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As part of the water cycle, groundwater is a major contributor to flow in rivers and has a strong influence on landslide. This paper proposes a landslide early warning system for detecting landslide. Our aim is to analyze the groundwater flow by conducting laboratory test in Politeknik Negeri Semarang, Semarang City on groundwater flow detectors' sensors accuracy on rainfall, water level and soil moisture content. We undertook this research by employing LoRa and testing the performance of sensors on groundwater flow using a rainfall sensor, a soil moisture content detector using a capacitive soil moisture sensor, and the water level detector using the VL53l0X sensor and tested using a permeability tank. We used Muntilan sand which is categorized as well-graded sand in our experiment. The results of rainfall sensor test resulted in an effluent value of 0.053 inch or 1.346 mm of water, while the water level sensor produced an average error of 0.02667 for object distance testing, and for soil moisture sensors in dry sand, it produced ADC 2.94 V while wet sand results in 2.084 V. We conclude that the accuracy of rainfall and water level are good, while for soil moisture content is bad due to sensor's sensitivity since the operating voltage is 3.3 ~ 5.5 VDC. [ABSTRACT FROM AUTHOR]

Rainfall especially in tropical region caused infiltration to the soil slope. The infiltration may change pore water pressure or matric suction of the soil. The event of rainfall infiltration into soil is a complex mechanism. Therefore, the main objectives of this research paper is to study the influence of rainfall intensity and duration that changed pore water pressure to soil. There are two types of soils used in this study; forest soil and kaolin. Soil column apparatus is used for experiments. Rainfall were applied to the soil and result for 3, 6, 12, 24, 72, 120 and 168 hours were retrieved. Result shows that for the both types of soil, the negative pore water pressures were increased during wetting process and gradually decreased towards drying process. The results also show that pore water pressure at top part was increased greatly as the wetting process started compared to the middle and bottom part of the column. [ABSTRACT FROM AUTHOR]