osInternational Journal of Civil Engineering and Technology (IJCIET) Volume 10, Issue 04, April 2019, pp. 2129-2140, Article ID: IJCIET_10_04_220 Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=04 ISSN Print: 0976-6308 and ISSN Online: 0976-6316 © IAEME Publication Scopus Indexed THE USE OF RETENTION POND TO PROTECT THE LAND FROM FLOODING IN LAMASI RIVER LUWU REGENCY SOUTH SULAWESI INDONESIA Ali Malombassi Doctoral Program in Environmental Science, Graduate School, Brawijaya University, Malang, Indonesia Pitojo Tri Juwono Faculty of Engineering, Brawijaya University, Malang, Indonesia Muhammad Bisri Faculty of Engineering, Brawijaya University, Malang, Indonesia Ratna Musa Faculty of Engineering, Indonesia Moslem University, Makassar, Indonesia ABSTRACT Luwu Regency, South Sulawesi Province is an area, encountering a lot of flood problems because in particular the rivers in downstream are relatively flat increase sedimentation in the lower reaches of the Lamasi River. In this study one of the rivers in Luwu district, which often experiences flooding every year and has a length of 76.43 km and an area of river basin 432.80 km2. The flooding caused losses of nine villages in the area surround the Lamasi river. The objective of this study is to determine the optimal capacity of the retention pond and the dimensions of the retention pool used based on the analysis using the Gumel and Nakayasu methods. The type of research based on the data is done by using a quantitative approach by collecting secondary data from the Central Office of the Pompengan and Jeneberang River Region in South Sulawesi province. The result showed that the optimal capacity of the retention pond is 1,600,000 m3 at 9.3 m elevation while the pool volume in the pond at the 10-year return period was 901,131.78 m3 and the water elevation in the pond is at plus 8.43 m. The dimensions of the retention pond are 3,069 m long and vary from 100 m to 300 m and within an average of 3 m, the height of the embankment is 1.50 m with the width of the embankment 5 m with an optimal reservoir of 1,500,000 m3. The age of the retention pool functions effectively because of the sedimentation of 4,481.01 m3 per year estimated for 133 years. \http://www.iaeme.com/IJCIET/index.asp 2129 editor@iaeme.com Ali Malombassi, Pitojo Tri Juwono, Muhammad Bisri and Ratna Musa Keywords: flood, reservoir, retention pond, river. Cite this Article: Ali Malombassi, Pitojo Tri Juwono, Muhammad Bisri and Ratna Musa, The Use of Retention Pond to Protect the Land From Flooding in Lamasi River Luwu Regency South Sulawesi Indonesia. International Journal of Civil Engineering and Technology, 10(04), 2019, pp. 2129-2140 http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=04 1. INTRODUCTION Flood is one of the disasters that often destruct various countries. Indonesia is one of the disaster-prone countries including floods. Regularly, Indonesia often experiences floods, earthquakes, landslides, cyclones, tornadoes and droughts. In the past decade, Indonesia often faces flooding every year in various cities [1,2]. The overall current flood disaster management may lead to more recurrent events and cause severe impacts. Sustainable actions are needed to solve these problems that include environment-based flood integrated countermeasures [3] Luwu Regency is located in South Sulawesi Province, Indonesia. This regency is often encountered with flooding problems because it is crossed by several river routes. Because of this process, the river channel in the downstream section has sand and clay material which is easily eroded and the river channel is easily moved during floods. Siltation of mud also the other problem along with the flood that lead to river capacity decreasing. The Lamasi River is one of the rivers in Luwu Regency which frequently causes flooding every year. The floods were often reported to have an environmental damage. The Regional Disaster Management Agency, Luwu Regency reported that in the Eastern Lamasi sub-district there were more than 9 flood points that cause environmental damages. Based on the field conditions in the Lamasi River, the flood control in accordance with the conditions of the field is chosen by the payment method using dead rivers as retention ponds. Retention ponds are an effective and general way of dealing with floods and can produce optimal solutions both from the cost and control the overall flood, besides the retention pool benefits from the others as follows: (1) The speed of the river flow can be increased so that erosion on river banks can be avoided; (2) The bottom sediments from upstream can be accommodated in the pond so that the bottom sediments are downstream; (3) Environmentally friendly because it does not damage the cliffs and trees on the edge of the river and asks for the quality of water downstream of the pond; (4) The retention pool that is designed does not fit the needs Debit flow from the pool must be owed because the discharge is the same as the capacity of the river so there is no overflow or flooding downstream of the pond [4]. The use of retention ponds has been carried out in various countries, such as Belgium [5], Scotland [6], Portugal [7] and Taiwan [8] to deal with flood and mud sedimentation. This pool is designed as a tub or pond that can hold or absorb water temporarily in it. The retention pond is divided into 2 types depending on the wall coating and the bottom of the pool, namely natural ponds and artificial ponds. Natural ponds are retention ponds in the form of basins or infiltration tanks that have been formed naturally and can be utilized either in their original conditions or made adjustments. Artificial ponds or non-natural ponds are retention ponds that are made deliberately designed with certain shapes and capacities at locations that have been planned in advance with stiff material layers, such as concrete. The retention pool referred to in flood control research is an artificial retention pool that has the following functions: 1) Replacing the role of recharge land that is used as closed land, housing, offices, then the recharge function can be replaced with a retention pool. The function of this pool is to collect http://www.iaeme.com/IJCIET/index.asp 2130 editor@iaeme.com The Use of Retention Pond to Protect the Land From Flooding in Lamasi River Luwu Regency South Sulawesi Indonesia direct rain water and flow from the system to be absorbed into the soil. So, this retention pool needs to be placed in the lowest part of the land. The number, volume, area and depth of this pool is very dependent on how much land is converted into residential areas. 2) As a controller that functions as a temporary shelter during the flood and the water is released and when the surface conditions on the river return to normal so that the peak of the flood can be reduced. There are three types of retention ponds, namely one retention pool next to the river, the two retention ponds are on the riverbank and the third is a retention pool elongated storage type. The three types of retention pools mentioned above are selected as the second type because they are in accordance with the conditions of the study area. The objective of this study is to determine the optimal capacity of the retention pond and the dimensions of the retention pool used based on the analysis using the Gumel and Nakayasu methods. 2. METHOD The study was conducted on the Lamasi river in Luwu district, South Sulawesi Province. The type of research based on data is done by using a quantitative approach by collecting secondary data from the Central Office of the Pompengan and Jeneberang River Region (COPJRR) in the form of topographic data, longitudinal and transverse river profiles and hydrological data. 2.1. Retention Pool Capacity The capacity of the retention pool can be optimized by taking into account factors such as hydrology and topography, to be able to clearly see the functions of the following: Hydrological analysis to determine the amount of the flood discharge plan will affect the amount of maximum discharge to be accommodated. Then in the above analysis, rainfall data are needed in all the regions concerned. Hydraulic analysis to determine the water level that will be accommodated and the capacity of the river downstream of the pool pond Plans for discharge and overflow door openings to maintain the stability of the water that comes out and keeps over topping the pond embankment if the incoming water discharge exceeds the planned discharge. Based on the things mentioned above, the capacity of the pool storage volume can be determined using the topographic map of the location of the pool that is equipped with elevation and contours using the general equation as follows: V = A. H (1) With A = the area of the reservoir and H = the depth in the pond, but in the implementation of this formula it cannot be used directly because of the uneven topographic conditions, so the calculation of the area of the pool is layered according to the height of the contour formula used as follows: A = (The upper area between the contour + The area under the contour) / 2 Hydrological Analysis Hydrological analysis aims to determine the amount of flood discharge based on debit records manually or automatically from AWLR (Automatic Water Level Record) or with empirical equations based on using rainfall data. The use of empirical formulas with rainfall can be done if data on recording debits is insufficient, or both methods are used to control each http://www.iaeme.com/IJCIET/index.asp 2131 editor@iaeme.com Ali Malombassi, Pitojo Tri Juwono, Muhammad Bisri and Ratna Musa other Determining the amount of river discharge based on rain needs to review the relationship between rain and river flow. The size of the river flow is largely determined by the amount of rain, rainfall intensity, area of the watershed, duration of rain, and characteristics of the flow area. Analysis of planned rainfall or frequency analysis was using the Gumbel and Log Pearson III method based on rainfall data obtained from the Central Office of the Jeneberang and Pompengan River Region. This office provided data from three stations namely, (1) Rante Damai (119 OP) rainfall recording station between 2000 – 2015; (2) Lamasi rainfall recording station (120 OP) between 2000– 2017; and (3) Makawa (51 H) rainfall recording station between 2000 – 2017. Table 1 The maximum daily rainfall at the three rainfall stations Year 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Maximum daily rainfall (mm) Batusitanduk Lamasi Rante Damai 100 250 95 115 145 95 120 70 96 200 193 95 120 100 95 134 177 160 130 129 95 80 106 95 125 94 99 75 86 98 55 98 99 70 131 99 50 125 90 92 92 95 50 135 38 50 107 36 39 81 39 61 - Average 148.33 118.33 95.33 162.67 105.00 157.00 118.00 93.67 106.00 86.33 84.00 100.00 88.33 93.00 74.33 64.33 60.00 50.00 Source: COPJRR 2) Distribution Suitability Test Calculation of rainfall plans with the two methods (Gumbel and Log Pearson Type III) above will give different results, so that results suitability tests are needed. Conformity test carried out by Chi-Square method (X2 - Test). The Chi-Square Compliance Test is a measure of the difference between the observed and expected frequencies. This test is used to test perpendicular deviation, which is determined by the formula: The testing steps are as follows: a. Plotting rain / debit data. b. Drag the line with the help of rain data points that have a certain return period. http://www.iaeme.com/IJCIET/index.asp 2132 editor@iaeme.com The Use of Retention Pond to Protect the Land From Flooding in Lamasi River Luwu Regency South Sulawesi Indonesia c. Price X2cr is searched from the table, by determining the level of significance (ïĄ) and the degree of freedom (DF), while the degrees of freedom can be calculated by the equation: Information: DF = degree of freedom n = Amount of data m = Number of parameters for X2cal (m taken 2). d. If the price of X2cal <X2cr (according to the table), it can be concluded that the deviations that occur are still within the permitted limits. Rainfall data from the Log Pearson III method and the Gumbel Method after being tested with Chi Squares are selected which have the smallest X2cal value. 3) Analysis of Flood Debit Plans The river drainage data required for the analysis of flood discharge are planned between the area of the Cacthman Area (Km2), the main river length L (Km), the elevation of the highest point Hmax / H2 (+ m), the lowest elevation of Hmin / H1 (+ m). needed. If viewed from the morphometry data of the watershed / watershed, the method of calculating the planned flood discharge from rainfall data can be used the hydrographic method in the Nakayasu synthesis unit and the Gamma my method because the river with analysis has a watershed area> 100 ha. Data on the characteristics of the Lamasi River Basin can be seen in table 2 below. Table 2 Characteristics of the Lamasi River Basin Characteristics Data Catchment Area 432.80 km2 Maximum height of river basin (H max) + 2,283.00 m Minimum height of river basin (H min) + 3.00 m 76.43 km Length of main river Source: Identification from topography map The selection of flood discharge flood discharge plan is based on the discharge of the analysis results from the above, then compared to the discharge originating from the results of recording the water level in the field. Debit analysis based on the recording of the face height uses the curvilinear method. The study discharge curve is used for analysis using Logarithmic motives, namely by taking debit Q1, and Q3 from curves made on logarithmic paper based on existing data and Q2 determined by formula: Q2 = (Q1 x Q3) 0.5 3 Then read on the curves of H1, H2 and H3 based on Q1, Q2 and Q3, then the curves are converted into a straight line by reducing or adding to the price of Ho obtained from the formula, đ»0 = đ»1+đ»2−đ»22 đ»1−đ»2−2đ»2 (2) Then the coefficients of K and n are determined by the formula, (ïy) – m log K – n (ïx) http://www.iaeme.com/IJCIET/index.asp =0 2133 (3) editor@iaeme.com Ali Malombassi, Pitojo Tri Juwono, Muhammad Bisri and Ratna Musa (ïxy) – (ïx) log K – n (ïx2) = 0 (4) And the relationship between Q and H is derived from the formula, Q = K (H – Ho)n (5) where : Q1, Q2 Q3 = water debit from existing data H1, H2, H3 = height of water taken from logarithmic curves based on Q Ho = water level that straightens the curve (ïy) = sum of log Q scores (ïx) =sum of log (H-Ho) scores (ïx2) = sum of x quadrate (ïxy) = sum of score x multiply by y M = number of data From the above equation, the amount of the debit (Q) can then be calculated for each record of water level (H), so that the average daily flow data of the river are obtained at the measurement location. While the maximum annual discharge is used to analyze the planned flood discharge. 3. RESULTS AND DISCUSSION 3.1. Frequency of Rainfall As mentioned above, the maximum daily rainfall data used in this analysis is data with the average method originating from three rainfall stations in table 1 using the Gumbel method and Log Pearson III and the analysis results as follows. The value of Rainfall in the two-year repetition period analyzed by the Gumbel method (96.70) was higher than that of the Log Pearson III method (73.38); while those in the reported period of 100 were higher in Log Pearson III (201.47) then in Gumbel (194.81) (Table 3). Table 3. Rainfall data Repeated with Gumbel and Log Pearson III No. Method 1 Gumbel Log Pearson III 2 2 96.70 5 122.96 Repeated periods (years) 10 20 25 140.35 157.04 162.33 73.38 96.49 125.34 143.00 164.02 50 178.63 100 194.81 178.86 201.47 3.2. Distribution Suitability Test Results with Chi Square Method Conformity Test Results Distribution with Chi Square Method Conformity test obtained differences found between the observed and expected frequency or must be X2cal <X2cr and the results of the analysis, showed the Gumbel method which has a difference X2cal with X2cr smaller than the Log Pearson III method, then the next analysis used the results of the Gumbel method frequency analysis. 3.3. Debit Plan http://www.iaeme.com/IJCIET/index.asp 2134 editor@iaeme.com The Use of Retention Pond to Protect the Land From Flooding in Lamasi River Luwu Regency South Sulawesi Indonesia The results of the planned discharge analysis or return period start 2, 5, 10, 25, 50 and 100 years with the Nakayasu and Gamma I methods. The result showed that Flood Discharge analysis with Gamma was always higher. It is projected to be 94.40 m3/second in the next 100 year (Table 4). Table 4 Flood Discharge Repeated Nakayasu and Gamma Methods Repeated periods 2 5 10 25 50 100 Projection of Flood Discharge (m³/second) Nakayasu Gamma 46.47 52.18 56.33 63.48 62.80 70.96 69.01 78.14 77.05 87.43 83.07 94.40 3.4. Debit Arch Debit curves were analyzed based on data recording of water level and discharge on the staff gauge on the Lamasi River (source data for the CPJRR) and described in the following graph, then regression of the relationship between water level and discharge obtained by the equation of discharge: Q = 8.553 (H --0.64)2.1 (8) Where H is the water level, then this equation is used to analyze daily debits based on recording water level. Figure 2. Relationship between debit and water level Daily debits obtained from equation 8 with a face height from recording the water level in the Lamasi river are then analyzed by the Gumbel method with the following results. The projection of water debit calculated by Gumbel Method was 44.83 m3/second in next 2 year and gradually increase to 88.70 m3/second in the next 100 year (Table 5). The maximum daily debit obtained from equation (8) with the height levelfrom recording water level in the Lamasi river was calculated. The result was showed in Table 5. Table 5. The Lamasi River Maximum Daily Debit No. Year Qmax (m3/sec) http://www.iaeme.com/IJCIET/index.asp No. 2135 Year Qmax (m3/sec) editor@iaeme.com Ali Malombassi, Pitojo Tri Juwono, Muhammad Bisri and Ratna Musa 1 2 3 4 5 6 7 8 9 1999 2000 2001 2002 2003 2004 2005 2006 2007 30.99 30.99 46.33 46.33 45.46 49.87 49.87 41.27 29.26 10 11 12 13 14 15 16 17 18 19 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 57.86 30.64 49.42 45.46 63.36 33.51 29.95 63.36 74.59 63.87 Furthermore, the discharge results in Table 5 above were analyzed with its frequency using the Gumbel method. The result was presented in Table 6. Table 6. Debit Calculation Results for Gumbel Method Repeat Repeated period 2 5 10 20 50 100 3 44.3 56.58 64.35 71.81 81.46 88.70 Debit (m /second) 3.5. Flood Debit Analysis Plan The planned flood discharge analysis is determined by comparing the Nakayasu method and the Gumbel method with the flood discharge resulting from recording in the river and then drawing the conclusion that the method closest to the recording discharge in the river will be used in subsequent planning. The results of the re-flow analysis in Table 3 compare with Table 5. It can be concluded that the results of Table 5 which approach table 3 are Nakayasu method analysis, so that the planned planning for retention pond optimization is used as a result of Nakayasu synthesis unit hydrographic method. 3.5. Optimization of Retention Pool Volume Optimization of the pool volume will be adjusted to the volume of water to be accommodated, in this study the planned flood discharge is used for a 10-year return period and the river discharge flow capacity in the downstream pond was 25 m3 / sec (source data for COPJRR). The amount of water to be accommodated in the retention pond was analyzed by Nakayasu synthesis unit hydrographic method and pool volume based on counts from the Lamasi river topography measurement data and the results of the analysis of the relationship between the water level and volume of retention ponds can be seen in Table 6 and then pond capacity calculated to obtain optimal storage. Figure 6 curvature of the basin showed that the optimal reservoir of 1,600,000 m3 in the elevation of the water is + 9.30 m. Table 7. Relationship between Elevation and Volume in the Retention Pool No. Elevation 1 2 3 4 5 4.00 4.50 5.00 5.50 6.00 Volume (m3) Wide m2 Perelev Total 0.00 1,370.73 8,217.24 37,397.35 46,195.60 0.00 0.00 4,793.99 22,807.30 41,796.48 0.00 0.00 4,793.99 27,601.28 69,397.76 http://www.iaeme.com/IJCIET/index.asp 2136 editor@iaeme.com The Use of Retention Pond to Protect the Land From Flooding in Lamasi River Luwu Regency South Sulawesi Indonesia 6 7 8 9 10 11 12 13 14 15 6.50 7.00 7.50 8.00 8.50 9.00 9.50 10.00 10.50 11.00 91,431.62 153,462.45 197,415.83 249,449.60 315,423.31 391,032.85 512,387.53 595,300.23 680,667.78 730,167.03 68,813.61 122,447.04 175,439.14 223,432.72 282,436.46 353,228.08 451,710.19 553,843.88 637,984.01 705,417.41 138,211.37 260,658.40 436,097.54 659,530.26 941,966.71 1,295,194.79 1,746,904.98 2,300,748.86 2,938,732.87 3,644,150.27 The volume that must be accommodated is analyzed based on the Nakayasu unit hydrograph in Q10 years, amounting to 901,131.78 m3 and water elevations in the pond at +8.43 m (pool bottom elevation +4.00 m). The results of the analysis of the volume contained in the pool each hour can be seen in tables and figures. The dimensions of the retention pool are 3,069 m in length, varying between 100 m to 300 m and in an average of 3 m, the height of the embankment is 1.50 m with the width of the embankment 5 m. The size of the retention pond depends on the flood discharge plan to increase the planned discharge, then the height of the water in the pond and the pool inundation area increases in this study the amount of the planned discharge being used for 10 years. This retention pool serves as a stabilizer to drain down water without exceeding the capacity of the river so that it does not occur or flood. In order to function properly this pool must be equipped with a release door for regulating the outflow and preventing the level of water bellow the maximum level. 800 700 600 Wide m2 (x 1000) 500 400 300 200 100 0 12.00 Elevation (M) 10.00 8.00 6.00 Volume Elevation Arch 4.00 Wide Elevation Arch 2.00 0.00 0 1,000 2,000 Volume m3 (x 3,000 4,000 1000) Figure 3. Retention pond capacity Table 8. Flood Volume Per Hour for 10 Years with the of the Nakayasu synthetic unit Hydrographic Method in the Retention Pool Time (hours) 0 1 Debit Discharge m3/second 10.56 12.49 Outflow m3/second 25.00 25.00 http://www.iaeme.com/IJCIET/index.asp 3 m /second 0.00 0.00 2137 Collected m3/hour 0.00 0.00 m3 0.00 0.00 editor@iaeme.com Ali Malombassi, Pitojo Tri Juwono, Muhammad Bisri and Ratna Musa 2 3 4 5 6 7 8 9 10 11 12 13 14 15 21.23 40.46 62.19 62.80 60.79 57.62 53.37 47.60 41.08 36.23 32.35 29.20 26.63 24.51 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 0.00 15.46 37.19 37.80 35.79 32.62 28.37 22.60 16.08 11.23 7.35 4.20 1.63 0.00 0.00 55,672.07 133,869.14 136,083.50 128,829.84 117,435.37 102,137.63 81,359.37 57,886.42 40,417.40 26,445.78 15,125.07 5,870.20 0.00 0.00 55,672.07 189,541.21 325,624.71 454,454.55 571,889.92 674,027.55 755,386.92 813,273.34 853,690.74 880,136.52 895,261.58 901,131.78 901,131.78 A previous study of flood design discharge at Bonai River, Kunto Darussalam Residence, Rokan Hulu Regency reported that the maximum discharge entering the maturity period for the 100-year return period was 224.401 m3/s. This method was used to analyze the Nakayasu synthetic hydrograph by rainfall units at Kampar Market Station in 2000 to 2009. Analysis using the Nakayasu synthetic hydrograph unit showed that there was rainfall with 100 years return period and produced a flow rate of 1,833,594 m3/s. Another study in the Upper Komering Basin showed that the peak discharge in several hydrographs methods are Nakayasu 607.32 m3/s [9]. 70.00 60.00 Flooding debit (m³/dtk) 50.00 40.00 Debit Keluar Outflow debit QTampung Q capacity 30.00 20.00 10.00 0.00 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Figure 3. Nakayasu synthetic unit hydrograph at Q10 One method that can be used to predict flood discharge is the basis of the hydrograph (Results from the Nakayasu synthetic unit hydrograph analysis at Q10 indicate that peak discharge at 3 hours, while capacity peak at 4 hours. Estimated flood discharge is needed to determine the optimal discharge size which is related to the dimensions and age of the structure being built in. The purpose of this estimation is to plan the optimal structure to overcome the flooding effectively and efficiently [10]. http://www.iaeme.com/IJCIET/index.asp 2138 editor@iaeme.com The Use of Retention Pond to Protect the Land From Flooding in Lamasi River Luwu Regency South Sulawesi Indonesia 3.6. Sedimentation The amount of sediment is calculated based on observations made by the water resources department, copyright works and spatial planning of the South Sulawesi Province on the Lamasi River, then a sedimentary curve is made between the Q discharge and the sediment discharge with a method similar to that used in making curves. Here was a picture of the curved sediment. 200.00 180.00 Sediment debit (Qs) ton/day 160.00 140.00 120.00 hasil Qs result 100.00 Qs Exist 80.00 60.00 40.00 20.00 0.00 0.00 10.00 20.00 30.00 40.00 50.00 60.00 Debit (Q) m3 /second Figure 5 Sediment Arch Based on the sedimentary curve above, a regression equation for the discharge relationship with sediment is obtained Q = 1.06 (H - 28.61)0.69 (9) The annual sediment rate can be calculated using the regression equation from the sediment curve above, the magnitude is as follows: 1) Average Sediment Production of 22.71 tons/day 2) If the sediment density is assumed to be 1.85t / m³, the sediment rate will be 7,725.25 tons / year or 4,481.01 m³/year for return of 133 years. 4. CONCLUSION 1. The planned flood discharge used in the planning of retention ponds is the result of 2. 3. 4. 5. analysis of the Nakayasu synthesis unit hydrograph method because the results are close to the discharge conditions of observations in the field. The optimal capacity of the retention pond is 1,600,000 m3 at 9.3 m elevation while the pool volume in the pond at the 10-year return period is only 901,131.78 m3 and the water elevation in the pond is at +8.43 m. Overflow elevation at + 8.43 m The dimensions of the retention pond are 3,069 m long and vary between 100 m to 300 m and in an average of 3 m, the height of the embankment is 1.50 m with the width of the embankment 5 m. The age of the retention pool functions effectively because of the sedimentation of 4,481.01 m3 / year so the effective age of the retention pond is projected for 133 years. 5. ACKNOWLEDGEMENTS The author would like to thank the Head of the Central Office of the Pompengan and Jeneberang River Region in South Sulawesi Province, the Rector of the Indonesia Moslem http://www.iaeme.com/IJCIET/index.asp 2139 editor@iaeme.com Ali Malombassi, Pitojo Tri Juwono, Muhammad Bisri and Ratna Musa University, and Dr. Amin Setyo Leksono, Brawijaya University who assisted in revising the initial manuscript. REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] Tse, C. W. Do Natural Disasters Really Lead to Forced Migration? Evidence from Indonesia in Proceeding of Northeast Universities Development Consortium Conference, New Heaven, USA, 2011. Centre for Research on the Epidemiology of Disasters (CRED). EM-DAT (The International Disaster Database) [online]. EMDAT, Brussels http://www.emdat.be/, 2014. Hapsari, R.I., and Zenurianto, M. View of Flood Disaster Management in Indonesia and the Key Solutions. American Journal of Engineering Research 5(3), 2016, pp. 140-151. 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Natakusumah, D., K., and Sabar, A. Determining Peak Discharge Factor Using Synthetic Unit Hydrograph Modelling (Case Study: Upper Komering South Sumatera, Indonesia), International Journal of Geomate, 13(36), 2017, pp.1-5. Tunas, G. I., Anwar, N., and Lasminto, U., the Improvement of Synthetic Unit Hydrograph Performance by Adjusting Model Parameters for Flood Prediction. International Journal of Engineering and Technology. 9, 2017, pp. 847-858. http://www.iaeme.com/IJCIET/index.asp 2140 editor@iaeme.com