Pengembangan Model Eco-Riprap Perkuatan Tebing Sungai Untuk Memulihkan Kualitas Habitat Litoral Kali Surabaya

Rini, Daru Setyo (2017) Pengembangan Model Eco-Riprap Perkuatan Tebing Sungai Untuk Memulihkan Kualitas Habitat Litoral Kali Surabaya. Doctor thesis, Universitas Brawijaya.

Abstract

Perairan sungai dan sempadan sungai adalah salah satu tipe ekosistem perairan darat yang yang sangat penting namun terancam oleh meningkatnya aktivitas manusia yang berdampak pada kerusakan habitat alami sungai (Tocker & Stanford, 2002; Welcomme, 1985). Berkurangnya vegetasi alami sempadan sungai, erosi tebing sungai, modifikasi aliran alami sungai dan penurunan kualitas air mengakibatkan hilangnya habitat ideal bagi biota perairan sungai. Untuk mencegah kerusakan habitat sungai diperlukan pengelolaan aliran sungai dan sempadan sungai secara efektif dan terpadu (Stromberg et al. 2004). Peraturan Pemerintah Nomor 32 tahun 2008 tentang Pengelolaan Sungai menyebutkan bahwa sungai yang sehat tercermin dari berkembangnya kehidupan berbagai jenis flora dan fauna sungai. Pemerintah wajib melakukan restorasi sungai untuk mencegah kerusakan berlanjut pada ruas sungai tertentu dan sungai yang rusak direncanakan agar menjadi ruas sungai yang sehat kembali. Perlindungan ruas restorasi sungai bertujuan untuk mengembalikan sungai ke kondisi alami melalui kegiatan fisik dan rekayasa secara vegetasi. Peraturan Pemerintah Republik Indonesia Nomor 26 Tahun 2008 tentang Rencana Tata Ruang Wilayah Nasional dalam Pasal 52 menetapkan sempadan sungai sebagai kawasan lindung nasional yang dikelola sebagai kawasan perlindungan setempat oleh Pemerintah Daerah. Pengembangan konstruksi struktur perkuatan tebing sungai dalam rekayasa hidrolika konvensional lebih mengutamakan aspek efektivitas pengaliran air dan pengaliran sedimen sungai dengan konstruksi tembok masif yang kedap air dan membutuhkan biaya tinggi. Rekayasa hidrolika konvensional cenderung mengabaikan dampak ekologis terputusnya koneksi zona riparian dan aliran air sungai yang dapat mengganggu keseimbangan siklus hidrologi dan ekologi sungai serta menghilangkan habitat alami riparian dan keragaman hayati biota sungai. Penelitian ini mempromosikan penerapan model rekayasa ekohidrolika untuk meningkatkan stabilitas tebing sungai. Rekayasa ekohidrolika dilakukan dengan menggabungkan model yang telah dikembangkan sebelumnya oleh Brisbane City Council (2000) dan McCullah and Gray (2005), serta menambahkan komponen vegetasi riparian lokal pada tebing sungai yang mengalami erosi. Lingkup wilayah penelitian dibatasi pada segmen Kali Surabaya pada dataran rendah dengan kecepatan arus kurang dari 1 mdet-1 dan ketinggian tebing kurang dari 3 meter. Lokasi penelitian terdiri dari 6 stasiun penelitian yaitu Perning, Sumberame, Wringinanom, Penambangan, Klubuk dan Lebaniwaras, yang dikelompokkan menjadi 4 kategori yaitu Lokasi Acuan atau Reference Site (Perning), Tanpa Perlakuan atau Unrestored (Sumberame, Penambangan, Lebaniwaras) serta Sebelum Perlakuan atau Pre-Restored (Wringinanom dan Klubuk) dan Setelah Perlakuan atau Post-Restored (Wringinanom dan Klubuk). Parameter hidrolika yang dikaji meliputi profil penampang palung sungai, komposisi butiran substrat, kemiringan tebing sungai, tutupan vegetasi, kecepatan arus tepi sungai, dan parameter kualitas air (suhu, kekeruhan, jumlah xii oksigen terlarut). Parameter biologi yang dipantau adalah kelimpahan, keanekaragaman jenis, komposisi dan indeks diversitas makroinvertebrata dan ikan. Waktu pengamatan dilakukan selama musim hujan dan musim kemarau 2014 - 2016. Uji statisitika dilakukan menggunakan software PAleontological STatistik PAST versi 3.12 (Hammer, 2016). Uji Mann Whitney Pairwise dilakukan untuk mengetahui perbedaan kondisi habitat litoral dan komunitas biota antara lokasi penelitian. Uji korelasi Kendalls tau dilakukan untuk mengetahui hubungan suatu parameter habitat litoral sungai dengan komunitas biota makroinvertebrata. Analisis statistika multivariate Principle Component Analysis (PCA) digunakan untuk mengetahui korelasi antar parameter utama habitat litoral sungai yang secara kolektif mempengaruhi komunitas biota makroinvertebrata. Hasil analisis rerata debit air Kali Surabaya 2009-2016 menunjukkan periode musim hujan terjadi pada bulan Desember sampai Mei dengan rerata debit air di atas 50 m3/s, yaitu berkisar antara 57,5 - 74,6 m3det-1. Musim kemarau terjadi pada bulan Juni - November dengan rerata debit air kurang dari 50 m3det-1, berkisar antara 31,52 m3det-1- 48,33 m3det-1. Rerata debit tertinggi sebesar 94,21 m3det-1 terjadi pada Januari 2013 dan rerata debit terendah sebesar 20,58 m3det-1 pada Oktober 2014. Tahun 2013, 2015 dan 2016 debit air maksimum saat musim hujan tercatat lebih dari 90 m3det-1. Sepanjang tahun 2013 dan 2016 debit rata-rata Kali Surabaya tercatat lebih dari 40 m3det-1, mengindikasikan tidak terjadi musim kemarau yang nyata pada tahun 2013 dan 2016. Penghitungan koefisien rejim aliran sungai Kali Surabaya (Qid) diperoleh dengan membandingkan debit maksimum dan debit minimum (Qmax/Qmin) selama periode 2009 - 2015 menghasilkan rasio sebesar 2,1 - 4,5. Nilai Qid mengindikasikan Sub DAS Kali Surabaya termasuk dalam kategori kualitas baik. Kondisi bantaran sungai umumnya masih terpelihara dan bervegetasi alami sehingga dapat menampung dan melokalisir luapan air sungai, sehingga akan mengurangi debit air sungai ke wilayah hilir. Kondisi bantaran sungai bervegetasi alami di Kawasan Suaka Ikan Kali Surabaya pada segmen Mlirip sampai Legundi masih cukup baik. Untuk itu perlu upaya pemeliharaan dan penanaman vegetasi asli tepi sungai serta mengendalikan pemanfaatan lahan bantaran oleh masyarakat agar tidak mengganggu fungsi kawasan lindung bantaran sungai. Hasil analisis data penelitian menunjukkan bahwa penerapan rekayasa ekohidrolika perkuatan tebing sungai berdampak pada stabilitas tebing, mengubah morfologi tebing sungai dan meningkatkan kualitas air Kali Surabaya. Perubahan morfologi dasar kaki tebing disebabkan oleh penambahan riprap batu kali dan groyne segitiga kayu. perkuatan dasar kaki tebing mengurangi gerusan arus di dasar sungai yang menyebabkan erosi bawah tebing (undercut bank) dan longsor tebing sungai agar menciptakan mikrohabitat baru bagi beragam biota sungai. Di kedua lokasi perlakuan rekayasa ekohidrolika terjadi peningkatan keragaman jenis taksa makroinvertebrata dan keragaman jenis taksa Ephemeroptera Plecoptera Trichoptera (EPT), peningkatan persentase kelompok serangga Ephemeroptera Plecoptera Trichoptera (%EPT) dan persentase udang air tawar (%Atyidae) serta penurunan persentase cacing darah (%Chironomidae). Komunitas ikan di segmen Wringinanom - Klubuk mengalami peningkatan keragaman jenis ikan, peningkatan kelimpahan individu ikan sebesar 54,2% serta peningkatan persentase kelimpahan ikan jendil (Pangasius micronemus) sebesar 25,6% dan peningkatan persentase kelimpahan ikan rengkik (Hemibragus nemurus) sebesar 6,3 % pada segmen Wringinanom - Klubuk, serta munculnya jenis ikan yang jarang ditemukan yaitu ikan bloso (Oreochemis marmorata), berot (Mastacembelus unicolor), palung (Hampala macrolepidota) dan papar (Notopterus notopterus).

English Abstract

River and river bank is a type of ecosystem in inland waters that has important roles but it is been threatened by increasing human activities that give negative impacts on destruction of natural riparian habitat (Tocker & Stanford, 2002; Welcomme, 1985). Declining of natural riparian vegetation, bank erosion, channel modification and deterioration of water quality lead to degradation of natural habitat for river's organisms. To prevent habitat degradation, it is urgent to improve river and riparian management in integrated and effective way (Stromberg et al. 2004). Government Regulation No. 32/2008 on River Management declare that healty river is reflected by thriving of various native flora and fauna. Government is mandated to execute river restoration to prevent river degradation occurs continuously at certain river reach and to restore degraded river into healthy condition. River protection and restoration aims to improve river status by physical and vegetation modification. Government Regulation No. 26/2008 on National Spatial Planning Article 52 declare that river bank or floodplain area are served as national conservation area under management authority of Regional Government. Current hydraulic approach set a high priority on effectiveness of water flow and sediment flow by construction of massive cemented wall that highly impermeable and high cost, otherwise it neglects ecological impacts on lost of connection between river channel and its riparian land disrupts hydrological cycle and ecosystem balance as well as lost of riparian habitat and extincition of river biodiversity. This research promotes application of ecohyraulic engineering to increase bank stability by combining model of bank protection by Brisbane City Council (2000) and Mc Cullah and Gray (2005), and additioin of native riparian vegetation on bank slope and riparian land along eroded river reach. The research area is limited to segment of Surabaya River at lowland elevation with current velocity lesser than 1 m/s and bank height was lower than 3 meter. The research sites were located in six stations, i.e. Perning, Sumberame, Wringinanom, Penambangan, Klubuk dan Lebaniwaras, that was grouped into 4 categories, namely Reference Site (Perning); Unrestored (Sumberame, Penambangan, Lebaniwaras); Pre-Restored (Wringinanom and Klubuk); and Post-Restored (Wringinanom dan Klubuk). Hydraulic parameter measured were channel cross section, substrate composition, bank slope, vegetation cover, near-bank velocity, and water quality parameter (temperature, turbidity, and dissolved oxygen). Biotic parameter measured were abundance, richness, composition, diversity index of macroinvertebrates and fishes community. The field research was done during rainy and dry seasons in year 2014 to 2016. Statistical analysis was done using software PAleontological STatistik PAST version 3.12 (Hammer et al, 2001). Mann Whitney Pairwise Test was xiv carried out to analysis the difference among locations. Correlation test Kendalls tau was run to analyse correlation among parameters. Statistical analysis multivariate Principle Component Analysis (PCA) was run to identify principal components of each location, specific habitat condition and its impacts on macroinvertebrate community. The results showed that average monthly discharge of Surabaya River from year 2009 to 2016 indicates that rainy season period occured during December to May with above 50 m3s-1, range from 57,5 to 74,6 m3s-1. Dry season occured from June to November with average monthly discharge was less than 50 m3s-1, the water discharge was 31,52 to 48,33 m3s-1. The highest average discharge was 94,21 m3s-1 that occured on Januari 2013 and the lowest average was 20,58 m3s-1 that occured in October 2014. In year 2013, 2015 and 2016, the highest average discharge in rainy season was above 90 m3s-1. In 2013 and 2016, the average low discharge was more than 40 m3s-1 that indicated less significant dry season. River regime coefficient (Qid) of Surabaya River was calculated by comparing maximum discharge to minimum discharge (Qmax/Qmin) during 2009 to 2015, that given ratio score ranged from 2,1 to 4,5. This Qid value indicated that Surabaya River subbasin categorized into good quality. The riparian condition mostly still covered by natural vegetation thus it served as flood retention zone that localize floods in the floodplain area and reduce floods to dowstream area. Riparian area with natural vegetation in Fishery Sanctuary Area of Surabaya River from Mlirip to Legundi were found, that is need to be protected by government regulation to control human activity and land use convertion of riparian area. Application of ecohyraulic engineering bank protection model showed positive impacts on bank stability improvement, bank morphology and water quality of litoral water. The bank morphology was improved by addition of riprap or boulder placement at the bank toe and groyne triangle structure of large woody debris. All trearments protected bank toe from shear scour that cause undercut bank and bank failure, as well as developed new microhabitat conditions for river organisms. At both treatment sites of ecohydraulic engineering, it showed increasing of taxa richness, EPT taxa richness, %EPT and %Atyidae, and decreasing of %Chironomidae in macroinvertebrate community. In Wringinanom - Klubuk reach, it showed increasing of taxa richness and fish abundance was increased by 54,2%, abundance of Pangasius micronemus increased by 25,6%, and abundance of Hemibragus nemurus increased by 6,3 %. The rare fish species also were found at treatment area in Wringinanonm - Klubuk reach, namely Oreochemis marmorata, Mastacembelus unicolor, Hampala macrolepidota and Notopterus notopterus.

Item Type:	Thesis (Doctor)
Identification Number:	DIS/333.91/RIN/p/2017/061707590
Uncontrolled Keywords:	RIPRAP, EMBANKMENTS, LITTORAL PLANTS, RIVER CHANNELS
Subjects:	300 Social sciences > 333 Economics of land and energy > 333.9 Other natural resources > 333.91 Water and lands adjoining bodies of water
Divisions:	Program Pascasarjana > Doktor Kajian Lingkungan, Program Pascasarjana
Depositing User:	Nur Cholis
Date Deposited:	29 Aug 2017 01:46
Last Modified:	27 Dec 2020 16:49
URI:	http://repository.ub.ac.id/id/eprint/1801

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