asia and Pacific region.
Some of the technical tools useful in flash flood forecasting and early warning are not new. For example, hydrological models that forecast timing and magnitude of flood peaks or delineate areas of inundation, as well as data acquisition networks, have all been around for many decades. Their application in risk management of flash floods has been enhanced by advances in communication technology, spatial data analysis, and weather prediction.
Linking flood forecasting with short-term weather forecasting would be of considerable benefit as it would allow more time for emergency preparation and response. This process is made possible by ground-based weather radar, which can accurately determine rainfall amounts before it falls on the ground within a more than 100 kilometers radial distance.
The installation, operation, and maintenance costs of weather radar are relatively high compared to ground observation stations, but are worth the investment because of their precision and their aerial coverage. However, the level of expertise required to make use of radar data in flash flood forecasting and early warning systems is yet to be developed in many countries.
Numerical weather prediction models simulate the complex climatology of the atmosphere, analyze satellite remote sensing data, and can utilise a host of observations to make short-term quantitative precipitation forecasts. The accuracy and spatial resolution of these forecasts continues to improve as remote sensing technology advances.
Only a few decades ago, effective flood risk management was more a wish than a realistic prospect, but times have changed.
Cloud computing can serve as a platform for data analysis, modeling, information sharing, and forecast display in a near-real time basis without much dependency on human inputs. Long-range wireless technology, initially developed for the Internet of Things, can be applied as local data transmission networks.
New multi-function semi-automated terminals can also be used by local institutions and communities, provided with a new type of communication channel featuring an automatic alarm.
Artificial intelligence technology can be applied for text-voice conversion of warning messages. This would enable the flash flood early warning system to function as an almost fully-automated system, which is consistent and easy to understand and follow by a targeted population. Mobile phone apps can allow residents and officials to interrogate sources of data and emergency advice.
The global positioning system can identify the locations of all active mobile phones within flood risk zones and can be coupled with a geographic information system to guide a rescue operation, similar to using a common navigation program.
To make flood early warning systems effective, raising public awareness of flood risk should be prioritized in areas susceptible to flash flooding, and in regions with low incidence of serious flooding. Particularly, cooperation between upstream and downstream communities in information sharing and emergency response is of utmost importance.
This can be done more efficiently given advances in technologies. But local governments need higher capacity to operate such flash flood forecasting and early warning systems. This includes capacity in hydrological and hydraulic modeling, which can generate flood forecasts and delineate the flood risk zones. Effective end-to-end early warning systems utilise the flood risk maps, enabling land use and demography to inform the contingency plan.
A regional or national approach to implementing flash flood forecasting and early warning is preferable. However, in many countries, resource constraints may make a systematic approach impractical and flash flood forecasting and early warning systems is not yet incorporated in development planning.
Often, flash flood forecasting and early warning is blended with national flood or weather forecasting systems, which may not be as effective. On the other hand, the capacity of local governments and communities to manage flash flood forecasting and early warning systems is generally very weak in the region.
Flash flood forecasting and early warning not only saves lives, it relieves rural poverty by breaking a vicious cycle of disaster and recovery. The residents of remote villages and farming families in mountain valleys, mostly elderly, differently abled, women and children, are particularly vulnerable to this recurring cycle of poverty and misery.
Resources are limited for post-disaster recovery. The frequency and severity of flash floods are also increasing because of global warming, so flash flood forecasting and early warning also has an important role to play in climate change adaptation.
Only a few decades ago, effective flood risk management was more a wish than a realistic prospect, but times have changed. Recent technological advances now make it possible, given adequate initiative and resources.
Future technological improvements will further enhance flash flood forecasting and early warning systems – bringing them well within the reach of any affected community, improving accuracy and reliability, reducing flood damage, and saving more lives.