Design of a flood detection system using functions to monitor water level heights and can be controlled by a smartphone with the blynk application. This tool is designed using ESP32 as a Wi-Fi module, a water level sensor to determine the water discharge level and a relay to function as a switch. The way this tool works is to detect the arrival of floods through a level sensor and the data is directed to the ESP32 microcontroller as a medium and sent by the output indicator lights, LCD displays and smartphones in the blynk application called flood monitoring. The test results use a water level sensor with a variation of 3 levels, namely level 1, level 2, and level 3. The indicator light uses 3 colours, namely green, yellow, and red. The measurement results on the power supply by a multimeter obtained a value of 8.97 V and the calculation results obtained a value of 8.10 V so the difference of 0.87 V is still a reasonable tolerance.If the sensor reaches level 3 it will send a notification in the form of a notification to blynk so that the red indicator light will turn on, and the pump will automatically turn on. The flood detection and control system operates well after a trial of flood monitoring and control through the blynk application.