Electronic Theses and Dissertation

Banjir merupakan masalah yang sering terjadi, terutama di kawasan pemukiman, baik perkotaan maupun pedesaan. Berdasarkan informasi dari masyarakat banjir di Sungai Krueng Buloh terjadi hampir setiap tahun pada bulan November hingga Januari, dengan durasi banjir berkisar antara 3 hingga 5 hari dan ketinggian air 0,5 meter hingga 1 meter. Kerusakan yang ditimbulkan cukup besar, erosi tepian sungai berkisar antara 1 hingga 3 kilometer sepanjang sungai dan perubahan penampang sungai memperburuk kondisi Sungai Krueng Buloh. DAS Sungai Krueng Buloh rentan terhadap banjir besar, yang menimbulkan banyak dampak sosial dan ekonomi terhadap desa-desa di sekitarnya, seperti hilangnya hasil panen dan rusaknya bangunan. Permasalahan yang terjadi di DAS Krueng Buloh di Provinsi Aceh antara lain curah hujan yang tinggi dan ketidakmampuan sungai dalam menampung debit pada saat hujan serta masih meluasnya genangan banjir pada sungai Krueng Buloh. Penelitian ini bertujuan untuk mengetahui faktor-faktor yang mempengaruhi kestabilan alur sungai di wilayah hilir DAS Krueng Buloh pasca banjir, kondisi hidrologi dan hidrolika Kawasan Krueng Buloh dan mengetahui luas genangan banjir setelah penanganan infrastruktur pengendali banjir. Untuk mencapai tujuan ini, observasi hidromorfologi DAS Krueng Buloh berbasis lapangan dan satelit telah dilakukan. Metodologi penelitian meliputi analisis morfologi sungai, analisis hidrologi, analisis hidrolika, analisis sedimentasi, dan penanganan infrastruktur. Pemodelan banjir dengan menggunakan model matematika HEC-RAS, ArcGIS untuk pengolahan data spasial serta HEC-GeoRAS untuk antarmuka antara ArcGIS dan HEC-RAS. Investigasi mengungkapkan bahwa curah hujan yang berlebihan, meandering sungai, dan jenis tanah tepian sungai memicu banjir dan penumpukan sedimen di dataran banjir maka dilakukan penanganan infrastruktur di Sungai Krueng Buloh. Berdasarkan hasil penelitian luas area genangan periode ulang 2 tahunan dan periode ulang 5 tahunan tidak terjadi banjir. Luas area genangan periode ulang 10 tahunan sebesar 585,21 Ha menjadi 326,91 Ha (55,86%). Luas area genangan periode ulang 25 tahunan sebesar 1.321,38 Ha menjadi 453,81 Ha (34,34%). Luas area genangan periode ulang 50 tahunan sebesar 1.791,28 Ha menjadi 1.390,49 Ha (77,63%). Luas area genangan periode ulang 100 tahunan sebesar 2.626,87 Ha menjadi 2.246,5 Ha (85,52%). Dari hasil pemodelan tersebut dapat diketahui bagian mana yang terjadi limpasan. Adanya pengurangan luas genangan banjir sampai dengan 64,78% dari hasil simulasi periode ulang yang telah dilakukan. Dengan adanya tanggul tidak mengubah debit banjir, melainkan hanya berdampak pada perubahan luasan genangan dan tidak merubah ketinggian banjir. Luas genangan banjir di kawasan Sungai Krueng Buloh dipengaruhi oleh kapasitas aliran sungai, kondisi morfologi sungai, jenis tanah serta efektivitas infrastruktur pengendali banjir seperti tanggul. Infrastruktur yang memadai dan perawatan sungai yang baik dapat mengurangi luas genangan banjir.

Kata kunci: Banjir; Daerah Aliran Sungai, Morfologi, Sedimentasi, Infrastruktur.

Flooding is a frequent problem, especially in residential areas, encompassing both urban and rural regions. Based on information from the community, floods in the Krueng Buloh River occurs almost every year from November to January, with flood durations ranging from 3 to 5 days and water levels from 0.5 meters to 1 meter. The damage caused is significant, with riverbank erosion ranging from 1 to 3 kilometers along the river and changes in river cross-sections worsening the condition of the Krueng Buloh River. The River Krueng Buloh watershed is prone to severe flooding, which has many social and economic effects on the villages nearby, such as crop loss and building destruction. Problems in the Krueng Buloh River Basin in Aceh Province include high rainfall and the river's inability to accommodate discharge during rain, as well as the persistent spread of flood inundation in the Krueng Buloh River. This research aims to identify the factors affecting the stability of the river course in the downstream region of the Krueng Buloh River Basin after flooding, assess the hydrological and hydraulic conditions of the Krueng Buloh area, and determine the extent of flood inundation after the implementation of flood control infrastructure. To achieve these objectives, field- and satellite-based hydro morphological observations of the Krueng Buloh River Basin have been conducted. The research methodology includes river morphology analysis, hydrological analysis, hydraulic analysis, sedimentation analysis, and infrastructure management. Flood modeling was conducted using the HEC-RAS mathematical model, ArcGIS for spatial data processing, and HEC-GeoRAS as the interface between ArcGIS and HEC-RAS. The investigation revealed that excessive rainfall, river meandering, and the soil type along the riverbanks trigger flooding and sediment accumulation in floodplains, necessitating infrastructure interventions in the Krueng Buloh River. Based on the research findings, the flood inundation area for a 2-year and 5-year return period showed no flooding. The flood inundation area for a 10-year return period decreased from 585.21 ha to 326.91 ha (55.86%). The flood inundation area for a 25-year return period decreased from 1,321.38 ha to 453.81 ha (34.34%). The flood inundation area for a 50-year return period decreased from 1,791.28 ha to 1,390.49 ha (77.63%). The flood inundation area for a 100-year return period decreased from 2,626.87 ha to 2,246.5 ha (85.52%). The modeling results identified areas prone to overflow. There was a reduction in flood inundation area by up to 64.78% based on the simulation of the return periods conducted. The presence of levees does not alter the flood discharge but only impacts the change in inundation area and does not affect flood height. The flood inundation area in the Krueng Buloh River area is influenced by the river’s flow capacity, river morphology, soil type, and the effectiveness of flood control infrastructure such as levees. Adequate infrastructure and good river maintenance can reduce the extent of flood inundation. Keywords: Flood, Watershed, Morphology, Sedimentation, Infrastructure