The middle stream and upstream of main rivers in western Taiwan exists serious subsidence situation. The changes in the real-time water level and scour depth during flood and typhoon seasons influence the safety of bridges significantly. Bridge management unit often use water level elevation as a bridge closure decision basis. Although simple

but this is lack of a strong technical support. Therefore

scour depth monitoring system capable of functioning in the floods impact is very important. Among existing automatic observation methods for scour

the instruments and equipments are limited to the river course silting form

high sand content

high salinity

difficult device installation and conflict between onsite laying and construction. They may not reflect local scour behavior of submerged bridge foundation in a timely manner. Therefore

this study cited the Sutong Bridge scour monitoring technology

through the sunk piezometer under riverbed and water level real-time measurement to comparison of the head difference to find the scour depth. However

the Sutong Bridge is a sandy riverbed. In this study

the bridge is a gravel riverbed. Due to the long and narrow terrain of Taiwan

the river is steep and fast. For the construction and preservation of monitoring equipment is more difficult to measure than the Sutong Bridge. This study has considered the safety monitoring of civil engineering suitable for the harsh environment. The use of a sturdy and sealed steel hoop helped the piezometer not only maintain a high degree of reliability and stability in the long-term monitoring process

but also can be operation in the harsh environment.