Cross-Sectional Engineering for Lombagin River Flood Management, Bolaang Mongondow Regency

Abstract

The Lombagin River located in Bolaang Mongondow Regency is one of the longest rivers in the Bolaang Mongondow area. This river is upstream located in Nani Wartabone National Park, Bolaang Mongondow Regency, flows through several districts and empties into the Sulawesi sea. This river is an important river for the people of Bolaang Mongondow, is a source of water to meet various needs especially to irrigate many Irrigated Areas in the area. The main problem today is that rivers often overflow during the rainy season. River overflow water inundated settlements, highways and existing rice fields, resulting in disruption of people's lives, damage to public facilities and infrastructure, crop failure and damage to rice fields and other losses that were not small.

This research aims to obtain the best cross-sectional design to overcome flooding with a 50-year anniversary on the Lombagin river.

The steps taken in this study include: collecting secondary data in the form of discharge data from debit posts in the watershed. Perform data quality analysis. Analyze the frequency of discharge data to obtain the planned discharge. Water level analysis with the help of the HEC-RAS program. Analysis of the best cross-sectional design by creating flooded dikes.

The results obtained, at the time of the 5-year flood anniversary, all the left dikes were safe, while the right embankment overflowed from River Station 14 to 27 with different overflow heights. At the time of the 50th anniversary, all the left levees were still safe, while the right embankment, there was an overflow from River Station 2 to 27, only at River station 1 did not overflow. Flood management will be calculated with a 50-year anniversary. To cope with flooding by 50 years anniversary, the cross-section of the river must be engineered. Cross-sectional engineering by enlarging the cross-sectional area of the river. The method chosen was to add an embankment along the right bank of the river. The additional height of the embankment varies from 0.96 meters to 6.34 meters.