Wireless Sensor Networks for Debris Flow Observation

Abstract

This work is to augment a debris flow observation and early warning system with wireless sensor networks. Previously, the GIS at Fengchia University has constructed and deployed state-of-the-art, stationary and mobile types of observation systems at nearly 20 sites throughout Taiwan. These sites collect data from sensors ranging from rain gauges and tension cables to ultrasonic sensors and CCD cameras, and transmit them back to the GIS via a lower-orbit satellite uplink in real-time. A new wireless sensor network and middleware system are being designed and implemented to overcome several limitations with the current system. Wireless communication capabilities are being incorporated to enhance the coverage. Previously, most connections between the sensors and the server before the satellite uplink are wired or Wi-Fi with fixed topology and limited range. New wireless interfaces with a 500 m - 1 km range plus energy harvesting devices on the sensors reduces deployment effort and cost. More importantly, it is now becoming possible to construct and deploy brand new types of mobile sensor nodes that move with the debris flow along its path. Such sensor nodes are to be housed in pyramid-shaped, weather-proof capsules that contain motion sensors, GPS and other localization devices, energy harvesting and storage devices, and wireless transceivers. Normally in low-power or standby mode, these capsules would be deployed in the path of potential debris flows. They would stand steadily during normal weather conditions including wind, rain, and water flow. They would get triggered by a threshold motion detector or a rain gauge and start actively monitoring the flow. As it flows with the debris, these capsules transmit their sensor data wirelessly, via other relaying nodes if necessary. Based on the shape and mass of the capsule itself and the velocity, researchers can derive the direction and magnitude of the flow in brand new ways.