High magnitude flash flood has occurred several times in some areas in Central Sulawesi Province after the 2018 Palu Earthquake, one of them is in the Bangga River, Sigi Regency, Indonesia. It has caused massive impacts such as damaging agricultural and plantation areas and submerging public facilities and infrastructure and even causing fatalities. The flood carries a variety of materials, especially high concentration sediments which are thought to originate from eroded soils due to landslides induced by a 7.5 magnitude earthquake. These materials are eroded and transported by the flow at the upstream watershed due to heavy rainfall. This study intends to investigate the potential of landslides, factors that trigger floods and increased flooding after the earthquake. This research was conducted by investigating the landslides potency based on field surveys and interpretation of the latest satellite imagery, analyzing the characteristics of rainfall as a trigger for flooding, and predicting the flood potency as the primary impact of these two factors. Rainfall-flood transformation was simulated with the HEC-HMS Model, one of the freeware semi-distributed models commonly used in hydrological analysis. The model input is the configuration of river networks generated from the National DEM (DEMNAS), hourly rainfall during floods and other watershed parameters such as land cover, soil types and river slope. The similar simulation was also carried out on the condition of the watershed before the earthquake. Based on the results of the analysis, It can be inferred that flash floods in the Bangga River are mainly caused by heavy rainfall with long duration and landslide areas in the upper watershed triggered by the 2018 Palu Earthquake with an area of approximately 10.8 km 2 . The greatest depth of rainfall as a trigger for flooding is 30.4 mm with a duration of 8 hours. The results of the study also showed that landslides in the upper watershed could increase the peak flood by 33.33% from 118.56 m 3 /s to 158.08 m 3 /s for conditions before and after the earthquake.

Baseflow is essential for water resource management in the dry season at the watershed scale. Management strategy water resources play a crucial role, especially those related to estimation efforts water supply, water quality management, water balance calculation, and strategy development of other water resources. This study aims to determine the value of baseflow using the Fixed Interval Method. This study used Hydro Office software with input daily discharge data from 2004 to 2013. The average baseflow value obtained was 5.53 m3/s, the process of calibrating by taking discharge data in the dry season, with no rainfall input. The BFI value obtained an average of 0. 9. This value indicates that the Miu watershed has high storage permeability characteristics. It indicates that the Miu watershed has a relatively stable flow during dry periods. The greater the BFI value, the better the water supply in a watershed.

The safe and clean water is necessary to the most of rural community. Slow sand system was proven to be sustainable and reliable drinking water treatment The majority of Sambo community using river as a source their daily activity. The water of the river containing a very high degree of contamination. The purpose of this study is to determine the model of Wisolo River Water treatment in order to obtain Clean Water in Sambo Village and then checked whether the physical content of the river water meets the water quality standard. From the results of the study using 3 (three) models of Wisolo River water filter processing layer variations, which are most ideal to use and meet the physical quality standards of clean water based on the Regulation of the Minister of Health of the Republic of Indonesia, the layer variations in model I, namely with successive material composition from bottom to top: gravel = 20 cm, palm fiber = 20 cm, and sand = 50 cm.