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Journal : Semesta Teknika

Kajian Erosi Pada Sub Das Serayu Sebagai Daerah Tangkapan Air Waduk Mrica Surya Budi Lesmana
Semesta Teknika Vol 23, No 2 (2020): NOVEMBER 2020
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v23i2.12082

Abstract

Pada daerah pertanian lahan kering serta memiliki tingkat kelerengan yang curam, erosi dan sedimentasi mendai salah satu problematika yang sering terjadi. Erosi akan dapat mengakibatkan kerugian pada lahan yaitu berakibat pada turunnya produktivitas lahan akibat kerusakan sifat-sifat fisik, kimia dan biologi. Dampak akibat adanya erosi antara lain umur waduk yang menjadi lebih pendek karena terjadinya pendangkalan, elevasi permukaan dasar sungai yang semakin naik karena adanya endapan sedimen, dan juga lahan pertanian yang rusak akibat adanya timbunan sedimen. Aktivitas manusia yang beragam pada Daerah Aliran Sungai akan mempengaruhi erosi ang terjadi. Analis perhitungan erosi untuk wilayah yang luas diperlukan untuk perencanaan pengelolaan dan konservasi. Penelitian ini bertujuan untuk menganalisis tingkat erosi di wilayah Sub DAS Serayu, yang merupakan salah satu daerah tangkapan air Waduk Mrica. Analisis perhitungan erosi menggunakan rumusan Universal Soil Loss Equation (USLE) dan Sistem Informasi Geografis (SIG). Curah hujan merupakan komponen untuk menghitung erosivitas hujan. Faktor vegetasi (C) dan faktor konservasi (P) diperkirakan dari peta penggunaan lahan. Faktor panjang dan kemiringan (LS) dianalisa dari Digital Elevation Model, dan faktor erodibilitas (K) diperoleh dari interpretasi peta tanah. Selanjutnya, semua faktor dianalisis untuk menghitung laju erosi. Hasil penelitian menunjukkan bahwa Sub DAS Serayu menghasilkan erosi sebesar: 11.877.576,89 T/th. Laju erosi rata-rata pada Sub DAS Serayu tergolong dalam erosi sedang, yaitu sebesar 166.35 T/ha/th. Hasil penelitian juga menunjukkan bahwa Universal Soil Loss Equation mampu memprediksi erosi yang cepat untuk area yang luas.steep slopes. Erosion has the potential to cause land losses in the form of physical, chemical, and biological property damage, resulting in a decrease in land productivity. Shorter reservoir life due to siltation, increased river bed surface elevation due to sediment deposits, and agricultural land damage due to sediment accumulation are all effects of erosion at the watershed. For management and conservation planning, analysts on erosion calculations for large areas are required. The purpose of this research is to assess the level of erosion in the Serayu sub-watershed, which is one of the Mrica Reservoir's water catchment areas. The USLE (Universal Soil Loss Equation) formula and Geographic Information System (GIS) are used in erosion calculation analysis. Rainfall data is used to calculate the erosivity factor. The land use map was used to calculate the vegetation factor (C) and conservation factor (P). The length and slope factor (LS) were calculated using the Digital Elevation Model, and the erodibility factor (K) was determined using the soil map interpretation. In addition, all factors were considered in order to calculate the erosion rate. The Serayu sub-watershed resulted in erosion of 11.877.576.89 T/year, according to the results. The average erosion rate in the Serayu sub-watershed is 166.35 T/ha/yr, which is classified as moderate erosion. The findings also demonstrate that USLE can be used to forecast rapid erosion over large areas. 
Analisis Drainasi di Saluran Cakung Lama Akibat Hujan Maksimum Tahun 2013 dan 2014 Puji Harsanto; Surya Budi Lesmana; Sherly Devianty
Semesta Teknika Vol 17, No 2 (2014): NOVEMBER 2014
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v17i2.416

Abstract

Flooding is an annual disaster for Indonesia. Jakarta is a city that each year nearly always experienced by flooding. The rapid development made the impervious area dropped drastically. Micro drainage is not capable of passing the volume of direct runoff. It makes many regions in Jakarta experienced by floodwaters. The aim of this research is to analyze the micro drainage capacity in Cakung Lama River. Simulations are performed with HEC-RAS 1D. The flood data is maximum rainfall on 2013 and 2014. Two scenarios normalization is done for reducing the inundated area around the river. Based on the simulation results, the existing conditions are not able to accommodate the discharge due to maximum rainfall 2013 dan 2014. Normalization of the river will give good results if the width of the river 5 m and the depth of the river is 3 m.
Evaluasi Muka Air Cakung Drain Hilir terhadap Hujan Maksimum 2013 dan 2014 Puji Harsanto; Muhammad Arif Banjaran Sari; Surya Budi Lesmana
Semesta Teknika Vol 17, No 1 (2014): MEI 2014
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v17i1.406

Abstract

Cakung floodway is a drainage channel that plays an importance rule for the overall of drainage system in Jakarta. Rainfall in 2013 and 2014 produced a big flood in Jakarta. Based on flood map Jakarta 2013 and 2014, there are inundated areas due to 2013’s and 2014’s rainfall. So, it is necessary to analyze the flood water level in channel floodway. Using HEC-RAS, this study aimed to evaluate the water level due to the maximum rainfall in 2013 and 2014. HEC-RAS is a tool for 1D hydraulic modeling and has reliability in routing of canal water level or river flooding. The results show that the maximum rainfall in 2013 provides a significant increasing of water level in Cakung floodway compared with the maximum rainfall in 2014. Soon, the need for canal normalization to reduce flood water level in Cakung floodway should be considered.