1 INVESTIGATION OF TOTAL SUSPENDED MATTER IN PORONG REGION USING AQUA-MODIS SATELLITE DATA AND NUMERICAL MODEL Bambang Sukresno* 1, Bayu Priyono 2, Dedy Aan Zahrudin 3, Berny A Subki 4 1 Institute for Marine Research and Observation 2 Institute for Marine Research and Observation 3 Institute for Marine Research and Observation 4 Institute for Marine Research and Observation ABSTRACT Total suspended mater (TSM) in Porong region has been investigated. TSM of Porong region was one of important parameter to be observed according to mud volcano that occurred in 28 May Location of this research was Porong region between Longitude E E and latitude S S. The research was carried out using MODIS-Aqua satellite 250 m resolution dataset received in 2006, 2007 and band 1 reflectance images were geo-corrected, land and cloud areas were masked out. TSM concentration derived from MODIS-Aqua satellite by applying algorithm suggested by Kutser (2007). Surface water samples were obtained from 16 location of Porong region in June 15, and filtered for the determination of Total Suspended Matter (TSM). TSM concentration (mg/l) was determined gravimetrically in Laboratory.Sediment transport in coastal water calculated based on current pattern derived from hydrodynamic model. The equation used in this calculation was horizontal 2 dimension diffusion advection. Result of this research show that TSM of Porong region is vary in the range of mg/l, and affected by rainfall according to monsoon. During northwest monsoon TSM was higher than it in southeast monsoon. Generally TSM in Porong region had not yet significantly increase caused by mud volcano as found in processed satellite data in 2006 before mud volcano occurs, 2007 and 2008 after that event. Current pattern of Porong region is continuously change the direction according to tide in this area. During ebb condition, current flow downstream, while during flood condition is upstream. Generally component current pattern of Porong region flow southward with velocity up to 1.0 m/s, while velocity of current in coastal region is less than that or about 0.4 m/s. Distribution of sediment affected by tidal current. During flood condition sediment transport is blocked in mouth of Porong river. During ebb condition sediment transport get maximum velocity and distribution. Key Word : Total Suspended Mater, Aqua-Modis Satellite data, Numerical model
3 Introduction The mudflow in Sidoarjo, East Java is an eruption of a mud volcano at a depth of between 1-2 km s below the surface of the earth. On 28 May 2006, PT Lapindo Brantas targeted gas in the Kujung Formation carbonates in the Brantas PSC area by drilling a borehole named the 'Banjar-Panji 1 exploration well', at this stage the borehole was surrounded by a steel casing to help stabilise it. At 5:00 a.m. local time (UTC+8) a second stage of drilling began and the drill string went deeper, to about 2,834 m (9,298 ft), this time without a protective casing, after which water, steam and a small amount of gas erupted at a location about 200 m southwest of the well. Two further eruptions occurred on the second and the third of June about m northwest of the well, but these stopped on 5 June During these eruptions, hydrogen sulphide gas was released and local villagers observed hot mud, thought to be at a temperature of around 60 C. (Wikipedia, 2008) There are many alternative suggested after effort to stop eruptions was fail. one of the most feasible alternative to solve the problem is channeled mud into the sea through Porong river without any special process. channeling mud through Porong river supported by utilize of three pump with capacity about m 3 /hours, it s mean that m 3 hot mud will flow into the sea per day. By assuming that half of it s volume will remain in the river as sediment, there are about m 3 /day mud will flow into the sea. this condition exactly will affected coastal area. (Priyono, et al, 2007). To mitigate the disaster according to process of mud channeling to the sea, there is needed to perform continuous monitoring and observation of river and coastal conditions. One of important river and coastal condition to be observed was suspended mud or total suspended mater (TSM). This parameter can be observed directly by performing in situ measurement. On the other side by using remote sensing technology, TSM can be daily observed in both value and distribution pattern.
4 The utilizing of MODIS data for analyze complex coastal waters was examined in the Northern Gulf of Mexico. Using simple processing procedures, MODIS images were used to map the concentration of Total Suspended Matter (TSM). High concentrations of suspended particulate matter in coastal waters directly affect or govern numerous water column and benthic processes. The concentration of suspended sediments derived from bottom sediment resuspension or discharge of sediment-laden rivers is highly variable over a wide range of time and space scales. (Miller, 2004). MODIS band 1 imagery is the only satellite data with acceptable spatial resolution (250 m) and sufficient revisit times (up to 4 times a day) potentially available for monitoring dredging plumes. These advantage to determine the potential use of MODIS band 1 imagery in an optically sophisticated environment coastal waters for monitoring of total suspended matter in natural conditions and near dredging activities. It was found that there is linear correlation between MODIS band 1 ( nm) reflectance and the total suspended matter concentration measured from water samples. The regression algorithm was used to produce suspended matter concentration maps and monitor dredging activities. ( Kutser, T., et al. 2007) These research completed by numerical model calculation to get distribution pattern of TSM based on current pattern simulation, in order to investigate susceptance level of coastal area caused by these eruption. During process of numerical model, there is requirement of database of spatial and temporal condition, especially physical condition, chemistry, and biology. Database needed in these research provided by primary and secondary dataset. Secondary dataset obtained from other institution which is performed previous study in this area. Dynamical condition of research area and lack of secondary dataset resulting the importance of in situ measurement. Primary dataset obtained from in situ measurement give the image of recent situation, that can be used as complement dataset to fill lack of secondary dataset. Combination
5 of remote sensing method with numerical model will give more optimum result, then verified using in situ measurement. Based on previous research and motivated by high need of observation database, this research aimed to get further knowledge of the total suspended mater (TSM) as derived from satellite dataset, current pattern and sediment transport derived from numerical model in Porong region. Total Suspended mater Waters are often characterized by high concentrations of suspended organic and inorganic materials. Suspended materials serve as a carrier and storage agent of pesticides, absorbed phosphorus, nitrogen and organic compounds and can be an indicator of pollution. Therefore, it is very important to monitor and assess the concentrations of suspended materials in lake waters, as well as their spatial and temporal distribution and change. (Jensen, 2000, in Zhou 2005). The amount of particles that suspend in a sample of water is called total suspended Mater (TSM). To remain permanently suspended in water (or suspended for a long period of time), particles have to be light in weight (they must have a relatively low density or specific gravity), be relatively small in size, and/or have a surface area that is large in relation to their weight (have a shape like a sheet of paper). The greater the TSM in the water, the higher its turbidity and the lower its transparency (clarity). Aqua-Modis Satellite MODIS (Moderate Resolution Imaging Spectroradiometer) is a key instrument aboard the Terra (EOS AM) and Aqua (EOS PM) satellites. Terra's orbit around the Earth is timed so that it passes from north to south across the equator in the morning, while Aqua passes south to north over the equator in the afternoon. Terra MODIS and Aqua MODIS are viewing the entire Earth's surface every 1 to 2 days, acquiring data in 36 spectral bands, or groups of wavelengths. These data will improve our understanding of global dynamics and processes occurring on the
6 land, in the oceans, and in the lower atmosphere. MODIS is playing a vital role in the development of validated, global, interactive Earth system models able to predict global change accurately enough to assist policy makers in making sound decisions concerning the protection of our environment. (NASA, 2008) Specifications of MODIS satellite can be seen in Table 1. Table 1. Specifications of MODIS Aqua / Terra Satellite Primary Use Band Bandwidth 1 Spectral Radiance 2 Land/Cloud/Aerosols Boundaries Required SNR 3 Land/Cloud/Aerosols Properties Ocean Color/ Phytoplankton/ Biogeochemistry Atmospheric Water Vapor Surface/Cloud Temperature (300K) (335K) (300K) (300K) 0.07
7 Atmospheric Temperature Cirrus Clouds Water Vapor (250K) (275K) (SNR) (240K) (250K) 0.25 Cloud Properties (300K) 0.05 Ozone (250K) 0.25 Surface/Cloud (300K) 0.05 Temperature (300K) 0.05 Cloud Top (260K) 0.25 Altitude Bands 1 to 19 are in nm; Bands 20 to 36 are in µm 2 Spectral Radiance values are (W/m 2 -µm-sr) 3 SNR = Signal-to-noise ratio 4 NE(delta)T = Noise-equivalent temperature difference It was found that there is linear correlation between MODIS reflectance and the total suspended matter concentration measured from water samples. The regression algorithm was used to produce suspended matter concentration maps and monitor dredging activities. Hydrodynamic Model Coastal water mass motion developed by tidal and wind force generally explained with momentum conservation equation and mass conservation equation. In two dimension Cartesian coordinate system, coastal hydrodynamic condition can be displayed as :
8 Equation of Continuity : Equation of motion in x axis and y axis : where u = Current velocity in x axis, normalized to sea depth (m/s); v = Current velocity in y axis, normalized to sea depth (m/s); h = sea surface elevation (m) h = Total depth of the sea (m); h = h0 + h f = coriolis force ( sec -1 ); f = 2Wsin ( F ), which W : radian of earth rotasion (~7.292 x 10-5 rad/sec) and F = latitude. A h = horizontal Eddy viscosity coefficient ( m 2 /s ) g = earth gravity ( m/sec 2 )
9 ρ 0 = water density ( kg/m 3 ) τ sx and τ sy = surface stress (N/m 2 ) τ bx and τ by = bottom stress (N/m 2 ) In shallow water and calm wind speed, bottom stress become dominant than surface stress. The equation become : where r = 3 x Method Location of this research was Porong region between Longitude E E and latitude S S as shown in figure.1 Figure. 1 Research location
10 The research was carried out using MODIS-Aqua satellite dataset received in 2006, 2007 and MODIS 250 m resolution data was downloaded from NASA web page MODIS band 1 reflectance images were geo-corrected, land and cloud areas were masked out. TSM concentration derived from MODIS-Aqua satellite by applying algorithm suggested by Kutser (2007): TSM = *B1 Where TSM : Total Suspended Mater (mg/l) B1 : MODIS band 1 reflectance (Rrs) Remote sensing reflectance (Rrs) is the standard input to many of the derived product algorithms. It is computed as Rrs = nlw / F0 where F0 is mean solar irradiance of a wavelength. The "best" value of F0 depends on whether nlw is computed as a full bandpass value, or nominal band center value (outband_opt=2), meaning that it is corrected to a 10-nm square bandpass, centered at the sensor nominal wavelength. For standard processing, the nlw is reported as a nominal band value. MODIS (Aqua or Terra) Nominal Band Solar Irradiances can be found in table.2 Table.2 Nominal Band Solar Irradiances of MODIS Wavelength (nm) mw/cm^2/um
11 Surface water samples were obtained from 16 location of Porong region in June 15, and filtered for the determination of Total Suspended Matter (TSM). TSM concentration (mg/l) was determined gravimetrically in Laboratory Sediment transport in coastal water calculated based on current pattern derived from hydrodynamic model. The equation used in this calculation was horizontal 2 dimension diffusion advection : where : C u and v K x and K y = Local sediment consentration (mg/l) = fluid velocity in x axis and y axis (m/s) = dispersion coefficient in x axis and y axis (m 2 /s) ϕ r = resuspension flux as erosion therm (kg m -2 s -1 ) ϕ s = sedimentasion flux as deposition therm (kg m -2 s -1 ) h = total dept of water (h = h o + η ) (m)
12 Result and Discussion Since mud volcano is occurred in may, 28 th 2006 and partly channeled into the sea through Porong river without any special process in 2007 until this time, MODIS Aqua that acquired and processed was dataset of 10 February 2006, 29 September 2006, 20 February 2007, 15 June 2007,27 September 2007, 22 january 2008, and 30 june 2008, consist of northwest monsoon and southeast monsoon. MODIS-Aqua in 10 February 2006 show distribution of TSM in Porong region before mud channeling into the sea trough Porong river as displayed in figure mg/l 0.1 Figure.2 TSM of Porong region in 10 February 2006 As shown in figure.2 TSM in 10 February 2006 not distributed in wide area. High concentration of TSM accumulated around mouth of Porong river represented by red color. February represent northwest monsoon which is wet season in Indonesia. Wet season characterized by high rainfall, in which will increase debit of Porong river.
13 TSM of Porong region is vary in range of mg/l until max mg/l. TSM of coastal area in northward of Porong river is about mg/l. while southward of it is about mg/l. TSM in the Madura strait is around mg/l mg/l. TSM of Porong region during southeast monsoon is represent by processed image of MODIS-Aqua in 29 September 2006 as displayed in figure. 3. Debit of Porong river during this dry season is lower than it in wet season caused by low of rainfall. 200 mg/l 0.1 Figure.3 TSM of Porong region in 29 September 2006 Pattern of TSM distribution in 29 September 2006 is widely spread compare with pattern of TSM in February, but concentration of TSM in this period is lower than it in February. TSM in mouth of Porong river is about mg/l. northward of mouth of Porong river is higher, about mg/l. while southward of it is about 49.4 mg/l. TSM around Madura strait is about mg/l. In 20 February 2007 image of processed MODIS-Aqua data show pattern of TSM in Porong region as displayed in figure. 4
14 200 mg/l 0.1 Figure.4 TSM of Porong region in 20 February 2007 Low concentration of TSM occurs in this region. southward of Porong river and Madura strait is characterized by TSM about 37.4 mg/l. TSM of northward of Porong river is generally mg/l. maximum of TSM occurs in mouth of Porong river with concentration up to mg/l but not widely distributed. Note that black color is cloud cover that masked out before MODIS-Aqua dataset processed. During southeast monsoon or dry season of 2007, TSM of Porong region displayed in figure mg/l 0.1 Figure.5 TSM of Porong region in 27 September 2007
15 Figure.5 is TSM of Porong region in 27 September During this period concentration of TSM is much higher then it in wet season of widely spread of TSM is observed in Porong region as represent by red and yellow color in above figure. Maximum concentration of TSM accumulated in northward of Porong river about mg/l. mouth of Porong river marked by yellow to red color indicate TSM about mg/l. while southward and Madura strait represented by green color indicate TSM mg/l. TSM of Porong region in 22 January 2008 can be seen in figure mg/l 0.1 Figure.6 TSM of Porong region in 22 January 2008 Generally TSM during wet season of 2006 is widely distributed to Madura strait, indicated by concentration about mg/l. maximum concentration observed in northward of Porong river up to mg/l. mouth of Porong river is characterized by mg/l concentration, while TSM of southward of Porong river is about mg/l.
16 In 30 June 2008, TSM of Porong region also observed as shown in figure mg/l Figure.7 TSM of Porong region in 30 June Concentration of TSM in mouth of Porong river, southward and northward of Porong river is almost similar in range of mg/l mg/l, meanwhile Madura strait characterized by low concentration of TSM about 22.2 mg/l. From processed MODIS-Aqua dataset in 15 June 2007, then compared with in situ measurement, we found that TSM algorithm by Kutser (2007) resulting over estimated value of TSM derived from MODIS as shown in Table.3
17 Table.3 Comparison of in situ TSM and MODIS derived TSM NO Longitude Latitude insitu TSM (mg/l) MODIS TSM (mg/l) TSM '47.8" 07 31'51.3" '30.0" 07 32'29.7" '47.2" 07 33'10.6" '35.7" 07 33'39.0" '24.6" 07 34'53.5" '20.8" 07 35'45.9" '21.0" 07 34'54.3" '21.0" 07 34'04.0" '21.0" 07 33'06.1" '24.5" 07 30'58.2" '24.5" 07 32'05.0" '24.5" 07 33'06.3" '17.7" 07 35'45.7" '17.7" 07 34'54.1" '17.7" 07 34'03.8" '17.7" 07 33'05.9" Average of TSM As shown above, TSM from in situ measurement is vary between 11 mg/l until 249 mg/l, different with MODIS derived TSM that distribute in range of 65 mg/l until 137 mg/l. TSM derived from MODIS is over estimated about mg/l. Research of sediment transport in coastal region should consider bathymetrical survey to observe dept of the sea which is as dominant factor of sediment transport calculation. Bathymetrical survey performed in parallel form with shoreline in a measured distance or in specific dept that planned before. Using Echo Sounder GPS Map, bathymetrical condition of Porong region had observed and displayed in figure. 8.
18 Figure.8 Bathymetrical condition of Porong region As shown in figure.8. bathymetrical condition of Porong region is shallow water with dept in range of 0.5 m 5 m. this condition affected to reflectance of water body especially in band 1 of MODIS data that used to derive TSM in coastal area. Numerical simulation of hydrodynamic model and sediment transport in Porong region displayed in figure 9 figure 12 as follow : Figure.9. Current pattern in Porong region during ebb condition.
19 Figure. 10 Current pattern in Porong region during flood condition. Figure 11. Sediment transport in Porong region during ebb condition Figure 12. Sediment transport in Porong region during flood condition
20 Based on numerical simulation as shown in above figure, it is revealed that current pattern of Porong region is continuously change the direction according to tide in this area. During this simulation it is assumed that dept of the sea is stable, and there are no significant change in boundary condition of land and water according to low and high tide. During ebb condition, current of Porong region flow downstream, while during flood condition is upstream. However in all condition, generally component current pattern of Porong region flow southward, it is the reason why current from Porong river flow southeastward with velocity up to 1.0 m/s, while velocity of current in coastal region is less than that or about 0.4 m/s. Pattern of current in this area affected sediment transport sourced from Porong river. In this simulation, source of sediment assumed only material from Porong river, while other source of sediment such as resuspension of bottom material is not calculated. Based on simulation result, it is explained that distribution of sediment affected by tidal current. During flood condition where tidal current is upstream, sediment transport is blocked in mouth of Porong river. On the other side during ebb condition where tidal current is downstream, sediment transport get maximum velocity and distribution. Also we found that concentration of TSM rapidly decrease during channeled from the source of mud volcano to coastal area as shown in figure.11 and figure.12 represented by red color to blue color. Conclusion Based on the result of this research, the conclusion can be suggested as follows: 1. Total suspended mater of Porong region is vary in the range of mg/l, and affected by rainfall according to monsoon. During northwest monsoon TSM was higher than it in southeast monsoon. Generally TSM in Porong region had not yet significantly increase caused by mud volcano as found in processed satellite data in 2006 before mud volcano occurs, 2007 and 2008 after that event.
21 2. Current pattern of Porong region is continuously change the direction according to tide in this area. During ebb condition, current flow downstream, while during flood condition is upstream. Generally component current pattern of Porong region flow southward with velocity up to 1.0 m/s, while velocity of current in coastal region is less than that or about 0.4 m/s. 3. Distribution of sediment affected by tidal current. During flood condition sediment transport is blocked in mouth of Porong river. During ebb condition sediment transport get maximum velocity and distribution. Reference Kutser, T., Metsamaa, L., Vahtmae, E., and Aps, R. (2007). Operative Monitoring of the Extent of Dredging Plumes in Coastal Ecosystems Using MODIS Satellite Imagery. Journal of Coastal Research. SI 50 page Miller, R. L,. & McKee,B. A. (2004). Using MODIS Terra 250 m imagery to map concentrations of total suspended matter in coastal waters. J. Remote Sensing of Environtment. Volume 93 Issues 1-2 Pages NASA, (2008). About Modis. Retrieved February 16, Website : Priyono, B., Sidik, F., Yunanto, A., Nugroho, Y., Mahabror., Aplikasi Teknologi Pemantauan Pencemaran Daerah Pesisir Kasus Lumpur Sidoarjo. Balai Riset dan Observasi kelautan, Departemen Kelautan dan Perikanan Wikipedia, (2008). Sidoarjo Mud Flow. Retrieved Juny 23, Website : Zhou, W., Wang, S., Zhou,Y. & Troy A. (2005). Mapping the concentrations of total suspended matter in Lake Taihu, China, using Landsat-5 TM data. International Journal of Remote Sensing Volume 27, No. 6, March 2006, Page