This document proposes a smart underground drainage blockage monitoring and detection system using IoT. It discusses how current manual drainage monitoring is inefficient and poses risks. The proposed system uses ultrasonic sensors and gas sensors connected to an Arduino board to remotely monitor water levels, detect blockages, and measure harmful gas levels in underground drainage lines. If sensor readings exceed thresholds, the system alerts authorities by SMS with the location of the issue so it can be addressed quickly. This smart system aims to improve drainage management and public safety in cities compared to traditional manual methods.