Nowadays, most regions don’t have a smart drainage monitoring system, or they manually track the condition of the drainage system. This causes abnormal drainage monitoring conditions, leading to blockages and flooding. The traditional way is to assign workers to go inside a drain. It requires a lot of manpower, and workers’ health may be affected as hazardous gases might be inside the drainage. This study emphasizes the usability and layout features of a smart, current-time drainage and manhole monitoring system that takes advantage of the Internet of Things (IoT). The manhole within the drainage may contain a module equipped with a microcontroller integrated with gas sensors (MQ2, MQ135), an ultrasonic sensor (HC-SR04), and a water flow rate sensor (YF-S201). Based on a predetermined threshold value of 7 cm, the system measures the water level and flow rates in drains and provides an alert if any blockage is found. It also detects dangerous gases and sends out alerts when the MQ135 and MQ2 sensors surpass 350 ppm, respectively. Using ThingSpeak for graphical visualization and Google Sheets for database administration, the system sends data to a central control center. All of these things will be made visible in real time by this system, allowing us to act appropriately at the appropriate time.