DESIGN FLOOD OF THE MAHAKAM LAKE CASCADE FOR REDUCING THE FLOOD DOWNSTREAM

The Mahakam lake cascade consists of Jempang, Melintang, and Semayang lakes. The cascade lakes have a complex hydrological system; the three lakes merged with the Mahakam River when flooding. Generally, analysis like that focuses on each lake; however, the cascade lakes are analyzed as a system in this research. In the dry season, the water is receding, and in the riparian part is becoming dry land even it is only left on the depth channel that is flooded. The extreme recede condition happened in 1997 during 192 days; however, the longest extreme flood condition lasted for 63 days in 2006. The lake function, which should be able to reduce the flood, cannot work optimally. Floods in this area happened every rainy season. This research intends to analyze the design flood that can still be stored by the storage capacity in each cascade lake (Jempang, Melintang, and Semayang). Therefore, the lake function for reducing the flood in this area can be optimized. The methodology consists of measuring water level depth in the lake multiplying by the lake section area, then conversed into discharge using the rational method. The lake boundaries were determined by spatial analyses that is GIS application. The result shows that the design flood in each lake is varied and depends on each lake capacity. The capacity of the Jempang lake is only for the design flood Q25, about 388.33 m3/s; the Melintang lake can only store the design flood Q10 that is about 140.10 m3/s, and the Semayang lake is only able to store the design flood Q25 that is about 82.05 m3/s. This result can be used as a reference to design the optimization model for reducing the flood downstream.

Penerapan Perilaku Hidup Bersih dan Sehat (PHBS) Desa Wonosalam Demak

Wonosalam Village is located on the banks of the Tuntang river which is the largest river in Demak. High rainfall often causes the overflow of the river to flood and cause seasonal diseases. This flood condition is exacerbated by the relatively low awareness of the community's clean life as seen from the large amount of waste that has not maintained well and the low quality of health of the residents of Wonosalam Village. The objectives of the activity are: 1) to find out the level of awareness of the community's PHBS; 2) provide practical understanding of clean and healthy life; 3) familiarize community control on PHBS, 4) improve the quality of a clean and healthy life. The methods used are surveys, lectures, discussions, and demonstrations. The results of this activity are 1) the level of understanding of residents and students as community partners regarding PHBS increases; 2) residents of Wonosalam village and students can perform several behaviors, such as washing hands with soap, exercising, brushing teeth, and carrying out proper waste disposal management; 3) residents and teachers can remind each other if there are residents or students who do not practice PHBS behavior; 4) the environment of Wonosalam villagebecomes more beautiful and clean and residents become more enthusiastic about living life.

DESAIN SABO DAM TIPE CONDUIT SEBAGAI PENGENDALI DAYA RUSAK ALIRAN DEBRIS

ABSTRAKSungai Air Kotok di Kabupaten Lebong, Bengkulu memiliki litologi batuan yang rapuh akibat pengaruh panas bumi, kondisi tersebut menyebabkan rentan mengalami pergerakan massa tanah/batuan. Oleh karena itu, diperlukan upaya mitigasi untuk mengurangi risiko bencana dengan perencanaan bangunan pengendali aliran debris berupa sabo dam. Penelitian ini bertujuan untuk merencanakan desain sabo dam tipe conduit yang dirancang secara seri dan mengevaluasi stabilitas sabo dam berdasar SNI 2851:2015. Hasil perhitungan menunjukkan debit puncak untuk kala ulang 100 tahun sebesar 171,21 m3/detik. Empat seri sabo dam memiliki dimensi lebar pelimpah rerata ± 40 m, kedalaman aliran debris sebesar 1 m, dan tinggi pelimpah ialah 2,4 m. Stabilitas sabo dam saat banjir diperoleh faktor aman untuk stabilitas geser dan guling sebesar 3,46 ; 1,62. Adapun faktor aman terhadap pengaruh aliran debris untuk stabilitas geser dan guling adalah 3,30 ; 1,58. Berdasarkan hasil analisis, empat seri sabo dam tipe conduit yang dirancang mampu mengendalikan daya rusak banjir maupun aliran debris.Kata kunci: Hidraulika sungai, aliran sedimen, bangunan sabo, stabilitas sabo ABSTRACTAir Kotok River in Lebong Regency, Bengkulu Province has the lithology of weathered rock which is a result of geothermal process, this condition causes to be susceptible to land / rock mass movements. Therefore, the mitigation efforts are needed to reduce the risk from disaster by design debris flow control such as sabo dam. This study aims to design series of conduit type sabo dam and evaluate the stability based on SNI 2851: 2015. The calculation shows that the peak discharge for the 100-year return period is 171.21 m3 / sec. The four sabo dam series have dimensions of spill width of ± 40 m, debris flow depth of 1 m, and overflow height of 2.4 m. The stability of sabo dam has safety factor in flood condition for shear and overturning stability are 3.46; 1.62, while in a debris flow condition for shear and overturning stability are 3.30; 1.58. Based on the results, the four series of conduit sabo dam are able to control the destructive power of floods and debris flows.Key word: River hydraulic, sediment flow, sabo building, stability of sabo

Identifikasi Penentuan Skala Prioritas Penanganan Genangan Atau Banjir Di Kecamatan Karawang Barat

West Karawang District is a center of local activities with a service scope the whole Karawang Regional with most populous region by 142.509 persons. Based on Karawang Regional Spatial Plans Year 2011 – 2031, West Karawang Sub-district is a flooded vulnerable area when rain season. That area is along the Citarum River stream with. Priority scale determination of flood is done with comparison method of the existing flood condition with the parameters in Peraturan Menteri Pekerjaan Umum dan Perumahan Rakyat No.12 Tahun 2014 tentang Penyelenggaraan Sistem Drainase Perkotaan. There were 13 flood points in West Karawang District with the highest priority scale, Tanjungpura Sub-District. In Tanjungpura Sub-District, there are 3 flood points with a height of 50-30 cm, 1 Ha of flood area, and the length of flood lasts for 10 hours. The puddle is located in a densely populated residential area which causes a lot of losses to residents.

Physics-based Bathymetry and Water Quality Retrieval Using PlanetScope Imagery: Impacts of 2020 COVID-19 Lockdown and 2019 Extreme Flood in the Venice Lagoon

The recent PlanetScope constellation (130+ satellites currently in orbit) has shifted the high spatial resolution imaging into a new era by capturing the Earth’s landmass including inland waters on a daily basis. However, studies on the aquatic-oriented applications of PlanetScope imagery are very sparse, and extensive research is still required to unlock the potentials of this new source of data. As a first fully physics-based investigation, we aim to assess the feasibility of retrieving bathymetric and water quality information from the PlanetScope imagery. The analyses are performed based on Water Color Simulator (WASI) processor in the context of a multitemporal analysis. The WASI-based radiative transfer inversion is adapted to process the PlanetScope imagery dealing with the low spectral resolution and atmospheric artifacts. The bathymetry and total suspended matter (TSM) are mapped in the relatively complex environment of Venice lagoon during two benchmark events: The coronavirus disease 2019 (COVID-19) lockdown and an extreme flood occurred in November 2019. The retrievals of TSM imply a remarkable reduction of the turbidity during the lockdown, due to the COVID-19 pandemic and capture the high values of TSM during the flood condition. The results suggest that sizable atmospheric and sun-glint artifacts should be mitigated through the physics-based inversion using the surface reflectance products of PlanetScope imagery. The physics-based inversion demonstrated high potentials in retrieving both bathymetry and TSM using the PlanetScope imagery.

ANALISA PENGENDALIAN BANJIR AKIBAT PELUAPAN DEBIT ALIRAN DENGAN PERKUATAN TEBING TIPE SHEET PILE “Studi Kasus Sungai Batang Lumpo Kabupaten Pesisir Selatan”

Flooding ia caused by the increased volume of water’s volume in the river or lake so that water is out of its natural limits. The flooding is mostly caused by inadequate river capacity to accommodate river discharge. The amount of river discharge at the time of flood is caused by the increasing amount of surface runoff from the rains that fall in the catchment area. Based on the preliminary survey conducted, it was found that the frequency of flooding in the Batang Lumpo river area is 2-3 times a year with a height ranging from 0.5 to 1.5 meters from the soil surface with the duration of inundation ranges from 4 to 6 hours. Areas affected by flooding ranging from the area of Nagari Taratak Tengah Lumpo Kecamatan IV Jurai down to the downstream river at Nagari Pasar Baru Kecamatan Bayang. By the result of the analysis obtained flood discharge using Rational method Q 100 years = 237, 26 m³ / dt, high h = 2.7 m, the high value of W = 1.16 m length Sheet Pile in flood condition = 4.14 m, Maximum Moment Mmax = 6, 31 tm and sheet pile length in dry condition = 3.16 m, Mmax Moment = 7,125 t.m.

Dendroindication of ecoclimatic condition in forest remediation area within Northern Steppe of Ukraine

We analyzed ring width, latewood width and earlywood width of Pinus sylvestris trees under normal and flood condition in Dnipropetrovsk region, within Northern Steppe of Ukraine. Precipitation from February to August seems to be the most stable climatic factor which influenced Scots pine growth rate and caused the difference between maximum and minimum ring width in normal conditions. Meteorological conditions were mainly associated with general ring values and earlywood width, and were less associated with latewood width values. Assessment of the effect of climatic signals on tree rings’ growth process in living and dead trees and in the normal and flood condition by analyses of correlation and response function was conducted. Average annual temperatures affected the tree growth negatively in normal conditions and tree increment positively in flood conditions. Annual precipitation was correlated positively with ring width, earlywood width series in normal conditions, but negatively with these series in flood conditions.

DAUN ANGSANA SEBAGAI ALTERNATIF PEMBUATAN KOMPOS DENGAN METODE BIOPORI PADA KONDISI BANJIR TAHUN 2016

Surabaya is one of frequently flooded city in Indonesia. The installation of box culvert and Angsana tree planting on the roadside are efforts to minimize flooding. The Angsana tree planting have an impact in the form of excessive leaf waste. Processing the leaves as compost is one effort to reduce the waste. Composting is carried out by using biopori method. Biopori method was chosen since it can be used for composting and serves as a rainwater catchment pit. This is a descriptive study which compare the results of composting by using biopori method on flood conditions and non-flood condition. The results were adjusted to SNI compost. The C/N ratio and composting time are two big considerations in this research. The survey results revealed that the average of C/N ratio was 48.43 before composting, 12.60 after composting in flood conditions and 18.06 in non-flooded condition. The average of temperature, humidity and pH after composting in flood condition were 38℃, 65% and 7 respectively, while after composting at non-flooding were 41°C, 55%, and 7 respectively. The physical condition after composting in flood and non-flood conditions was the same, dark brown-black, ground smell, and soft and easily crushed, yet on flood condition was more friable resembles soil more. The duration needed for the composting process in flood and non-flood condition was the same by 23 days. In flood condition, the shrinkage was faster than in non-flood conditions. In flood condition, the humidity was very high that sawdust was added little by little and the compost was stirred regularly to reduce humidity. Keywords : AngsanaLeaf, Biopori, Compost