Retention Basins Research Articles

Organic Removal Treatment Using Microbubble Generator (MBG) in Eutrophic Disorder Condition

The Techno Park basin, built as an extension of a small tributary of the Code River primarily acts as a retention basin for runoff during the rainy season. It improves the quality of water that has been degraded by domestic wastewater discharge from the surrounding community. Therefore, this study aims to assess the extent to which water quality of the basin can be improved with aeration technology. The aeration technology is a Microbubble Generator (MBG) built using a 100 Watts submersible pump with three horizontal nozzles at a depth of 40 cm from the water surface. Furthermore, the profiles of dissolved oxygen (DO) concentration were measured at the basin’s inlet and outlet, as well as the depths of 1 m below surface water and the bottom of the basin. Diurnal DO was measured to investigate the causes of supersaturation. The aeration performance was also determined from the COD parameters at the inlet and outlet. Discharge measurements were then conducted on the tributary/drainage channel to the inlet basin. The result showed that the DO supersaturation concentration has been attributed to the contribution of photosynthesis from phytoplankton such as algae. Furthermore, no change in DO concentration was observed in a range of 1 m depth from the surface of the water to the bottom (0.3 - 0.14 mg-DO/l). In this eutrophic state, DO increased exponentially during the daytime hours and then decreased during the night. The daily measurement showed an increase in the average DO of 2.31 mg/l (standard deviation of 1.56 mg/l), with average CODinlet fluctuations of 18.79 mg/l (standard deviation of 13.56 mg/l) and average CODoutlet of 14.38 mg/l (standard deviation 2.94 mg/l). Due to additional DO concentration coming from eutrophication during daylight, it was not possible to make a precise assessment of the effectiveness of the MBG aerator.

Citizens’ viewpoints on stormwater Beneficial Management Practices (BMPs) in Brazil

Floods are among the most dangerous and destructive hazards in the world. Stormwater Beneficial Management Practices (BMPs) are a set of strategies that can assist in reducing urban floods and their damages by capturing surface runoff and promoting infiltration. Engagement of citizens in the selection of stormwater BMPs may facilitate the decision-making processes and increase the chance of adopting and maintaining them. Due to existence of catastrophic floods in Brazil, implementing BMPs is essential in the urban areas. The objective of this study is to understand the viewpoints of citizens about a set of stormwater BMPs in Brazil. Moreover, we aim to comprehend whether diverging viewpoints about the BMPs can be associated with existence of different layers in the society. For this purpose, online surveys were used to access wide and diverse groups of citizens from different ages, levels of education and income, as well as geographical location. The questions and descriptions of BMPs were prepared in an accessible language, and then disseminated through various platforms. The responses of more than 1000 participants were analyzed using descriptive and statistical methods. Our results show that the participants found the retention and detention basins, as well as permeable pavement as the most efficient BMPs. Moreover, considering the small-scale practices, although lot related BMPs are considered less efficient, citizens are willing to use green roof, bioretention, and rain barrels in their properties. In addition, most of the respondents support public investments on stormwater BMPs. Our analyses show that participants' age and level of education statistically influenced their choice of BMPs and willingness to pay for their maintenance and construction. These results can help Brazilian policy makers to prepare flood management plans by including stormwater BMPs that would be more accepted by the population. In addition, proposing practices that are aligned with citizens’ perceptions creates a sense of responsibility, and is in accordance with the Brazilian New Framework of Sanitation that includes public participation in policy making.

Flood control strategy in kali sabi river basin in Tangerang

Tangerang has suffered from severe urban floods frequently. Flood control and management of the areas are needed to attain better social and economic rates, including to reduce damage to assets. This paper discusses some possible strategies of flood management systems and suggests the strategies that the government should apply in Kali Sabi river basin, Tangerang City. Deciding water retention as one of the best ways to be applied is begun with the study and survey on several parameters of hydrologic components including topography, watershed delineation, rainfall analysis, and possibility analysis and planning of the water management. The analysis results that the strategy to manage water stagnation is by constructing a retention basin. This area has a relatively flat topography and slightly high rainfall. However, there also has been an improper drainage system. These circumstances resulted in the area having a relatively long retention time on the ground. Based on several consideration strategies on flood management systems, a water retention basin is the best solution. Practically, the runoff water with a discharge of 158.44 m3/s causing flooding in the area could be accommodated by water retention construction.

House Price Capitalization of Stormwater Retention Basins: Evidence from Fresno-Clovis Metropolitan Area in California

House Price Capitalization of Stormwater Retention Basins: Evidence from Fresno-Clovis Metropolitan Area in California

Reviving Opportunities through Socio-Spatial Parameters for Community Interaction:

Within urbanized areas, the importance of neighborhood ponds should be assessed and investigated with its socio-spatial parameters (access and linkage, sociability, uses and activities, comfort and image etc) since such water bodies act as retention basin during floods, reservoir for lean period and responsive socializing agent to measure community interaction which are generally been neglected by city government, threatened by developers but taken care by neighborhood people in Old Dhaka. Most of the inner city small neighborhoods ponds have been encroached and filled up upon demand on land as the pond were not integrated in the city planning. The main objective of this research is to assess the significance of such water bodies and revive the spatial relationship of neighborhood ponds with its nearby residents. Therefore a socio-environmental survey (quantitative and qualitative) is held on neglected and threatened small neighborhood ponds of Old Dhaka with direct observation, in-depth interviews of the residents to compare the environmental, ecological and social contexts and explore the opportunities. An integrated assessment for enhancing sustainability and creating opportunities through community participation has been suggested to rejuvenate the ponds with attention for wetland preservation and to integrate into community development programs or planning.

Analysis of Farmers’ Perception and Attitudes of Water Quality in Margodadi Embung, South Lampung

Margodadi Embung (retention basin) is water pond that was designed for irrigation and conservation which is located in South Lampung, Indonesia. This Embung is surrounded through numerous farm fields, consisting of the cassava plant, corn plants, palm trees, and paddy fields. This research was aimed to know the farmers’ perception and attitudes of water quality in Margodadi Embung, South Lampung. Sampling was conducted using random sampling on farmers’ around the Embung, with the parameter of respondent profile, farming attitudes, knowledge about the Embung, and perception of the Embung water quality. The outcomes confirmed that the farmers had been using manure and chemical fertilizers for his or her fields, and also, they wiped clean their farm animals in Embung after plowing on the farm. Most of the farmers thought that the water quality is still good and fortunately, it was proved with the DO and BOD parameters that still be permitted according to Government Regulation no 82, 2001. However, it was indicated that the knowledge of the farmers of water quality will influence the perception and attitudes of the farmers towards the Margodadi Embung.

IDENTIFIKASI EFEKTIVITAS REAERASI MENGGUNAKAN MICROBUBBLE GENERATOR (MBG) PADA AIR EMBUNG

The retention basin at the Faculty of Engineering Gadjah Mada University was built as a flooding control into the Code river and improving the water quality. The water entering the basin, especially in the dry season, is characterized as greywater due to the dense settlements around the university. The purpose of this study was to determine the effectiveness of reaeration process using a Microbubble Generator (MBG) to increase DO, with the aim of this leading to an improved water quality. The MBG aerator with submersible pumps was installed at a depth of 40 cm from the water surface and placed in the middle of the pond. The aerator was permanently turned on. In situ monitoring of DO was carried out using a seri Lutron WA-2017SD DO meter. The increasing DO correlated with the changes of the surrounding weather which impact on water and air temperature. At the time of DO data collection, the water temperature ranged from 24.5oC - 27oC and the change in DO measured at the inlet and outlet of the reservoir was in the range 0.3 - 1.1 mg/l, with the DO directly surrounding the aerator reaching up to 2.4 mg/l from the inlet. With the DO increased, the concentration of pollutant organic loads can be reduced and the nitritation and nitratation processes has taken place properly so that it has reduced the pollutant load before the water enters the Code river.

Influence of a low-head dam on water quality of an urban river system

Dam removal in the United States is becoming a common practice for stream restoration as these structures age, climate driven precipitation patterns change, and ecological uplift becomes desirable. Yet in highly urbanized watersheds, these dams may operate as retention basins removing pollutants and mitigating hydrological change. While elimination may be ecologically and economically advantageous, sediment and pollutant removal processes may be better protective of water quality and damaging flooding. In Central Virginia, we compared a watershed split between an urbanized subwatershed (>20% impervious surface encompassing 37.8% of the total watershed land surface) flowing through a 18 Ha reservoir with a rural subwatershed (<5% impervious encompassing 63.2% of the total watershed land surface) located in the James River and Chesapeake Bay watersheds. This reservoir is scheduled for removal in the near future. Comparisons of data suggest that while portions of the urbanized watershed are degraded, this condition is not reflected at the confluence where water quality more closely resembles the rural and minimally impervious subwatershed. This conclusion was further strengthened from data collected following an unexpected dam overtopping in August 2018 where the reservoir was temporarily drained because of safety concerns. After the draining, water quality reversed with the confluence resembling the urbanized rather than the rural subwatershed. Most significantly, water quality flowing into the James River quickly and significantly shifted from a good to a degraded condition. This case study suggests reservoirs in highly urbanized watersheds may serve as critical water quality improvement structures and removal as part of a stream restoration strategy must be carefully considered.

Is flow control in a space-constrained drainage network effective? A performance assessment for combined sewer overflow reduction

Recurring combined sewer overflows (CSOs) can have a significant impact on the ecological condition of receiving water bodies. There are several structural measures, like adding retention basins and switching to low impact development solutions, that have been proposed to reduce the number of sewage overflows. Besides, several flow control strategies have been discussed in scientific literature that take advantage of the space within urban drainage networks, which is assumed to be adequate, for temporary storage. The adequacy of such storage space, however, is not a universally valid assumption as a large fraction of drainage networks frequently operate close to their design discharge. In this paper, we investigate the efficacy of flow control for a space-constrained drainage network. We employ a low-cost, heuristic real time control strategy with the use of flow control devices (FCDs) and available in-sewer space to reduce the magnitude of CSOs. We consider the performance of the proposed control strategy and discuss the effect of FCD location on CSO reduction. Our results, based on over 300 rainfall-event simulations, show that the flow control strategy using limited sewer capacity is more efficient during relatively small rainfall events, where the CSO is large enough to enable reduction using the chosen control rules. The CSO is reduced, to varying degrees, for around 80% of rainfall events with peak intensity between 10 and 20 mm h−1. For larger rainfall events, the flow control is more unstable in response to abrupt water release during control operation, which seems to be unavoidable because of the water accumulation effect and the transition to pressurized pipe flow in space-constrained networks. We also found that the flow control performance is highly sensitive to the FCD location – as it depends on the interplay of the peak rainfall intensity and the water level condition immediately upstream of the FCD. The efficacy of a location for flow control is determined by the unfilled capacity (i.e., effective in-sewer storage potential) in the pipe upstream of the FCD during the rainfall peak; furthermore, the location also has to be resistant to the water accumulation effect. Using our analysis, we substantiate two anticipated caveats to flow control strategies when the storage space is limited in a drainage network: diminished performance in CSO reduction and the appearance of additional control-related challenges, which are otherwise mitigated in more spacious networks.

Morphological and molecular characters of Cherax quadricarinatus (von Martens, 1868) from Sermo Reservoir and Tambakboyo Retention Basin, Daerah Istimewa Yogyakarta, Indonesia

The Australian red claw freshwater crayfish, Cherax quadricarinatus is one of the most widely distributed and cultivated freshwater crayfish due to its high tolerance towards various environmental conditions. Native to North Australia and South Papua New Guinea, this crayfish was found in Tambakboyo Retention Basin in 2016 and Sermo Reservoir in 2019. This research was aimed to identify the morphological and molecular characters of C. quadricarinatus collected from Sermo Reservoir and Tambakboyo Retention Basin, Yogyakarta. The genetic information of the samples was compared to Australian red claw freshwater crayfish currently available. The methodology used for this research are morphological, morphometrical, meristic identification, and molecular identification using the PCR method. The primer used to be 1471 primers as the forward primer and 1472 primers as the reverse primer. In conclusion, all six specimens obtained were identified to be C. quadricarinatus. Morphological analysis using UPGMA showed that all specimens were formed one big cluster and has the highest similarity index (1.00). Molecular analysis using BLAST showed that specimen from Sermo Reservoir was 98.96% identical to C. quadricarinatus and specimen from Tambakboyo Retention Basin was 100% identical to C. quadricarinatus. Thus concluding that based on their morphological and molecular character, all samples of this study were C. quadricarinatus. This finding also contributes to the distribution information of C. quadricarinatus in Daerah Istimewa Yogyakarta

Hydrological Modeling of Green Infrastructure to Quantify Its Effect on Flood Mitigation and Water Availability in the High School Watershed in Tucson, AZ

Green Infrastructure (GI) practices are being implemented in numerous cities to tackle stormwater management issues and achieve co-benefits such as mitigating heat island effects and air pollution, as well as water augmentation, health, and economic benefits. Tucson, Arizona is a fast-growing city in the semiarid region of the southwest United States and provides a unique landscape in terms of urban hydrology and stormwater management, where stormwater is routed along the streets to the nearest ephemeral washes. Local organizations have implemented various GI practices, such as curb cuts, traffic chicanes, roof runoff harvesting, and retention basins, to capture the excess runoff and utilize it on-site. This study models the 3.31 km2 High School watershed in central Tucson using the Automated Geospatial Watershed Assessment (AGWA) tool and the Kinematic Runoff and Erosion (KINEROS2) model. Each parcel in the watershed was individually represented using the KINEROS2 Urban element to simulate small-scale flow-on/flow-off processes. Seven different configurations of GI implementation were simulated using design storms, and we stochastically generated 20 years of precipitation data to understand the effects of GI implementation on flood mitigation and long-term water availability, respectively. The design storm analysis indicates that the configuration designed to mimic the current level of GI implementation, which includes 175 on-street basins and 37 roof runoff harvesting cisterns, has minimum (&lt;2%) influence on runoff volume. Furthermore, the analysis showed that the current level of GI implementation caused an increase (&lt;1%) in peak flows at the watershed outlet but predicted reduced on-street accumulated volumes (&gt;25%) and increased water availability via GI capture and infiltration. When the GI implementation was increased by a factor of two and five, a larger reduction of peak flow (&lt;8% and &lt;22%, respectively) and volume (&lt;3% and &lt;8%, respectively) was simulated at the watershed outlet. The 20-year analysis showed that parcels with roof runoff harvesting cisterns were able to meet their landscape irrigation demands throughout the year, except for the dry months of May and June. Additionally, stormwater captured and infiltrated by the on-street basins could support xeric vegetation for most of the year, except June, where the water demand exceeded volume of water infiltrated in the basins. The current level of GI implementation in the High School watershed may not have significant large-scale impacts, but it provides numerous benefits at the parcel, street, and small neighborhood scales.

The effects of sediment traps on instream habitat and macroinvertebrates of mountain streams

Sediment transport in mountain streams can be a major hazard to downstream infrastructure. Consequently, sediment traps are a common feature in many high gradient streams to retain large volumes of sediment and protect settlements from major sediment transport events. Despite the wide application of these instream structures, there is little knowledge regarding the environmental and ecological effects on streams. Here, we investigated the hydromorphological effects of sediment traps on instream habitats and associated macroinvertebrate communities in four impacted and three non-impacted streams in Switzerland. Sediment traps significantly disrupted the sediment regime homogenising grain size percentiles compared to the natural stepwise downstream fining in control streams. This disruption in the sediment regime resulted in finer grain size distributions upstream of the sediment trap, and reduced substrate diversity in the sediment retention basin and just downstream of the trap. The reductions in substrate diversity resulted in an altered macroinvertebrate community composition. Further, the disconnection in sediment transport led to a lack of longitudinal correlation in macroinvertebrate communities. Refugia provision downstream of the sediment trap, and resource availability within the retention basin, were diminished, potentially reducing resilience of macroinvertebrate assemblages to instream disturbances. The effects of sediment traps were most likely localised in three of the four streams with substrate diversity recovering to comparable control values within 8 wetted widths (ca. 50 m) downstream of the trap associated with natural longitudinal fining. In contrast, ecological and environmental effects propagated downstream in one impacted stream with no recovery being evident. Sediment retention basins in the impacted streams provided a local artificially unique habitat of dynamic-braided channels. Our results indicate that sediment traps can significantly disrupt the sediment regime with important consequences for instream ecology and environmental conditions, although these effects can be system specific. Further work is needed to fully understand the effects of sediment traps in mountain streams to assist resource managers in the mitigation and future construction of these structures.

Uzbekistan’s Aquatic Environment and Water Management as an Area of Interest for Hydrology and Thematic Tourism

The functioning of Uzbekistan’s economy is closely linked to the water resources of its huge cross-border rivers: the Amu Darya and the Syr Darya, as well as to the groundwater present within their basins. Both natural lakes and artificial reservoirs (e.g. the Aydar-Arnasay system of lakes, the Kayrakkum Reservoir, the Chardarya Reservoir) are present there, which retain significant amounts of water, and large canals with lengths of up to several hundred kilometres which involve complex hydraulic structures are used for irrigation purposes. All these are components of a water management system which needs optimisation; as much as 80% of agricultural land is irrigated, with 70% of the water being lost due to inefficient irrigation systems. The consequence of this allocation of river flows and the overuse of water in irrigation systems has been the disappearance of the Aral Sea (1960 year – 68,900 km2, 2017 year – 8,600 km2) and the inflow of water into the Sarygamysh Lake as well as the reduction of Uzbekistan’s groundwater resources by about 40%. The intensive development of irrigated agriculture is associated with changes in surface and groundwater quality caused, inter alia, by the increased use of chemicals in agriculture and the discharge of collector-drainage waters into river systems as well as their reuse. The extent of environmental degradation in some areas (especially in the Aral Sea region) is unique on a global scale. The origins of Uzbekistan’s other hydrological tourist attractions are related to attempts to ensure the availability of water for both human consumption and industrial use under conditions of water scarcity in the country’s arid and semi-arid climates. Not just the spectacular watercourses and water bodies present there (e.g. rivers, lakes, canals), but also small water retention facilities and minor infrastructure elements (e.g. wells, springs and retention basins, canals, ditches and flow control structures) are of potential tourist importance.

Diversity of cyanobacteria from thermal muds (Balaruc-Les-Bains, France) with the description of Pseudochroococcus coutei gen. nov., sp. nov.

Cyanobacteria are able to synthesize a high diversity of natural compounds that account for their success in the colonization of a variety of ecological niches. Many of them have beneficial properties. The mud from the thermal baths of Balaruc-Les-Bains, one of the oldest thermal baths in France, has long been recognized as a healing treatment for arthro-rheumatic diseases. To characterize the cyanobacteria living in these muds, several strains were isolated from the water column and biofilms of the retention basin and analyzed using a polyphasic approach. Morphological, ultrastructural and molecular (16S rRNA gene and 16S-23S ITS region sequencing) methods were employed to identify nine cyanobacterial strains belonging to the orders Chroococcales, Synechococcales, Oscillatoriales and Nostocales. The combination of morphological and genetic characteristics supported the description of a new genus and species with the type species as Pseudochroococcus coutei. The taxonomic diversity in the muds from Thermes de Balaruc-Les-Bains appears higher than previously documented, providing new candidate taxa for their observed therapeutic properties.

SIMULASI POLA OPERASI EMBUNG SERBAGUNA TAMBAKSARI KABUPATEN CILACAP DENGAN METODE STANDARD OPERATING RULE (SOR)

Abstract Human survival depends on water availability as water is a basic needs. As population increases, water becomes more limited. One of the ways to prevent draught is collecting water in retention basin. Tambaksari Multipurpose Retention Basin serves to provide basic water demand and irrigation water for the local community. Water availability and water demand should be equal, so a simulation of the operating patter of the retention basin is necessary to distribute water equally and determining the failure level of the retention basin in performing its task. In the present study, the retention basin operating pattern was simulated using Standard Operating Rule (SOR) method. The present study used secondary data, including population data, rainfall data, climatological data and technical data of the retention basin. The size of DAS Tambaksari is 0.41 km² while the size of the irrigated land is 12 Ha. The rainfall data was from 2008-2018 obtained from two rain stations, population data of Tambaksari Village was from 2008-2019, and the climatological data was from 2014-2019. The simulation result of the retention basin operating pattern using SOR method showed that the final collection wasn’t under minimum collection and failure happened in the operation of the retention basin for one year. . The optimal ability of the target release is 70.83% for the reliability of irrigation needs and the level of reliability for raw water needs of 58.33%. Population projection analysis to determine the population in 20 years showed that the future population of 4044 required 3.861 l/person/s of water. Irrigation demands for rice-rice-palawija planting pattern showed that irrigation intake was 11.89 l/s. Water balance determined the balance between inflow and outflow. The value for average water availability was 0.021 m³/s while total average water demand was 0.016 m³/s. therefore, the water availability in partial intake wasn’t able to meet the irrigation and basic water demands. Keywords: discharge, retention basin operation simulation, SOR

The landlords, the peasant, and the retention basin: Local political ecology of water management in the small island of Semau, Kupang, Indonesia

Abstract. Kuswardono PT, Mudita IW, Pandie DBW. 2021. The landlords, the peasant, and the retention basin: Local political ecology of water management in the small island of Semau, Kupang, Indonesia. Intl J Trop Drylands 5: 12-19. Freshwater is the most fundamental issue in small islands because of very small catchment area and low water retention capacity. To ensure water availability for domestic and agriculture purposes, the Government of Indonesia (GoI) has built hundreds of retention basins in all islands in East Nusa Tenggara Province from 1985 until recent times. In the small island of Semau where the study is undertaken, the availability of more than 24 retention basins did not solve freshwater problem. Inequality of distribution and usage of water from retention basin has become latent issues for more than 20 years. Under water provision program of GoI, all small retention basin management has been handed over to local community to become common pool resources (CPR). However, retention basin as CPR is not happening as expected. Using the Social-Ecological System Framework (SESF), the study found that one of the Governance components of SESF, i.e. property rights, is the key problem in achieving CPR. Informants from 5 villages interviewed and involved in focused group discussions consistently mentioned the word landlord in stories of water conflict, sabotage, and exclusion of access to water. The word landlord implied a tenurial or property rights system. A landlord had the traditional rights as a land custodian of the retention basin and all resources on his lands. The findings suggested that further investigation of the tenurial system and its transformation is needed whenever a vital construction such as retention basins would occur. In the past, the landlord would wisely distribute land and water as social goods so each person living in his ancestral land would not suffer from hunger. The construction of new retention basins could transform the roles of a landlord from a land custodian into a land owner and transform common-pool resources into private goods.

Modelling of sediment supply from torrent catchments in the Western Alps using the sediment contributing area (SCA) approach

AbstractThe production of coarse sediment in mountain landscapes depends mainly on the type and activity of geomorphic processes and topographic and natural conditions (e.g. vegetation cover) of these catchments. The supply of sediment from these slopes to mountain streams and its subsequent transport lead to sediment connectivity, which describes the integrated coupled state of these systems. Studies from the Northern Calcareous Alps show that the size of the sediment contributing area (SCA), a subset of the drainage area that effectively delivers sediment to the channel network, can be used as a predictor of sediment delivery to mountain streams. The SCA concept is delineated on a digital elevation model (DEM) using a set of rules related to the steepness and length of slopes directly adjacent to the channel network, the gradient of the latter and the vegetation cover. The present study investigates the applicability of this concept to the Western Alps to identify geomorphologically active areas and to estimate mean annual sediment yield (SY) in mainly debris‐flow‐prone catchments. We use a statistical approach that shows a parameter optimisation and a linear regression of SY on SCA extent. We use a dataset of ~25 years of assessed coarse sediment accumulation in 35 sediment retention basins. In the investigated catchments, sediment transport is governed by several factors, mainly by the extent of vegetation‐free areas with a minimum slope of 23° that is coupled to the channel network with a very low gradient of the latter. With our improved framework, we can show that the SCA approach can be applied to catchments that are widely distributed, in a large spatial scale (hectare area) and very heterogeneous in their properties. In general, the investigated catchments show high connectivity, resulting in significant correlations between long‐term average yield and the size of the SCA.

Cost Analysis of Green Infrastructure Compared to Conventional Stormwater Storage

Low Impact Development (LID), or green infrastructure, refers to a land planning and engineering design practice to address urban storm runoff. The nature of LID is to mimic the pre-development environment to retain runoff through infiltration, retention, and evaporation. Despite the fact that numerous studies have analyzed the performance of runoff volume reduction and peak flow of various green infrastructures, little is known regarding the economic benefits of adopting LID practices. In this research, three completed construction projects in the Phoenix, Arizona metropolitan area were selected to perform an alternative LID design including extensive green roof (GR) and permeable interlocking concrete pavement (PICP), to determine the cost effectiveness of using LID to reduce the use of a conventional stormwater storage system. A life cycle cost (LCC) analysis was conducted to better understand the cost benefits of applying LID to meet current drainage design criteria as per the project requirements. The results found that applying LID resulted in an average LCC saving rate of 23% compared to a conventional stormwater storage system over a 50 year service life and 15.1% over a full LID (GR+PICP) strategy. Furthermore, it was discovered that LID has little cost savings benefits when constructing above-ground retention basins due to cheaper associated construction costs.

Analisis Kapasitas Kolam Retensi Untuk Pengendalian Banjir di DAS Buah Kota Palembang

According to Public Works Office of Palembang City, Buah Watershed is listed as one of priority areas that requires immediate flood management actions. Flat terrain, high rainfall intensity, tidal fluctuation worsens by massive land use change, are major causes that increase surface water runoff. Therefore, retention basins as one of technical solutions are expected to accommodate runoff discharge and reduce flood. This study aims to analyze the existing hydrological conditions of Buah watershed and to simulate the effectiveness of designed retention basins on peak flow reduction. Hydrological analysis using SCS Unit Hydrograph Model, HEC-HMS combine with spatial analysis using GIS in 26 subcatchment areas resulted on peak discharges range from 1,27 m3/s – 15,71 m3/s. Furthermore, there are ​​12 proposed retention basins within study area ranges from ​​0,580 Ha – 3,967 Ha that are designed to reduce the peak discharge. Simulation result of flood discharge reduction using HEC-HMS indicates that the effectiveness of retention basins in proposed locations varies from 0,03% - 80,05% depending on watershed areas, land availability, and the depth of retention basins.

Evaluasi dan Analisis Kolam Retensi Pengendalian Banjir: Studi Kasus Kolam Retensi Brimob Kota Palembang

Brimob retention basin located within the Sekanak Sub-watershed system, which is a flood-prone point. Administratively, the Brimob retention basin area is a part of the Sub-district of Ilir Barat I. The research method used is computer modeling. The steps taken are: data collection, hydrological analysis, cross-sectional analysis, hydrological and hydraulic modeling using pumps. The Brimob retention basin can accommodate a volume of water up to 115,103.73 m3, up to an elevation of the embankment of + 4.30 m. The magnitude of designed rainfall is R2 = 118.78 mm, R5 = 144.78 mm, R10 = 161.99 mm and R25 = 183.73 mm. The peak discharge of each return period is Q2 = 6.30 m3 / s, Q5 = 7.67 m3/s, Q10 = 8.59 m3/s and Q25 = 9.74 m3/s. To assess the effectiveness of pump operation, 2 (two) pumping capacities are simulated, namely: 250 l / sec and 500 l / sec, each used 2 (two) pump units. The simulation used a pump with a capacity of 500 l / sec, and the amount of discharge (inflow) for each return period is as input. The conclusion is that the use of a pump with a capacity of 500 l / sec can overcome excess water volume and avoid runoff and effective in dealing with the excess water in the Brimob retention basin.