Since time out of mind, floods, mainly caused by rain storms, melting snow or long-term rainy weather, have represented a serious hazard to the both property and human lives in some regions. The level of preciseness, with which meteorologists forecast such events, is reasonably high nowadays despite the fact that it is quite difficult to forecast intensive local rainfall. It requires expensive technical equipment designed to monitor weather conditions, especially its cloudiness, and systems designed to monitor water levels of various, otherwise inconspicuous, creeks and potential waterways. Since storm water can represent very sudden danger, it is necessary to warn people in danger very fast and in an efficient manner.

This solution integrates a warning and notification system with a monitoring system or several monitoring systems. The warning and notification part of the system is used to warn and notify people in danger in several stages based on information from a monitoring system. In order to acquire potential hazard data various procedures are used depending on whether such floods were caused by long-term rainy weather and raised river levels or by rain storms and their subsequent sudden floods. Computer simulations are nowadays able to specify area points of higher probability of danger. Monitoring systems provide information in two basic ways:

• They forecast flood conditions on the basis of information obtained from special meteorological stations;
• They inform on actual water levels in rivers, creeks or in points, down which rain storm water usually flows;

This solution of a flood early-warning system can work with information from meteorological stations and from existing monitoring systems. It can also use its own system for water level monitoring. The main communication channel of its monitoring system and of a warning system is a radio channel and it is shared by both of the systems, thus reducing costs of their establishment. To create a short-distance connection of sensors and the main communication channel ZigBee radio technology is used. The system consists of:

• An evaluation and warning centre, which can be fully automated;
• Communication infrastructure;
• Level sensors;
• PAVIAN electronic sirens, and, potentially,AMADEO line broadcasting system or TIBOR cordless broadcasting system;

Evaluation and warning centre
This consist of a computer equipped with VEKTRA software, of a central communication unit for siren radio control and for gathering data from sensors and of other notification hardware. The VEKTRA software evaluates data from level sensors and meteorological stations. It further checks conditions of individual sirens and communication channels, activates these sirens and notifies people and institutions in the case of a danger. The workplace can be automated and controlled remotely from a mobile phone, a PDA device or a radio station. Depending on the assumed progress of a danger it is possible to configure several system reaction scenarios. A scenario can cover notification of people in charge as soon as first symptoms of potential flood event occur, e.g. via phone, preliminary announcement to the people in danger via sirens or broadcasting systems, and actual emergency announcement in the case of an immediate danger.

Communication infrastructure and water-level sensors
A designated radio channel is used as a main communication channel. It is to control sirens and transmission of data from sensors. In some places, in which water level monitoring is required no power supply might be available. The sensors there are charged from batteries sending messages on water levels via Zig-Bee technology radio broadcasting. Batteries can keep charging sensors for several years. It is also possible to use sun collector-charged batteries.

PAVIAN electronic sirens, AMADEO AND TIBOR radio units
PAVIAN-type electronic sirens or AMADEO and TIBOR radio units can be used as a terminal acoustic feature. These are designed in such a manner that the entire populated area in danger would be covered with acoustic signal of a desired acoustic pressure. Considering extremely high requirements related to such system reliability, the entire functionality of this equipment is used, mainly the auto-testing one. Application of AMADEO or TIBOR broadcasting systems or connection to existing broadcasting systems can send acoustic messages, effectively and directly, to the people in danger, which is often very useful in terms of evacuation control.