# A Review of Cutting-Edge Sensor Technologies for Improved Flood Monitoring and Damage Assessment
## 3 Overview of Flood Sensor Development
### Flood In Situ Sensors  
Establishing early warning systems using sensor devices to send alerts via SMS or the Internet is an effective method for reducing flood risk. Different kinds of in situ sensors are used in the early stages of flooding (Table 2). Figure 4: Summary of early monitoring sensors for various types of floods. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sensor** & **Index** & **Advantages** & **Disadvantages** \\ \hline \multirow{4}{*}{Pressure Sensors} & & 1. High-precision & 1. Requires regular calibration \\  & & 2. Real-time & 2. Stable power supply is required \\  & water level, water pressure & 3. Deep water and submarine environment & 3. Restricted installation locations \\  & & 4. Anti-interference & 4. Subject to environmental \\ \hline \multirow{4}{*}{Electromagnetic Sensors} & & 1. Non-contact measurement & \\  & water level, flow rate, velocity & 2. High accuracy & 1. High costs \\  & water level, flow rate, velocity & 3. Suitable for different media & 2. Need for a stable power supply \\ \hline \multirow{4}{*}{Capacitive Sensors} & rainfall, humidity, barometric & \\  & pressure, soil moisture, water & 1. High-precision & 1. Periodic calibration required \\  & level, water quality, & 2. Suitable for different media & 2. Subject to environmental \\  & displacement, depth of & 3. Anti-interference & influences \\ \hline \multirow{4}{*}{Resistive Sensors} & humidity, soil moisture, water & \\  & level, water quality, & \\  & displacement, barometric & 1. Simple structure & 1. Lower accuracy \\  & pressure, depth of & 2. Economical & 2. Easy to be corroded \\  & standing water & & \\ \hline \multirow{4}{*}{Fiber Optic Sensors} & temperature, water level, & 1. Compact structure & \\  & water quality & 2. High flexibility & 1. High costs \\  & water quality & 3. Remote monitoring & 2. Complex installation and \\  & water quality & 4. Anti-electromagnetic & maintenance techniques \\ \hline \multirow{4}{*}{Ultrasonic Sensors} & wind speed, wind direction, & 1. Non-contact measurement & \\  & water level, flow rate, flow velocity, wave height & 2. High-precision & 1. High costs \\  & water level, flow rate, flow & 3. Fast response time & 2. Easily damaged \\  & velocity, wave height & 4. Unaffected by the & 3. Affected by temperature/noise \\  & & environment & 4. Limited sensing distance \\ \hline \multirow{4}{*}{Infrared Sensors} & & 1. Non-contact measurement & \\  & temperature, water level, & 2. Fast response time & 2. Affected by the surface \\  & water quality, wave height & 3. Economical & properties of objects \\  & water quality, wave height & 4. Particularly suitable for flat & 3. Higher accuracy within a \\  & & and smooth water surfaces & certain spatial range \\ \hline \multirow{4}{*}{Acoustic Sensors} & rainfall, rain sound, & 1. Detectable underwater & \\  & underground sound, water levels, underwater velocity, & conditions & 1. Affected by the quality of water \\  & underwater topography, & 2. Adaptable to harsh & 2. Complicated data processing environments \\  & underwater objects & \\ \hline \multirow{4}{*}{Wave Sensors} & water level, flow velocity, flow & 1. Real-time & 1. Affected by temperature/noise \\  & direction, underwater objects, & 2. Remote within a & 2. High costs \\  & ground vibration & certain range & 3. Complicated data processing \\ \hline \multirow{4}{*}{Float Sensors} & water levels, flow & 1. Simple and reliable & 1. Low-precision \\  & velocity, fluctuations & 2. Economical & 2. Easily damaged \\  & & 3. Easy to install and maintain & 4. Not suitable for high-pressure \\ \hline \multirow{4}{*}{Buoy Sensors} & water levels, water quality, & \\  & flow velocity, & 1. Highly mobile & 1. High costs \\  & waves, flood extent & 2. Adaptable & 2. Low positioning accuracy \\ \hline \multirow{4}{*}{Line Sensors} & water levels, flow velocity & 1. Economical & 1. Easily damaged \\  & water quality, & 2. Equitable for confined spaces & 2. Restricted mounting position \\ \hline \hline \end{tabular}
\end{table}