The Use of Drop-Structures to Increase the Dissolved Oxygen Level along the Cibarani Channel

The Cikapundung river basin community uses the Cibarani channel as a drainage system and water source for fishing. However, the test result released on 9th November 2020 revealed that the channel’s water quality failed to reach the class II raw water standards due to various domestic waste discharges. This led to the performance of various studies to identify pollution control techniques by limiting the wastewater discharge and quality, controlling the intake discharge, and using baffles. The Cibarani channel has a drop-structure that can improve the water quality, though the effect has not been previously detailed. Therefore, this study was intended to comprehensively examine the effect of the drop-structure along the Cibarani channel to improve water quality conditions, specifically the Dissolved Oxygen (DO) parameter. This study employed the one-dimensional HEC-RAS software to simulate the hydrodynamic and water quality conditions along the Cibarani channel, and the drop-structure was modelled using two alternatives consisting of a vertical wall and a steep riverbed. Subsequently, the drop-structure fitted with a vertical wall gave a more plausible reaeration rate of 125 day-1 and Root Mean Square Error (RMSE) value of 0.50. The placement of a similar configuration before the first housing of the channel increased the DO concentrations by an average of 4.37 mg/L. This was followed by the modelling of another drop-structure after the first housing to increase the DO levels at the downstream part. Eventually, the combination of the two new drop-structures succeeded in increasing the DO concentrations along the Cibarani channel to 3.3 - 6.9 mg/L.

Flood Management of Diyala River

Diyala Governorate was recently exposed to high flood waves discharged from Hemrin Dam. Since the dam was at its full capacity during the flood period, these waves were discharged to the Diyala River. Because of the reduction in Diyala River capacity to 750m3/s, the cities and villages on both sides of the river banks were inundated. Thus, the study's objective is to design a flood escape out of the Diyala River, to discharge the flood wave through it. The flood escape simulation was done by using HEC- RAS software. Two hundred twenty-three cross sections for the escape and 30 cross-sections of the Diyala River were used as geometric data. Depending on the geological formation that the escape passed through, two roughness coefficients of 0.035 and 0.028 were applied. An outflow downstream Hemrin Dam varies from 1100m3/s to 1800m3/s was applied as boundary condition upstream Diyala River. One dimensional hydraulic model was developed for the escape and the river, the results showed that aside weir could be constructed at the escape entrance with crest level 67m.a.m.s.l. and 800m width, followed by drop structure of four rectangular steps, this case provides safe discharge to Diyala River if flood wave of 1500m3/s released from Hemrin Dam.

Managing the Flood Waves from Hemrin Dam

Diyala Governorate was exposed recently to high flood waves discharged from Hemrin Dam to Diyala River when the dam reached its full capacity. The recently recorded discharge capacity of Diyala River was reduced to just 750m3/s. This exposes cities and villages along the Diyala River to flood risk when discharging the flood waves, which may reach 3000 m3/s. It is important to manage, suggest, and design flood escapes to discharge the flood waves from Hemrin Dam away from Diyala River. This escape branches from Hemrin Lake towards Ashweicha Marsh. One dimensional hydraulic model was developed to simulate the flow within the escape by using HEC-RAS software. Eighty-two cross-sections were extracted from the digital elevation model for the escape and used as geometric data. Moreover, thirty cross-sections for the Diyala River were utilized from the Strategic Study for Water and Land Resources in Iraq. Since the escape passes through two regions of different geological formations, two roughness coefficients of 0.035and0.028were used. Two discharge cases were applied3000m3/s, which is the 500 years return period extreme hydrograph of Hemrin Dam, and 4000 m3/s, which is the design discharge of Hemrin Dam spillway. A spillway was proposed at the escape entrance with crest level 105m.a.m.s.l., followed by a drop structure with eighteen rectangular steps

APLIKASI TYRE DROP STRUCTURE PADA RANCANGAN DRAINASE DISPOSAL PIT NANGKA CV CINTA PURI PRATAMA

Disposal Pit Nangka merupakan area yang terindikasi mengalami erosi karena pengaruh kecuraman lereng, area timbunan dan tingginya intensitas hujan. Laju erosi menyebabkan terkikisnya tanah secara terus-menerus dan jika tanah tidak dapat menampung air maka akan menimbulkan longsor. Oleh karena itu diperlukan adanya perkuatan saluran.Pada penelitian ini, metode perhitungan curah hujan rencana menggunakan 4 (empat) distribusi dan dilakukan uji chi kuadrat untuk memilih distribusi yang cocok. Curah hujan rencana yang terpilih adalah sebesar 85,07 mm. Untuk penentuan catchment area menggunakan software didapat total catchment area sebesar 0,1438 km2, pada area 1 sebesar 0,0618 km2,area 2 sebesar 0,0446 km2 dan area 3 sebesar 0,0374 km2. Perhitungan debit limpasan menggunakan metode rasional pada Area 1 sebesar 2,65 m3/s, Area 2 sebesar 2,10 m3/s, dan Area 3 sebesar 1,89 m3/s. Terdapat dua dimensi saluran terbuka yaitu saluran tanpa ban dan saluran menggunakan ban. Dimana penempatan dimensi ban dipengaruhi oleh bilangan Froude sedangkan untuk mengetahui laju erosi menggunakan metode USLE.Hasil perhitungan menunjukan bahwa pada segmen-segmen dengan slope yang besar memiliki kecepatan aliran super kritis, sehingga segmen tersebut memerlukan perkuatan. Pendugaan erosi berdasarkan metode USLE pada tahun 2018 adalah sebesar 32.358,02 m3. Hal ini menyebabkan butuhnya perkuatan saluran dengan tyre drop structure agar kecepatan aliran dapat diminimalkan. Kata Kunci : catchment area, USLE, drop structure, laju erosi

Relocation Alternative of the Upstream Glonggong River due to Changes in Land Use

The gas production and processing unit's construction plan in the Jambaran-Tiung Biru Gas Plant project is within the Upstream Glonggong River catchment area. Planning arrangement of the Jambaran-Tiung Biru Gas Plant right above the Upstream Glonggong River will impact the disruption of the river's flow and function. Therefore, some of the Upstream Glonggong River segments need to be relocated so that the river's existence and function will not be disturbed. This research aims to find the best alternative in relocating the Upstream Glonggong River. The research method is carried out through hydrological and hydraulic calculations. The selection of relocation alternative of the Upstream Glonggong River was carried out using nine criteria weighting method. The selection criteria for river relocation alternatives used are: 1) upstream channel bottom elevation, 2) channel bottom width, 3) water level, 4) freeboard, 5) channel height, 6) gas plan facility elevation, 7) supporting buildings, and 8) mitigation and risk. The analysis result shows that the alternative selection analysis based on nine criteria assessment indicate that Alternative II (gas plan facility elevation +60.00 m, upstream channel bottom elevation +58.40 m, channel bottom width 6 m, drop structure, retention pond, and overflow) is the best relocation alternative of the Upstream Glonggong River for the construction plan of the gas plan facility in Jambaran Tiung Biru.

Study of Flow Characteristics Over a Rounded Edge Drop Structure in Open Channel

Flow over a drop structure is a form of free overfall called hydraulic drop. Hydraulic drop changes the nature of flow abruptly from sub-critical to super-critical condition. Rapidly varied flow analysis is a complex phenomenon and involves remarkable characteristics. Some of the drop structures constructed in Sindh and Punjab provinces of Pakistan had gone through diverse failures, consequential in interruption of water supply to irrigation fields encountering substantial economic loss. In the present study experiments were carried out in the hydraulic laboratory of Mehran University of Engineering and Technology on round edged drop structure fitted in a horizontal rectangular flume (channel model). Data regarding hydraulic drop and hydraulic jump characteristics were collected during the experiment. The observed data included: flow discharge (Q), radius of rounded edge drop structure (r), height of the structure (h), hydraulic drop length (Ld), hydraulic jump length (Lj), depth of flow at toe of the jump (Y1) and tailwater depth (Y2). Applying dimensional analysis, the non-dimensional parameters of the observed data were calculated. Using statistical analysis, empirical relationships among the non-dimensional parameters were established for the appropriate design of the drop structure. The research results showed that the length and depth indices are functions of D=q2gh3 and r/h values. It was also found that for rounded-edge drop structure, the length of the stilling basin (LSB) reduces as r/h ratio increases

A VORTEX DROP STRUCTURE AS DEAERATION SYSTEM FOR A SUBMARINE OUTFALL PIPELINE

Use of submarine outfall pipelines became more common since World Bank Group issued a new guideline for maximum emissions levels for thermal power plants in 1998 (van Dijk, 2005). The more restrictive levels for temperature increase at the receiving water, requires outfall systems to conduct the water down to greater depths to achieve the required dilution standard. However, air entrainment control into outfall pipes could be challenging, especially for discharges with high flowrates for which conventional deaeration chambers become too large. The problem could turn more difficult in coastal shelf areas at seismic zones, where the hydraulic height of the incoming flow must be effectively controlled and the design not only has to pursue hydraulic objectives but also stability requirements for these massive structures subjected to relevant seismic thrusts. A vortex drop structure was designed for the cooling water discharge system of a thermal power plant in Mejillones Bay, Chile. The structure addresses the elevation difference between the return flow pipe and the ocean outfall pipelines while adhering to the spatial restrictions at the project site. Energy dissipation as well as limitation of air entrainment into the outfall pipelines were critical design considerations. Tests where done on a 1:12.5 scale (Froude) physical model. Prototype structure is under construction. Operation is planned to start on mid-2018.