N The Study on Countermeasures for Sedimentaion in The Wonogiri Multipurpose Dam Reservoir in The Republic of Indonesia Workshop IV, Surakarta, January 18, 27 Master Plan on Sustainable Management of Wonogiri Reservoir N Present Sediment Discharge at Babat Barrage BENGAWAN SOLO 22.9 million m3/year Sediment Discharge from Wonogiri Increase of sediment to be.8 million m3/year discharge to Solo River estuary will SCALE be approx. 5% 15 3 45 6 75 9 km Flushing Mitigation Measures of Impacts Basic Policy To minimize the Impact to the d/s by careful gate operation Combined operation BENGAWAN between SOLO Wonogiri Dam and Colo Weir Monitoring in downstream reaches SCALE 15 3 45 6 75 9 km Q, Turbidity (Ex.) Operation Rule Allowable limit of concentration & duration shall be defined Operable period shall be strictly prohibited in dry season Thank You very much for Your Kind Attention! Japan International Cooperation Agency JICA Ministry of Public Works The Republic of Indonesia Nippon Koei Co. Ltd. and Yachiyo Engineering Co. Ltd. Page / 6
Estimating sediment volume into Brantas River after eruption of Kelud volcano on 199 Mr. Takeshi Shimizu National Institute for Land and Infrastructure Management
IEstimating Sediment volume into Brantas River after eruption of Kelud Voncano on 199 Takeshi SHIMIZU 1, Nobutomo OSANAI 1 and Hideyuki ITOU 1 1 National Institute for Land and Infrastructure Management, Ministry of Land, Infrastructure and Transport, Japan The Brantas River that flows through East Java Province, the Republic of Indonesia, is the second largest river. It has 11,8km 2 catchment areas and total length of the river approximately 32km. The Brantas River Basin has been developed based on the 1 st to 4 th master plans since the Second World War. The purpose of master plans was mainly dam constructions in the middle stream and upstream for flood control, water supply for agricultural and industrial use, and electricity generation. The each plan was almost successfully completed. In the Brantas River Basin, several active volcanoes located, originally sediment production is intense. The Brantas River Basin now has two serious water and sediment related problems as followed as bellows. (a) The decrease of reservoir s effective capacity due to sediment inflow to the reservoirs in the middle stream and upstream. (b) The riverbed degradation due to sand mining in the lower stream. Related to the decrease of reservoir s effective capacity, a total annual average 3 million m 3 of sediment has flowed into reservoirs, and already filled approximately 43% of the reservoirs in 23. The riverbed degradation has increased the risk of damage such as the flood disasters, lateral erosion, and constructions flow out. The main factor of the riverbed degradation is considered sand mining. More than 4 million m 3 of sediment were excavated from the river bed in 2. Moreover, volcanic materials supply due to the eruption sometimes gives additional effect along the basin. Especially Kelud volcano (elevation: 1,731m) indicates high activity; it might give serious effects to the basin. The aim of this study is to estimating the sediment volume into Brantas River Basin after Kelud volcano eruption on 199 using numerical simulation. Keywords: Water and Sediment Management, Brantas river, volcanic eruption
Estimating sediment volume into Brantas River after eruption of Kelud volcano on 199 SHIMIZU Takeshi, OSANAI Nobutomo and KOGA Shozo Erosion and Sediment Control Division, Nation Institute for Land and Infrastructure Management Investigation Area > Brantas River(basin area : 11,8 km 2, river length : 32 km ) is located on the Island of Java, Indonesia. >There are active volcanoes such as Kelud. > Development plan of the Brantas river basin have started since 1959. A lot of water facilities including reservoirs were constructed in the projects. Kelud Volcano Kelut Volcano Surabaya The 2 nd International Workshop on Water and Sediment Management Malang, Indonesia 22-23 November, 27, Location map of investigation area History of development in Brantas River Basin There are 4 master plan executed in the Brantas River Basin GDP Paddy field Agriculture Industry GDP 1st 2nd 3rd 4th Paddy production Paddy field area Background of this study Problem 1 Riverbed degradation caused by sand mining Eruption of Kelud volcano is thought to be one of the biggest factors to makeing serious effect on both problems > Time going, economic factors increasing > The master plans were effective. But another problem occurs > For example sedimentation in dam reservoirs and river bed degradation population Storage Problem 2 Dam sedimentation For the water resources management in the Brantas river basin, it is important to clarify the effect of volcano-crust for the river. The purpose of this study To clarify the effect of Volcanic activities on sediment conditions in Brantas Rivers Authors carried out numerical analysis applied to Kelut volcano eruption on 199. Volcanic Activities of Kelud Volcano > Kelud volcano ( 1,731m height ) is one of the high level active volcano located in Java Island. > It has 4 eruptions records since 1919. > Almost all of the scale of eruptions were VEI 3 > In each event, following phenomenon also occurred: 1) Lahar due to Phreatic explosion. 2) Plinian with pylocrastic flow 3) Lahar due to the breach of crater lake Table : scale of eruption of Mt. Kelud since 1919. 1
The latest eruption of active volcano,kelud Numerical simulation carried out in this study Considering the types of Kelud volcano eruption, we carried out following simulations to Kelut volcano eruption on 199. Jawa Pos, 21 st of Nov. 27 > Lahar due to crater wall collapsed type simulaiton(2-d analysis) > Pyroclastic flow simiulation( 2-D analysis) > Pumice fall distribution calculation(1-d analysis) Jawa Pos, 5 th of Nov. 27 Simulation model for lahar This calculation assumes that crater wall collapse triggering lahars. Input of Hydrograph We calculate the hydrograph according to the volume of crater lake on 199 eruption. Red relief map around crater of Kelut volcano Total discharge of Water is about 4,, m3 Sediment supplied by M.P.M formula Discharge(m3/s) Time(s) Relationship between time and discharge Results of lahar calculation minutes Kilometers Kilometers Arrival time distribution of Lahar Distribution of depth of the flow 2
This figure shows sediment volume inflows into Brantas River within about 3 hours. So the more time going, the more volume flows into Brantas River. Kilometers Distribution of sediment depth after lahar flow down According to these figures, almost all of water and sediment from crater lake flows into Brantas River Basin. Total volume of water is about 4 million m3 in this case. So, Lahar has serious effect on the conditions of Brantas River. Simulation model for pyroclastic flow Result of calculation of pyroclastic flow Pyroclastic flow divided to two layers; Surge and main body. Main body is dragged to surge. So, it is important to know the behavior of main body. hours We followed Yamashita & Miyamoto(1991) s model in which the main body behavior is treated as the dry particle flow. Schematic model of a pyroclastic flow Distribution of arrival time of pyroclastic flow Kilometers Distribution of pyroclastic thickness of deposition Numerical analysis model of pumice fall distribution This results show Pyroclastic flow doesn't have serious effect on Brantas River in short term. But pyroclastic flow supplies hillside area with a lot of unstable sediments. So, In the long term, it becomes high potential to make debris flow or lahar generate as the secondary disasters. It is difficult to model behavior of pumice fall precisely, because pumice fall has complex factors to simulate. We use the geometrical model following Miyamoto(1993). Schematic model of volcanic plume Distribution of pumice fall is calculated by hight of plumes and wind direction. 3
Result of calculation of pumice fall distribution A lot of pumice fall does not directly fall in the Brantas River. 1 cm 5 cm Distribution of pumice fall is determined by wind direction. In Brantas River Basin, everywhere is possible to damage by pumice fall. But After the heavy rainfall, pumice fall is possible to flow down, changing forms to concentrated flow. Because gradient of hillside over a wide range on Kelud volcano is greater than 2 degree. Distribution of gradient more than 2 degree about Kelud volcano Summary and conclusion Lahar reach the main river course. Lahar is possible to make severe impact on the sediment conditions in Brantas river basin. Pyroclastic flow does not reach the main course. However unstable sediment on the mountain slope is increased, so that the sediment yield will be increased. Pumice fall reach the main river course. But in short term the effect on changing sediment condition in Brantas River Basin is not so large. But pumice fall yields unstable sediments in Brantas River Basin. Summary and conclusion We can recognize the impact of eruptions on the river is not so big in short term. But it is considered the potential of sediment movement is increased after eruptions. Because these sediment is easy to move if heavy rain falls. Future studies of our plan Lower Reach How much volume of sediment from upper reach is necessary for lower reach to become equilibrium river bed condition??? Upper Reach After the execution of the previous simulation, We estimate how much volume of sediment is necessary for lower reach. Then we can consider how much volume is allowed to flow down into dam reservoirs from upper reach. River bed degradation by sand mining We have plans to execute simulation of the river bed variation; case 1) in normal condition. case 2) in volcanic activities took place. -> results of this presentation is preliminary studies for case 2) 4
Thank you! Terima kasih! 5
A Bed-Porosity Variation Model - as a tool for integrated sediment management- Prof. Masaharu Fujita DPRI, Kyoto University
A Bed-Porosity Variation Model - As a tool for integrated sediment management - Masaharu FUJITA 1, Muhammad Sulaiman 2 and Daizo Tsutsumi 1 1 Disaster Prevention Research Institute, Kyoto University 2 Graduate School of Engineering, Kyoto University Keywords: bed variation, porosity, grain size distribution, sediment management, Talbot distribution, As the void of bed material plays an important role in fluvial geomorphology, infiltration system in riverbeds and river ecosystem, a structural change of the void with bed variation is one of the concerned issues in river management as well as bed variation. Thus, a bed-porosity variation model is strongly required and it is expected that such a model contributes the analysis of those problems as a tool for integrated sediment management. A flow chart of the presented numerical simulation of bed and porosity variation is shown in Fig.1. As the porosity is one of the variables in this model, we must solve the following equation as a continuity equation of sediment. t z z o 1 Q (1) B x s 1 dz Input data Flow analysis Temporal analysis of change of grain size distribution and porosity Bed variation analysis Identification of grain size distribution type Geometric parameters of grain size distribution Analysis of change of grain size distribution and porosity Estimation of the porosity Fig. 1 Flow chart of the presented bed-porosity variation model
where = porosity of bed material, z = bed level, z o = a reference level, Q s = sediment discharge and B=channel width. Porosity is dependent on the grain size distribution of bed material and its compaction degree. In this paper, the compaction degree is considered empirically and the porosity is assumed to be a function of geometric parameters of grain size distribution. f n 1, 2, 3,... (2) where 1, 2, 3.= geometric parameters of grain size distribution. As we assume that the porosity is not constant depending only on the grain size distribution, the time differential term on porosity can not be neglected in Eq.(1). According to the previous exchange model between bed material and transported sediment such as Hirano s model, the change of grain size distribution in a time interval cannot be obtained without the change in bed elevation in the time interval. This means that Eq.(1) is an explicit equation. For this problem, we obtain temporally the change in the grain size distribution in the original mixing layer and then calculate the change in bed elevation using the temporal grain size distribution as shown in Fig.1. There are some types of grain size distribution such as lognormal distribution and Talbot distribution. Therefore, we need a method for identifying the distribution type and obtaining the relation between the geometric parameters and the porosity for each type. For example, lognormal distribution has a parameter of and Talbot distribution has two parameters of d max /d min, n t, where =standard deviation of lnd, d max =maximum grain size, d min =minimum grain size and n t =Talbot number. A type of grain size distribution can be identified visually by the shape of grain size distribution and the probability density distribution. However, this visual identification method is not available for riverbed variation models. Thus, Sulaiman et al. (27a) have introduced the geometric indices and to identify the distribution type. The indices and are defined as Eq.(3) and Eq.(4) respectively, designating the relative locations of the grain size d peak for the peak probability density and the median grain size d 5 between the minimum size d min and the maximum size d max. logd max peak (3) logd max logd logd min 1..5 Border-3 Border-2 M1 Talbot Area. Line-1..5 1. log d log d Lognormal Area max 5 (4) max AT1 AT2 AT3 AT4 Anti-Talbot Area log d log d Line-2 P2 P1 LN Q1 Q2 M2 M3 B1 B3 D3 D2 D1 T4 T3 T2 T1 C1 C2 C3 B2 N1 min N2 N3 Border-1 Border-4 Fig.2 Diagram indicating Talbot, anti-talbot and lognormal region
The indices of Talbot and anti-talbot distributions are on Line-1 (= and <<.5) and Line-2 (=1. and.5<<1.) in Fig.2. The indices of lognormal distribution are plotted just on the center point (.5,.5). The indices of the other distribution are plotted on the area of <<1 and <<1, apart from Line-1, Line-2 and the center point. However, there is an area where no unimodal distribution exists. From a geometric analysis, an area where unimodal distribution exists is surrounded by Border-1, Border-2, = and =1. as shown in Fig.2. It seems reasonable that the grain size distribution type is identified with the distance to the point (, ) from Line-1, Line-2 or the center point. According to this criterion, the border line between Talbot distribution and lognormal distribution (Border-3) is written as Eq.(5) and the Porosity.4.3.2.1 Measured Simulated (Tsutsumi et al, 26) -.1.2.4.6.8 1. 1.2 1.4 1.6 Standard deviation L Fig. 3 Comparison between the measured porosity and the simulated one for lognormal distribution Porosity.4.3.2.1. measured : dmax/dmin=1129 measured : dmax/dmin=21 measured : dmax/dmin=53 simulated : dmax/dmin=1 (Sulaiman et.al., 27) simulated: dmax/dmin=1 (Sulaiman, et.al., 27) 2 4 6 8 1 12 n T Fig.4 Comparison between the measured porosity and the simulated one for Talbot distribution border line between anti-talbot and lognormal distribution (Border-4) is expressed as Eq.(6). Fig.2 shows the domain for lognormal, Talbot and anti-talbot distributions. Border-3: (.5 ) 2. 25 (5) Border-4: (.5 ) 2. 75 (6) The porosity of various kind of grain size distribution can be obtained by means of a packing simulation model and an experimental method. As a result, the relation between the geometric parameter and the porosity is obtained as shown in Fig.3 and Fig.4 for lognormal distribution and Talbot distribution, respectively. The presented bed-porosity variation model was applied to the bed variation on a channel with a length of 15m and a width of.5m. The initial channel slope is.1. The end of the channel is fixed. The initial bed material has a lognormal type of grain size distribution ranging from.1mm to 1mm. The water is supplied at a rate of.2m 3 /s and no sediment is supplied. Under this condition, the maximum grain
could not be transported. Fig.5 (a), (b), (c) and (d) show the bed variation, the time and longitudinal variations of the mean grain size of surface layer and the porosity and the change in grain size distribution type. No sediment supply causes the bed degradation and the increase in porosity and mean grain size of the surface layer. Finally, the bed material had a Talbot type of grain size distribution. The validity of this model has not been verified yet, but it is believed that this model has a good performance for the analysis of bed and porosity variation. It could be applied for the problems on bed variation and ecosystem in the downstream of dam. Bed level (m) 1 ND1NS 9.9 min 3 min 6 min 24 min 6 min 9.8 5 1 15 Distance (m) (a) Bed variation Mean diameter of surface layer (m).1.8.6 ND1NS min.4 3 min 6 min 24 min 6 min.2 5 1 15 Distance (m) (b) Mean diameter of surface layer.4 ND1NS Porosity.3 24 min 3 min 6 6 min 24 min 3 6 min.2 5 1 15 Disatance (m) 5 Distance (m) 1 15 (c) Porosity of surface layer Time (min) 6 Lognormal Talbot (d) Type of grain size distribution Fig.5 Simulation result on bed and porosity variation References [1] Sulaiman, M., Tsutsumi, D., and Fujita, M. (27a): Porosity of Sediment Mixtures with Different Type of Grain Size Distribution, Annual Journal of Hydraulic Engineering, JSCE, Vol.51, pp. 133-138. [2] Tsutsumi, D., Fujita, M., and Sulaiman, M. (26): Changes in the void ratio and void structure of riverbed material with particle size distribution. River, Coastal and Estuarine Morphodynamics, Vol. 2, Parker, G., Garcia, M.H., eds., Taylor & Francis, pp. 159-165.
Background A Bed-Porosity Variation Model - as a tool for integrated sediment management- Dr. Masaharu Fujita Mr. Muhammad Sulaiman Dr. Daizo Tsutsumi DPRI, Kyoto University Targets of sediment management Disaster prevention Reduction of bad influence of sediment on rivers Effective utilization of sediment resources Environment conservation Tools Software bed variation models Hardware.. sabo dams, sediment flush gates, sediment bypass tunnel Ecological aspects Habitat conservation Disturbance to riverbeds Void of bed material Reservoir sedimentation management Situation of bed material Before flushing Just after flushing Impact of sediment flushing from Dashidaira dam and Unazuki dam 1 year after flushing Shizumi ishi situation Fine sand densely packed Lognormal type distribution Low porosity Lognormal type Uki ishi situation No fine sand packed Talbot type distribution High porosity Talbot type f f d d Grain size distribution type Void of bed material Bimodal distribution f f log d log d Unimodal distribution f f log d log d Porosity Bed variation Infiltration system in riverbeds Spaces among particles Habitat p p p p log(d) log d Talbot type log d Lognormal type log d Anti Talbot type A bed variation model providing the information on the changes in porosity and grain size distribution type of bed material
Basic equations Bh Q Continuity equation of water t x Continuity equation of sediment Energy equation for flows Q 2 Q 1 2 gbh gbhi b i f t x Bh 2 z t z o 1 Q B x z t q x s S 1 dz 1 Continuity equation of sediment Continuity equation of sediment with grain size d j t z z o z t zo 1 Q B x s 1 dz 1 Q B x sj 1 p dz B = channel width, h = water depth, Q = water discharge, t = time, x = distance in stream wise direction, = porosity of bed material, z = bed level, z o = a reference level, Q s = sediment discharge, g = gravity acceleration, i b = bed slope, i f = friction slope, j = grain size grade, p j = mixing ratio of a grade j in bed material and Q sj = sediment discharge of a grain size grade j j Continuity equation of sediment with grain size d j t z zo sj 1 p dz j z t 1 Q B x z t f j 1 BsqSj f j z t 1 abs x a t f j t 1 BsqSj f j z s 1 ab x a t A proposed model Porosity estimation zb 1 QS 1 dz t B x z t zo Sediment discharge Q S t,x,z sj 1 p dz j Bed surface z =z b Bottom z= 1 Q B x Compaction degree Grain size distribution f n 1, 2, 3,... 1, 2, 3.= characteristic parameters of grain size distribution Lognormal distribution: Talbot distribution: 1 1 d max / d min 2 nt Particle packing simulation and measurement method A bed variation model A bed-porosity variation model Water discharge Water discharge Flow analysis Sediment transport Grain size distribution of bed material Flow analysis Sediment transport Grain size distribution of bed material Geometric parameters Constant porosity Bed elevation Geometric parameters Porosity Bed elevation Implicit equations
Main routine and subroutine Temporally calculation of p j t+t Input data Flow analysis Temporal analysis of change of grain size distribution and porosity Bed variation analysis Analysis of change of grain size distribution and porosity Subroutine Identification of grain size distribution type Characteristic parameters of grain size distribution Estimation of the porosity t Bq t t s, j p j 1 1 abx xt tt p x j t t Bqs 1 abx xt 1 x Sediment balance within the surface layer at time t MacCormack scheme U C t x Q 2 Bh 1 2 Q E gbh U Q Q Bh C gbhi 2 b i z f s 1 dz zo B Water depth, water discharge and bed level Q U 2 h U1 / B z U 3 z o 1 dz z z dz z Rz where z U 3 R where R o z R R z z o z z o dz zo tt t zz z R( z ) dz zo z dz zo z t z t a R R Bed degradation t t t tt t t a z 1 1 2 tt t t a z 1 1 1 z t+t t+t t+t Bed aggradation t t t t+t t+t t+t z t z t Change in bed elevation z from t to t+t tt t 1 1 a U 3 z t 1 2 tt t 1 1 a U3 z t 1 1 1 t+t A layer bed model Grain size distribution at t+t
Change in grain size distribution t z p j zo t 1 Qsj, x, zdz B 1 x A layer bed model p1 j p1 j Bq 1 1 sj 2 z t t 1 1 t 1 1 ab x 1 z t 1 p 2 j z 1 a t p1 j p1 j Bq p 1 1 sj 1 j z t 1 1 t 1 1 ab x a t Lognormal type Classification of grain size distribution type f f d d p ln d Talbot and anti Talbot types n d d max n logd logd T min d d log max log min 2 1 ln d ln d mg exp 2 2 L 2 L Modified Talbot and anti Talbot types L 1 1 d max / dmin 2 n T Identification Geometric parameter of grain size distribution f Indices for lognormal distribution log d log d logd logd max max max max log d log d logd logd 5 min peak min 5% P d min d 5 d max d 1..5 Line-2 AT1 AT2 AT3 AT4 Anti-Talbot Area N3 B2 N2 D3 Border-2 Border-4 N1 D2 D1 Lognormal Area P2 P1 LN Q1 Q2 M3 Border-3 Border-1 C1 M2 C2 B3 M1 Talbot Area C3 B1 Percent finer (%) 1 8 6 4 Lognormal type LN 1 d min d peak d max d T4 T3 T2 T1. Line-1..5 1. 2 LN 3 LN 2.1.1 1 1 1 1 d (mm) Indices for Talbot distribution Indices for anti-talbot distribution 1. Line-2 AT1 AT2 AT3 AT4 1. Line-2 AT1 AT2 AT3 AT4 Anti-Talbot Area N3 Anti-Talbot Area N3 Border-2 D3 D2 B2 N1 N2 Border-4 Talbot type Border-2 D3 D2 B2 N1 N2 Border-4 Anti-Talbot type D1 D1.5 Lognormal Area P2 P1 LN Q1 Q2 1 T1 (nt=1.1).5 Lognormal Area P2 P1 LN Q1 Q2 1 AT 3 M3 Border-3 Border-1 C1 M2 C2 B3 M1 Talbot Area C3 B1 T4 T3 T2 T1. Line-1..5 1. Percent finer (%) 8 6 4 2 T2 (nt=2) T3 (nt=4) T4 (nt=16) T 1 T 2 T3 T 4.1.1 1 1 1 1 d (mm) M3 Border-3 Border-1 C1 M2 C2 B3 M1 Talbot Area C3 B1 T4 T3 T2 T1. Line-1..5 1. Percent finer (%) 8 6 4 2 AT 4 nt=.2 AT nt=.4 AT2 1 nt=.6 nt=.9.1.1 1 1 1 1 d (mm)
Domain of each type Identification 1. Line-2 AT1 AT2 AT3 AT4 1. Line-2 AT1 AT2 AT3 AT4 Anti-Talbot Area N3 Anti-Talbot Area N3 D3 B2 N2 D3 B2 N2 Border-2 D2 N1 Border-4 Border-2 D2 N1 Border-4 D1 D1.5 Lognormal Area P2 P1 LN Q1 Q2.5 Lognormal Area P2 P1 LN Q1 Q2 1 Border-3 M3 C1 Border-1 Border-3 M3 C1 Border-1 8 M2 C2 B3 M1 Talbot Area C3 B1 T4 T3 T2 T1. Line-1..5 1. M2 C2 B3 M1 Talbot Area C3 B1 T4 T3 T2 T1. Line-1..5 1. Percent finer (%) 6 4 2 M 1 M 2 M 3.1 1 1 1 1 d (mm) Identification Identification 1. Line-2 AT1 AT2 AT3 AT4 1. Line-2 AT1 AT2 AT3 AT4 Anti-Talbot Area N3 Anti-Talbot Area N3 D3 B2 N2 D3 B2 N2 Border-2 D2 N1 Border-4 Border-2 D2 N1 Border-4 D1 D1.5 Lognormal Area P2 P1 LN Q1 Q2 1 N 1.5 Lognormal Area P2 P1 LN Q1 Q2 1 M3 Border-3 Border-1 C1 M2 C2 B3 M1 Talbot Area C3 B1 T4 T3 T2 T1. Line-1..5 1. Percent finer (%) 8 6 4 2 N 2 N 3.1 1 1 1 1 d (mm) M3 Border-3 Border-1 C1 M2 C2 B3 M1 Talbot Area C3 B1 T4 T3 T2 T1. Line-1..5 1. Percent finer (%) 8 6 4 2 P 1 Q 2 Q 1 P 2.1.1 1 1 1 1 d (mm) Identification Percent finer (%) 1 8 6 4 2 O-1 O-2 O-3 F-1 F-2 F-3 Porosity and geometric parameter 1..9.8.7.6.5.4.3.2.1. A5 Anti-Talbot Area H2 H4 H1 Lognormal Area O3 O2 A3 Talbot A4 O1 H5 Lognormal H3 A2 Talbot--Log-normal Talbot Area Log-normal--Anti Talbot A1 Bimodal A6 H6 F3 F2 F1..1.2.3.4.5.6.7.8.9 1. Percent finer (%) Percent finer (%) 1 8 6 4 2 1.1.1.1 1 1 1 d (mm) 8 6 4 2 A-1 A-2 A-3 A-4 A-5 A-6.1 1 1 1 1 d (mm) H-1 H-2 H-3 H-4 H-5 H-6.1 1 1 1 1 d (mm) Porosity Two size particle mixture Ratio of finer particle
Porosity and geometric parameter Porosity and geometric parameter.4 Lognormal distribution.4 Talbot distribution.3 Porosity.3.2 Measured Simulated (Tsutsumi et al, 26).1 -.1.2.4.6.8 1. 1.2 1.4 1.6 Porosity.2.1. measured : dmax/dmin=1129 measured : dmax/dmin=21 measured : dmax/dmin=53 simulated : dmax/dmin=1 (Sulaiman et.al., 27) simulated: dmax/dmin=1 (Sulaiman, et.al., 27) 2 4 6 8 1 12 n T Standard deviation L Bed level (m) 1. 9.9 9.8 min 3 min 6 min 24 min 6 min Sediment supply Flow 5 1 15 Disatance (m) Case 1 Bed variation Case 2 Bed level (m) 1. Nosediment supply Flow 9.9 min 3 min 6 min 24 min 6 min 9.8 5 1 15 Disatance (m) Percent finer (%) 1 8 6 4 2 x=1m min 3 min 6 min 24 min 6 min Sediment supply.1.1 d (m) Case 1 Grain size distribution of surface layer Talbot to lognormal Time (min) 24 6 1 5 Lognormal Talbot Flow Disatance (m) Case 1 Grain size distribution type Case 2 Percent finer (%) 1 8 6 4 x=1m min 3 min 6 min 24 min 6 min Case 2 Time (min) 6 24 6 3 Lognormal Talbot Flow Lognormal to Talbot 2 No sediment supply.1.1 d (m) 5 1 15 Disatance (m)
Porosity.4.3.2 Flow Sediment supply min 3 min 6 min 24 min 6 min 5 1 15 Disatance (m) Case 1 Percent finer (%) 1 8 6 4 2 Porosity of surface layer x=1m min 3 min 6 min 24 min 6 min No sediment supply.1.1 d (m) Percent finer (%) 1 8 6 4 x=1m min 3 min 6 min 24 min 6 min.4 No sediment supply d 1 =2cm, d 2 =.5cm 2.1.1 d (m) Sediment supply Case 2 Porosity.3 min 3 min Flow 6 min 24 min 6 min.2 5 1 15 Disatance (m) Case 3 Bed material d 1 (9%), d 2 (1%) Supplied sediment d 2 very little Case 4 Bed material d 1 (7%), d 2 (3%) No sediment supply Deposition depth (m).6.5.4.3.2.1 -.1 Sediment supply min 3 min 12 min 24 min 36 min Flow Case 3 5 1 15 Disatance (m) Case 4 Deposition depth (m).6.5.4.3.2.1 No sediment supply min 5 min 1 min Flow Deposition depth 3 min 6 min 12 min Deposition depth (m).6.4.2 Constant porosity (Sediment supply) Not constant porosity (Sediment supply) Not constant porosity (No sediment supply) Constant porosity (No sediment supply) -.2 5 1 15 Distance (m) Deposition depth -.1 5 1 15 Disatance (m) Ratio of finer sediment 1.8.6.4 Sediment supply min 1 min 3 min 6 min 12 min 24 min Flow Case 3 Ratio of finer particle Porosity.5.4.3.2 Sediment Supply min 1 min 3 min 6 min 12 min 24 min Case 3 Porosity of surface layer.2 5 1 15 Disatance (m).1 Flow 5 1 15 Disatance (m) Case 4 Ratio of finer sediment 1.8.6.4.2 No sediment supply min 5 min 1 min Flow 3 min 6 min 12 min Case 4 Porosity.5.4.3.2.1 No sediment supply Flow min 5 min 1 min 3 min 6 min 12 min 5 1 15 Disatance (m) 5 1 15 Disatance (m)
Layer No. 2 4 6 8 Sediment supply x=14.5m x= 5.m T=36min 1.2.4.6.8 1 Ratio of finer sediment Layer No. 2 4 6 8 Sediment supply x=14.5m x= 5.m T=36min 1.1.2.3.4.5 Porosity Case 3 No sediment supply x=14.5m x= 5.m Vertical distribution of ratio of finer particle and porosity No sediment supply x= 14.5m x= 5.m Conclusions Identification method for grain size distribution type The relation between the geometric parameter of grain size distribution and the porosity Development of a bed-void variation model 2 2 Case 4 Layer No. 4 6 8 T=12min Layer No. 4 6 8 T=12min 1.2.4.6.8 1 Ratio of finer sediment 1.1.2.3.4.5 Porosity
Reservoir Sediment Management Measures in Japan and those appropriate selection strategy Dr. Tetsuya Sumi Kyoto University
Reservoir Sediment Management Measures in Japan and those appropriate selection strategy TETSUYA SUMI 1 1 Associate Professor, Department of Civil and Earth Resources Engineering, Graduate School of Engineering, Kyoto University The Japanese rivers are characterized by high sediment yield due to the topographical, geological and hydrological conditions. This has consequently caused sedimentation problems to many reservoirs constructed for water resource development or flood control purposes. The necessity for the reservoir sediment management in Japan can be summarized in the following three points: 1) to prevent the siltation of intake facilities and aggradations of upstream river bed in order to secure the safety of dam and river channel, 2) to maintain the storage function of reservoirs, and realize sustainable water resources management for the next generation, and 3) to release sediment from dams with an aim to conduct comprehensive sediment management in a sediment routing system. Sediment management approaches are largely classified into the following techniques: 1) to reduce sediment transported into reservoirs, 2) to bypass inflowing sediment and 3) to remove sediment accumulated in reservoirs. In Japan, in addition to conventional techniques such as excavation or dredging, sediment flushing and sediment bypass techniques are adopted at some dams: e.g. at Unazuki and Dashidaira dams in the Kurobe river, and at Miwa dam in the Tenryu river and Asahi dam in the Shingu river as shown in Figure 1, respectively. These dams practically using such techniques are focused on as advanced cases aiming for long life of dams. In addition to these dams, larger scale sediment bypass systems are now under studying at Sakuma and Akiba dams in the Tenryu river, and Yahagi dam. The problems to promote such reservoir sediment management in future are 1)Priority evaluation of reservoirs where sediment management should be introduced, 2)Appropriate selection of reservoir sediment management strategies and 3)Development of efficient and environmental compatible sediment management technique. In order to decide priority and appropriate sediment management measures, Capacity-inflow ratio and Reservoir life indices are useful for guidance as shown in Figure 2. When the sediment management measures are selected, it is also necessary to consider those environmental influences in the downstream river and coastal areas both from positive and negative point of views. In this paper, state of the art of reservoir sediment management measures in Japan and future challenges are discussed. Keywords: Reservoir sediment management, sediment routing system, sediment bypassing, sediment flushing, environmental impact assessment, Tenryu river, Yahagi river
Classification Place Details of sediment control measures Examples in Japan Sediment management Reducing sediment flowing into reservoirs Sediment routing Upstream reservoirs End of reservoirs End of reservoirs Inside reservoirs Reduction of sediment production by hillside and valley works Regulation of reservoirs and sediment by erosion control dams and slit dams Reduction of discharged sediment and river course stabilization by channel works Sediment check dam Sediment bypass Sediment sluicing Density current venting Regurally excavating and recycling for aggregate or sediment supply to downstream river Non-gate botom outlets natural flushing Botom outlets for flood control Sabo area, Changing from sediment check dams to sediment control dams (slit dams) Miwa Dam, Koshibu Dam, Nagashima Dam, Matsukawa Dam, Yokoyama Dam Asahi Dam, Miwa Dam, Koshibu Dam, Matsukawa Dam, Yokoyama Dam Sabaishigawa Dam Dashidaira Dam-Unazuki DamCoordinated sluicing Masudagawa Dam Koshibu Dam, Futase Dam, Kigawa Dam Non-gate conduits with curtain wall Katagiri Dam Selective withdrawal works Yahagi Dam Drawdown flushing Sediment flushing outlet Dashidaira Dam-Unazuki DamCoordinated flushing Sediment flushing Inside reservoirs Partial flushing without drawdown Sediment scoring gate Senzu Dam, Yasuoka Dam Sediment scoring pipe Ikawa Dam Excavating & Dreging Recycling for concrete aggregate Soil improving material, Farm Land filling, Banking material Miwa Dam, Koshibu Dam, Sakuma Dam, Hiraoka Dam, Yasuoka Dam Miwa Dam, Yanase Dam Sediment replacing inside reservoir Sakuma Dam Sediment supplying to downstream rive Akiba Dam, Futase Dam, Miharu Dam, Nagayasuguchi Dam, Nagashima Dam Figure 1. Classification of Reservoir Sedimentation management in Japan No measures (from inner factors) Sediment check dam, Sediment replenishment Sediment bypass, Sluicing Sediment flushing, Sediment scoring gate Figure 2. Appropriate selection of reservoir sediment management strategy References [1] T. Sumi, Baiyinbaoligao and S. Morita, 1th International Symposium on River Sedimentation, Moscow, CD-ROM, (27). [2] T. Sumi and H. Kanazawa, 22nd International Congress on Large Dams, Barcelona, Q.85-R.16, (26).
Contents of presentation Reservoir Sediment Management Measures in Japan and those appropriate selection strategy Kyoto University Tetsuya SUMI Reservoir sedimentation in Japan Reservoir sediment management measures in Japan Sediment bypassing Sediment flushing and environmental issues Promotion strategy of reservoir sediment management Conclusions Reservoir National Inventory of reservoir sedimentation sedimentation 273 dams (>15m high) with 23 billion m 3 capacity. in Sedimentation Japan progress of all reservoirs over 1 million m 3 have been reported annually to the government from 198s. In 922 dams of 18 billion m 3 volume, total sedimentation 7.4% annual loss.24%/yr Sediment yield potential map of Japan Median Tectonic Line Itoigawa-Shizuoka Tectonic Line m 3 /km 2 /yr Total sedimentation losses Some hydroelectric dams constructed before World War II more than 5 years old 6 to 8 %,%, but problems are depend on the cases. Many cases from 195 and 196 through the high economic growth period more than 3 years old beyond 4 %. From 196s, large numbers of multi-purpose dams 1 to 3 % Maintaining effective storage capacity is critical for flood control and water supply. Total average sedimentation rate 7.4% (1.35 /18.3 billion m3) Need for reservoir sedimentation management 3 points Safety Management for Dams and Rivers To prevent the siltation of intake and other hydraulic facilities and aggradations of upstream rivers Sustainability of Water Storage Volume Comprehensive Management of Sediment Routing System in a River Basin and Connected Shoreline Scale To prevent riverbed degradation, river morphology change and coastal erosion caused by shortage of necessary sediment supply from upstream including dams Comprehensive Management of Sediment Routing System in a River Basin and Connected Shoreline Scale Balancing of sediment transport from the source of the river to the coast Lack of sediment supply Coastal erosion Sedimentation Riverbed degradation River environment change Check dam Storage reservoir Sediment flow monitoring Bed load Suspended load Wash load 1
Yasuoka dam(1936,11mcm) Miwa dam(1959,3mcm) Hiraoka dam(1951,43mcm) Koshibu dam(1969,58mcm) Tenryu River Mouth Sakuma dam(1956,327mcm) Sediment suppy Yasuoka dam (1936) Akiba dam(1958,35mcm) 1946 Hiraoka dam (1951) Sakuma dam (1956) Akiba dam (1958) 1961 Miwa dam (1959) Dicrease Koshibu dam (1969) Tenryu River, A=5,9km2 21 㪊㪉㪇 ᐔጟ䉻䊛 㪊㪇㪇 ᣂ 㔚ᚲ ญ 㪉㪏㪇 21yr 㪉㪍㪇 11yr 䉪䊧䉴䊃ᢝ㜞 㪜㪣㪉㪋㪍㪅㪌㫄 㪉㪋㪇 Ꮉ ข ญ 㪉㪉㪇 㪉㪇㪇 ਭ㑆䉻䊛ᑪ ೨䈱ᴡᐥ㜞 ᤘ 㪌㪌ᐕᐲᦨ ᴡᐥ㜞 Tenryu River Dam Redevelopment Project HSRS: Hydro-suction Sediment Removal System 㪇 㪈㪇 㪈㪌 㪉㪇 㪉㪌 㪊㪇 㪈㪍㪇 㪈㪋㪇 㪈㪉㪇 㪈㪇㪇 㪊㪌 䉻䊛䈎䉌䈱 㔌㩿㫂㫄㪀 Reservoir sediment management measures in Japan Sakuma dam Excavating Sediment check dam Diversion weir Akiba dam Sediment Transport: Transport sediment in reservoir by dredging or other methods 㽵Sluicing 䊶 ԛ ࡈ Flushing 㪌 㪈㪏㪇 ᵹ Ᏹ ḩ ၸ 㪈㪇㪈ᐕᓟ ၸ 㪉㪇㪈ᐕᓟ ᑪ ೨ᴡᐥ൨㈩䈱㪈㪆㪉൨㈩䈪ၸ 䋨ᵏ㒂䉻䊛䈱ታ ୯䋩 ᑪ ೨ᴡᐥ൨㈩䈱㪈㪆㪊㪅㪉൨㈩䈪ၸ 䋨ᐔጟ䉻䊛䈱ታ ୯䋩 ᐔጟ ጯ㜞 ᄤ ਛቇ ᐔጟ㪧㪪 ਭ㑆 㔚ᚲ ข ญ J-Power (EPDC) 1956 Power generation Gravity concrete Height=155.5 m 㜞㩿㪜㪣㫄㪀 Future estimation of reservoir sedimentation in Sakuma dam Reservoir sedimentation in Sakuma dam Afforestation Sediment bypass tunnel ਭ㑆 ࡓ Sakuma dam Ԛ ኒᐲᵹឃ 㽴Density Current Venting Dredging Trucking ⑺ ࡓ Akiba dam Density current venting Ԝ ๆᒁᣇᑼ 㽶HSRS+Sediment 㧗ឃ ࡀ bypass+sediment 㧗ḓ ャㅍ Transport Ԟ ๆᒁᣇᑼ㧗ឃ ࡀ 㧗ḓ ャㅍ 㽸HSRS+Sediment bypass+sediment 㧔 ࡓㅪ 㧕 Transport (Two dams) Ԙ ឃ ࡃ ࡄ ࡀ 㽲Sediment Bypass Tunnel ኒᐲᵹឃ Sediment scoring gate Reducing Sediment Inflow Sediment Routing ԙ ๆᒁᣇᑼ㧗ឃ ࡀ 㧗ḓ ャㅍ 㽳HSRS+Sediment Bypass+Sediment Transport 㽷Sediment Bypass Tunnel ԝ ឃ ࡃ ࡄ ࡀ ࡓㅪ 㧕 (Two 㧔 dams) ᴡᎹ ㆶర Sediment supply Sediment Removal 䋭㩷㪈㪌㪋㩷䋭 2
Reservoir sediment management measures in Japan Excavating Sediment check dam Diversion weir Typical sediment management dams in Japan Afforestation Sediment bypass tunnel New project Unazuki dam Matsukawa dam Dredging Density current venting ኒᐲᵹឃ ᴡᎹ ㆶర Yahagi dam Trucking Miwa dam Reducing Sediment Inflow Sediment scoring gate Asahi dam No Name of Dam Country Tunnel Shape Tunnel Cross Section (B H(m)䋩 Tunnel Length (m) General Slope (%) Tenryu river Nagoya Design Design Discharge Velocity (m/s) (m3/s䋩 Operation Frequency 1 Nunobiki Japan 198 Hood 2.9 2.9 258 1.3 39-2 Asahi Japan 1998 Hood 3.8 3.8 2,35 2.9 14 11.4 13 times/yr 3 Miwa Japan Horseshoe 2r = 7.8 4,3 1 3 1.8-4 Matsukawa Japan Hood 5.2 5.2 1,417 4 2 15-5 Egshi Switzerland 1976 Circular r = 2.8 36 74 9 1days/yr 6 Palagnedra Switzerland 1974 Horseshoe 1,8 2 11 7 Pfaffensprung Switzerland 1922 Horseshoe 2r = 6.2 A= 21.m2 28 3 22 8 Rempen Switzerland 1983 Horseshoe 3.5 3.3 45 4 9 Runcahez Switzerland 1961 Horseshoe 3.8 4.5 572 1.4 24 Under construction Nunobiki dam Sediment Removal Sediment bypassing dams in the world Tunnel Completion 2.6 Sakuma and Akiba dams Bypassing Nagano Outline of Miwa dam Tokyo Dam Sediment trap weir (H=15.m) Diversion weir (H=2.5m) 1959, H=69m V=29.95 V=29.95 MCM A=311km A=311km2-2䌾5days/yr 䌾 1䌾15 2days/yr 9 8 䌾14 1䌾5days/yr 11 9 4days/yr Sediment bypass tunnel 25, A=5m2 L=43m Bed and suspended load 18, m3 Wash load 535,m3 Wash load (Five bypass tunnels in Switzerland by Visher et al., 1997) Sediment bypass (Miwa dam) Bypassing Koshibu dam Sediment Routing Sediment supply Flushing Dashidaira dam Purpose: Multipurpose Flood control Irrigation Water power Miwa dam Bypass operation in 26 Diversion weir Sediment check dam Bypass discharge Sediment check dam Diversion weir 7.5m L=4,3m Tunnel outlet 7.5m 䋭㩷㪈㪌㪌㩷䋭 3
Sediment flushing in the Kurobe River Kurobe river Catchment area = 682km 2 River length = 85km H=185m High mountains >3m Dashidaira dam (1985) H=76.7m, V=9 MCM Unazuki dam (21) H=97m, V= 24.7 MCM Sediment flushing dams in the World Application of Sediment Flushing from the view point of water use Flushing Coordinated sediment flushing in Kurobe river 29hr 53hr 44hr 68hr Sediment flushing rule by the river committee: During rainy season from June to July Timing of natural floods exceed discharges 3m 3 /s Sedimentation profiles Elevation (m) 23 24 AF 24 BF 1, 2, 3, 4, 5, Unazuki dam Original bed 21 4 Elevation (m) 38 36 34 32 3 24 24 BF AF Original bed 1985 28 5 1, 1,5 2, 2,5 3, Dashidaira dam BF: Before flushing AF: After flushing 1995 1994 Sedimentation Amount 1 3 m 3 Sedimentation volume change in Dashidaira dam 9 Gross storage: 91 6 m 3 1721 3 m 3 8 81 3 m 3 7 281 The biggest flood in 1995 3 m 3 71 3 m 3 6 3451 3 m 3 61 3 m 3 5 81 3 m 3 4 3 591 3 m 3 2 341 3 m 3 21 3 m 3 461 3 m 3 1 461 3 m 3 91 3 m 3 '85 '86 '87 '88 '89 '9 '91 '92 '93 '94 '95.6 '95.7 '95.11 '96 '97 '98 '99 ' '1 '2 '3 4 Cross section Side bank erosion Degradation 4
Subjects of sediment flushing Flushing efficiency =scoured sediment volume / water use Flushing effect = scoured sediment volume / total deposited sediment volume before flushing Environmental impacts the influences of SS rising and DO dropping - duration time etc. SS: Suspended solid concentration DO: Dissolved oxygen Study on sediment discharge process during flushing operations from quantity and quality point of view is very important. Total water use and flushed sediment volume in sediment flushing dams 4 99 1 97 2 F e : Flushing efficiency =Total flushed sediment volume/ Total water volume 95 3 98 96 Flushing efficiency of Sediment flushing dams F e : Flushing efficiency =Total flushed sediment volume/ Total water volume Environmental monitoring during sediment flushing Sea Water quality (DO, SS etc.) Mud quality Aquatic species Cross sections N Shimokurobe -25-15 -5 5 1 km Unazuki dam River Water quality (DO, SS etc.) Mud quality Aquatic species Cross sections Dashidaira dam Reservoir Water quality (DO, SS etc.) Mud quality Cross sections Discharge (m3/s) Discharge (m3/s) SS (mg/l) 24/7/16 7/17 7/18 7/19 7/2 Average hourly rainfall (mm) Water level (EL.m) Water level (EL.m) Sediment flushing in July 24 Measurement values of DO and SS during flushing Amount of DOmg/l SSmg/l Sediment flushing Dashidaira Minimum value) Maximum value sediment Shimokurobkurobe Shimo- Dashidaira Unazuki Dashidaira Unazuki Year Event flushing Jul-95 Flood 11.3 1.5 3,7 1,8 Oct-95 Flushing 1.72MCM 8.8 9.7 8.9 13,5 29,4 26, Jun-96 Flushing.8MCM 1.7 1.3 9.8 56,8 9,47 6,77 Jul-97 Flushing.46MCM 9.8 9.2 9.3 93,2 28,9 4,33 Jun-98 Flushing.34MCM 8.2 7. 7.3 44,7 9,4 6,75 Jul-98 Flood 1.5 9.5 6,9 5,26 Sep-99 Flushing.7MCM 6. 5.8 6.5 161, 52,1 25,7 Coordinated Jun-1.59MCM 7.2 11.4 1.2 9, 2,5 1,5 flushing Coordinated Jul-1 11.1 1.6 9.6 29, 3,7 2,2 sluicing Coordinated Jul-2.6MCM 9.5 1.5 9.5 22, 5,4 2,8 flushing Coordinated 11.8 11.3 9.6 69, 17, 1, Jun-3 flushing.9mcm Coordinated Jul-4.28MCM flushing 9.3 1.2 9.8 42, 6,8 11, Jul-4 Flood 1.8 11.2 1.3 3, 12, 14, Coordinated Jul-4 sluicing 1.6 11.2 9.6 16, 17, 21, Manual sampling in every one hour Continuous monitoring method for DO and SS is necessary Development of new techniques for high SS monitoring 5
Balancing of Flushing efficiency and environmental impacts Promotion strategy of reservoir sediment management Flushing efficiently = Little water High sediment concentration Water use Flushing naturally = Much water Low sediment concentration Reservoir draw down Enough flushing discharge water Rinsing discharge after flushing, etc. A) Priority evaluation of reservoirs where sediment management should be introduced B) Appropriate selection of reservoir sediment management strategy C) Development of efficient and environmentally compatible sediment management techniques A) Priority evaluation of reservoirs where sediment management should be introduced B) Appropriate selection of reservoir sediment management strategy Reservoir sustainability factor - Reservoir life = CAP/MAS Comprehensive sediment management factor - impacts to the downstream river and an actual environmental deterioration degree Technical difficulty factor CAP/MAS <1yrs, 34% CAP/MAS= 5-1yrs, 25% CAP/MAS<1yrs, 7% CAP/MAS=1-5yrs, 34% Reservoir lives (CAP/MAS) of multipurpose dams in Japan No measures (from inner factors) Sediment check dam, Sediment replenishment Sediment bypass, Sluicing Sediment flushing, Sediment scoring gate C) Development of efficient and environmentally compatible sediment management techniques "Take", "Transport" and "Discharge" - Sediment flushing/sluicing and sediment bypassing should be introduced more. - The sediment trucking and supply, and the Hydro-suction Sediment Removal System (HSRS) are needs to be improved furthermore and introduced as supplementary measures. Sediment property and recycling Washload+Suspended load Bed load+suspended load Bed load Sediment replenishment Suspended load Fore set bed Wash load Bottom set bed Top set bed Sediment recycling for Flood discharge Delta construction materials and so on Washload Sediment property Recycling infeasible Downstream area Delta Middle area Upstream area Size Clay, silt Mainly sand Sand and gravel Grain size Gravel=, Gravel=1, Gravel=3, Sand=1, Sand=45, Sand=4, content(%) Clay=5, Silt=4 Clay=3, Silt=15 Clay=2, Silt=1 Fine sediment Fc=over9% Fc=45-5% Fc=lower3% Water content w=over1% w=5-6% w=lower4% Density, Porosity Small Large Ignition loss Ig=over1% Ig=ca.8% Ig=ca.4% Nutrients Recycling feasible Large Small 6
HSRS (Hydro-suction Sediment Removal System) Fixed type - Vortex tube - Hydro pipe - Multi-hole suction sediment removable system Movable type - Hydro J - SY system SY SYSTEM HYDRO PIPE MULTI HOLE SUCTION SEDIMENT REMOVABLE SYSTEM HYDRO J Conclusion Current status of reservoir sedimentation in Japan are ; total sedimentation loss is 7.4%; annual loss is.24%/yr. Reservoir sediment management is important from the view points of reservoir safety, sustainability and the comprehensive management of sediment routing system. Bypassing is suitable for sediment management of existing dams. Flushing is effective and Flushing efficiency, Flushing effect and Environmental impacts of sediment flushing are to be studied more and it is important to cause them a balance. Promotion strategy of reservoir sediment management should be established by the following points; - Priority evaluation of reservoirs where sediment management should be introduced - Appropriate selection of reservoir sediment management strategy - Development of efficient and environmentally compatible sediment management techniques. Kurobe alluvial fan Sediment discharge from Unazuki dam Thank you for your attention! 7