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WP1: Simulating the Holocene development of the mixed tidal-fluvial Mahakam delta

Research group
Project leaders:
Prof. Dr. Salomon B. Kroonenberg
Dr. Jajang Sukarna

Researcher:
Dr. Rory A.F. Dalman

Other participants:
Ir. Subaktian Lubis

3. Summary of the project
This coordinating post-doc project aims to establish the impact of changes in sea-level, watershed characteristics and anthropogenic disturbances on the sedimentary and ecological dynamics of the Mahakam delta in the past 5000 years. The Mahakam delta is is a unique delta because of the strict separation of fluvial and tidal domains in the delta and the absence of large floods and hence levees and crevasse splays, and because of the dramatic ecological changes in the last decades due to the construction of shrimp ponds.
The sedimentary dynamics will be studied using novel very high resolution geophysical surveys, corings, and radiometric datings, in order to construct a 3-D conceptual sedimentary model describing the evolution of mixed tide-fluvial processes during Holocene sea-level rise. The model will be based on an innovative combination of Delft3D, a morphodynamic model that predicts the behaviour of sediment in distributaries and along delta fronts with great hydraulic accuracy but with limited time depth (decades at most) and without a vertical dimension that predicts how 3-D sediment bodies are being formed; and 3D-SEDFLUX, that simulates the building of delta architecture as a function of sea-level change, subsidence and sediment supply in geological time scales, but with limited hydraulic accuracy. The model will integrate data from other projects on smaller time scales (last 200 years, WP3), on sediment concentrations in fluvial and tidal domains captured by remote sensing imagery validated with field data (last 50 years, WP2), and on hydraulic geometry of tidal channels (WP5).
Ecological dynamics have great impact on sedimentation patterns and rate as well. Preliminary palynological data indicate a dramatic expansion of grasses due to deforestation in the upstream parts of the basin since at least 600 years ago, causing changes in sediment dynamics. The expansion of shrimp ponds also altered sedimentary conditions in the delta. The impact of anthropogenic disturbances and resulting possible flip-flop stable-state changes in the ecosystems will be monitored through stress in mangrove foliage captured by hyperspectral imaging (WP6), and by studying phytoplancton (WP7). Their impact on sedimentation conditions will be taken into account into the 3Dmodel. Ultimately, the behaviour of stakeholders in the light of the main property rights regimes in forestry and shrimp farming (WP8) will determine how anthropogenic impact will translate into future delta dynamics. Translating these choices into scenarios for the future development of the delta using the 3D model will be the ultimate output of this project.

4. Detailed description of the project
a. Scientific Background
The late-Holocene Mahakam delta, located along the tropical eastern shore of Kalimantan, Indonesia, prograded seaward about 60 km during the past 5000 years, in spite of rising sea level. The Mahakam river discharge amounts to ~4200m3/sec, and sediment output up to 20 Mt/year sediment (Syvitski et al., 2005). Tides are semi-diurnal and the tidal amplitude ranges from <1 m in neap tides to 3 m during spring tides. Local wave action is low. While the Mahakam delta is a textbook example of a mixed fluvial–tidal delta (Galloway, 1975), it is unique in the fact that fluvial and tidal depositional regimes in the delta are virtually separated. This is due to the presence of large upstream lakes; they buffer discharge peaks to such an extent that no flooding occurs in the delta (Allen & Chambers, 1998). Fluvial deposition is essentially limited to the channels of the two main delta distributaries and their mouthbars, and no levees nor crevasse splays are present. Tidal deposition predominates in the interdistributary areas. Here, mud from offshore is brought landwards along high-sinuosity tidal channels which have no connection to the fluvial distributaries. Therefore, very little mixing between fluvial and tidal sediment fluxes occurs outside the main fluvial distributaries.
Deltas are among the most complex sedimentary bodies in the world, due varying degrees of fluvial, tidal and wave action, varying drainage basin and sediment characteristics, varying offshore slope and bathymetry, sea-level and subsidence history, vegetation dynamics and anthropogenic impact Integrating delta structure and dynamics into a single 3-D depositional model has proved exceedingly difficult so far. Our best hope is to try to keep constant as many as possible of the forcing mechanisms in particular deltas in order to single out specific forcing factors. The Mahakam delta represents our best hope to single out the impact of fluvial and tidal processes separately because of the characteristics mentioned above, in the absence of wave action and fluvial discharge variations. In this aspect the Mahakam has great advantages above other well-studied tide-dominated deltas in the tropics such as the Ganges-Brahmaputra, Fly delta (Dalrymple et al., 2003), etc.
The main focus of earlier studies of the Mahakam delta has been on its sandy deposits; the mouth bar, channel and delta front as analogues of hydrocarbon bearing Miocene and Tertiary deposits in the subsurface of the Mahakam delta. However, little attention has been paid so far to the origin and distribution of fluvial deltaic facies in relation to tidal processes. (Allen et al. 1976; Allen and Mercier 1994; Allen and Chambers 1998; Gastaldo and Huc 1992; Gastaldo et al. 1995). High-resolution shallow seismic data became available in the 1990s, as the focus of research shifted to the Pleistocene and Holocene offshore deposits (Roberts and Sydow 1996; 2003; Snedden et al. 1996; Suiter 1996). Nevertheless most seismic and core data were retrieved beyond the sub-tidal zone, therefore the extension of the distribution of deltaic facies in relation to tidal- and fluvial dynamics remains unexplored.
The typical delta-front platform and slope of the Mahakam delta can be interpreted as a compoundclinoform development, also known as subaerial and subaqueous deltas formation. Few data exist on the progradation rate of the Mahakam subaqueous delta or delta-front slope (Van den Bergh, 2004), and observations from other subaqueous deltas such as the Amazon delta (Nittrouer et al. 1996), the Ganges-Brahmaputra delta (Kuehl et al. 1997), the Po delta (Cattaneo et al. 2003), suggests that the depositional regime of the subaerial delta and the subaqueous delta may be very different. Subaqueous deltas are commonly attributed to energetic marine environments (Swenson et al 2005). Based on the morphology of the subaqueous delta, a distinction can be made between the delta-front slope and the prodelta/shelf environment. Understanding deltaic evolution requires studying the relation between the subaerial and subaqueous and the associated processes forming the delta front platform and prodelta. The modern Mahakam delta has been governed by more or less the same dynamics over the last 5000 years, due to its location at the equator. Therefore, the fluvial and tidal processes that have interacted here can be considered stable for centuries back. This provides excellent conditions to study the long term delta development. 14C AMS datings of plant remains from borings in the Holocene Mahakam Delta give a preliminary approximation of the late Holocene sea level history for East Kalimantan (Storms et al. 2005), suggesting that the progradational delta system evolved under conditions of slowly rising sea level. Average deposition rates indicate that deposition may be driven by the spring-neap tide cycles instead of the daily tidal cycle, as has also been recorded in the Fly delta, Papua New Guinea (Dalrymple et al., 2003). A palynological spectrum of a core obtained during the pilot phase shows predominating rainforest elements, with an increase of mangrove (Sonneratia) elements from about 2000 BP and an increase of anthropogenic elements in the last 600 years (Van der Kaars, unpublished report).

Pollen diagram of core 12, northern Mahakam delta (S. van der Kaars, pers. comm)

Quantitative modelling of sedimentary geology has a history of over 40 years and has become indispensable for the industry and scientific communities. Numerous models, varying in applicability and functionality, have been presented over the years (Paola 2000). A next generation of numerical models of fluvial- and deltaic systems such as 3D-SEDFLUX (Hutton and Syvitski 2003) http://instaar.colorado.edu/deltaforce/workshop/presentations/syvitski_files/frame.htm is being developed to handle the complexity of three dimensional responses of sediment deposition to rising sea-level, climate, and the internal dynamics of fluvio-deltaic systems covering most of these outstanding questions. However recently Slingerland (2005) noticed that most questions are still open. An important reason is that the long-term processes governing depositional processes are still not fully comprehended (Tipper 1991).
Therefore, we intend to combine the 3D SEDFLUX model with the most advanced morphodynamic model available at present, DELFT3D, (http://www.wldelft.nl/soft/d3d/mods/sed/index.html), a numerical engineering model developed at Delft Hydraulics with proven capabilities of simulating 3D morphology and stratigraphy on smaller time scales, max 101 years. In cooperation with the section of hydraulic engineering at DUT DELFT3D is being upgraded for large time scales by introducing scaling parameters, so called morphological factor (Storms and Stive 2005, Lesser et al.,2004). This factor makes use of the predictability of sediment transport to upscale simulation time. In the case of the Mahakam delta, the absence of river floods reduces the temporal variability of sediment transport patterns in the delta, making it an ideal test case for Delft3D.

The main research questions are the following:

  1. How has delta progradation taken place in the past 5000 years against a rising sea level, and how the effects of future accelerated sea-level rise on delta development can be predicted on the basis of these data?

  2. What is the impact of rising sea level on the distribution of the fluvial and tidal regimes with respect to each other in past, present and future?

  3. What is the impact of deforestation in the upstream part of the basin on fluvial dynamics, and what is the impact of recent replacement of mangroves by shrimp ponds in the delta on the balance of fluvial and tidal sedimentation?

  4. Can we develop general rules on delta dynamics from the Mahakam delta for the development of a generic 3D model of delta evolution?

b. Specific Objective(s)
To that end, we will study the interaction between tidal and fluvial processes in distributary channels, and how their depositional patterns and stratal signatures changed as a result of sea-level rise during the late Holocene. Shallow geophysical surveys, corings, and radiometric datings will be used to construct a conceptual sedimentary model describing the evolution of mixed tide-fluvial processes in time and space. This concept will be used for the further development of the combined 3DSEDFLUX/DELFT3D model enhancing its capabilities for modelling large time scale processes and should result in simulating long term.
Data from other projects on the impact of anthropogenic disturbances and resulting possible flipflop stable-state changes in the ecosystems on sediment dynamics, such as monitored through stress in mangrove foliage captured by hyperspectral imaging (WP6), by studying phytoplancton (WP7) as well as data on hydraulic geometry upstream (WP4) and in the delta itself (WP5) will be taken in to account in the model. Ultimately, the behaviour of stakeholders in the light of the main property rights regimes in forestry and shrimp farming (WP8) will determine how anthropogenic impact will translate into future delta dynamics.

c. Workplan

  1. A detailed seismic/bathymetric survey of the delta platform in the tidal zone up into the fluvial and tidal channels using GEOMARIN II vessel of the MGI. Preliminary sparker data have already been collected in the southernmost distributary of the delta (Darlan et al., 2004), but these are of insufficient resolution to serve as a base for distinguishing the major sedimentary features in the delta prism of the last 5000 years. A very high resolution survey using the Innomar Parametric Echosounder (www.innomar.com) will be carried out on the MGI GEOMARIN II research vessel in the delta channels and over the submerged delta platform down to the 20m isobath, from where other data are available. This innovative instrument is capable of producing images of the subsurface with a resolution on dm scale. (Figure). Moreover data can be obtained at very shallow water depths (1 m). The TUDelft has recently acquired this equipment, and we have obtained imagery of unprecedented detail in the Westerschelde estuary in the Netherlands and in the Volga delta (see figure).

    Parametric echosounder profile obtained from Volga delta, Russia. Horizontal lines are 1 m apart; green line is river bottom (2-4 m water depth), red line is multiple

    The seismic data will be processed using software developed at the University of Ghent (Belgium) and commercial processing & interpretation packages. A detailed grid of 2D seismic profiles will be acquired to allow pseudo-3D interpretation of the data and should give detailed insight into the characteristics of the Holocene delta, such as thickness and depositional patterns of the various facies types.

  2. Based on the initial seismic results a number of locations will be picked to drill shallow cores to obtain a continuous section of submerged deltaic sediments. Cores will be analysed on sediment characteristics, palynology, biostratigraphy, paleo-environmental characteristic, geochemistry and chronology. Samples will be taken to assess grain size, organic content, macrofossils and 14C datings. The 14C datings will be used for the sea-level reconstruction, 210Pb data from the WP3 project will be used to determine sedimentation rate. Furthermore an onshore coring field campaign in the Mahakam delta plain down to a depth of about 8 m will be carried out, using a hand-augering device, especially from the south (fluvial dominated) and central (tidal dominated) areas of the delta in order to study the overall lateral extension of depositional environments. A differential GPS system will be used for determining the core positions and elevation.

  3. A full-fledged dating programme is proposed in order to reconstruct the first sea-level curve for East- Kalimantan in detail and to link the Holocene sea-level to changes in the depositional patterns in the delta. This is not only vital information for the description and understanding of the Mahakam delta, it also very important for the other projects of this, as well as other clusters and in general for different fields of science studying in East Kalimantan, such as growth of coral reefs and development of fishing and shrimp industry.

  4. A 3D numerical simulation of the Mahakam delta will be made using 3DSEDFLUX/DELFT3D by developing its capabilities for large times scale simulations. Identifying the proper processes and scaling factors will be done by using the interpretations of the field data that is capable of predicting the impact of coexisting tidal and fluvial processes on deltaic development for large time scales (101-105 years). Such a comparison is possible using probability output obtained with Advanced Markov Chain Monte Carlo method (Hoogendoorn and Weltje in press) instead of deterministic output.

  5. Next the model should be able to evaluate different scenarios concerning, physical, biological and societal changes, on the basis of data from other projects. For example, a scenario could comprise of an increase in sediment supply as a result of deforestation of the hinterland and predicted sea-level change as a result of global warming. Forced exogenous pressure on the ecosystems of the Mahakam delta, a consequence of industrial activities and growing population density should also be considered as they have a direct influence on sedimentation properties of the delta system.

d. Scientific Relevance
This project has the potential to combine detailed sedimentological investigation of a well constrained (in time and space) mixed fluvio-tidal delta with latest modeling developments in numerical modeling of these environments. This provides a unique opportunity where model predictions can be tested by observations.

5. Participation in a graduate School ('onderzoeksschool')
CTG (Centre of Technical Geosciences) TUDelft

6. Scientific performance of members of the research group(s)

  • Hoogendoorn, R.M., Boels, J.F., Kroonenberg, S.B., Simmons, M.D., Aliyeva, E., Babazadeh, A.D. Huseynov,D. 2005 Development of the Kura delta, Azerbaijan; a record of Holocene Caspian sea-level changes. Marine Geology 222-223, 359-380

  • Hoogendoorn, R. M. and Weltje, G. J. (in press). A stochastic model for simulating long time series of river-mouth discharge and sediment load. Flooding in Europe: Challenges and Developments in Flood Risk Management. S. Begum, J. W. Hall and M. J. F. Stive. Dordrecht, Kluwer.

  • Kroonenberg, S. B., Simmons, M. D., Alekseevski, I., Aliyeva, E., Allen, M. B., Davies, C.,Hoogendoorn, R. M., Huseynov, D., Overeem,. N., Rusakov, G. V. , Svitoch, A. A., Vincent, C., 2005. Two deltas, two basins, one river, one sea: The modern Volga delta as an analogue of the Neogene Productive Series, South Caspian Basin. Deltas. Tulsa, SEPM Special Publication. No. 83, 231-256

  • Overeem, I., Tebbens, L. A., Veldkamp, A. and Kroonenberg, S. B. (2003). Modelling Holocene stratigraphy and depocentre migration of the Volga delta due to Caspian Sea Level change. Sedimentary Geology 159(159- 175).

  • Storms, J. E. A., Hoogendoorn, R. M., Dam, M. A. C., Hoitink, A. J. F. and Kroonenberg, S. B. 2005. Late-Holocene evolution of the Mahakam delta, East Kalimantan, Indonesia. Sedimentary Geology 180, 144-156

  • Syvitski, J.P.M., Vörösmarty, C.J., Kettner, A.J., and Green, P.A., 2005. Impact of Humans on the Flux of Terrestrial Sediment to the Global Coastal Ocean. Science, V. 308, No. 5720, 376-380.

  • Darlan, Y., G.P. Yoga, D.A.S. Ranawijaya, K. Hardjawidjaksana, K. Budiono 2004 Sedimentary environments and mangrove community of the Mahakam delta. Paper workshop EKP Pilot Phase

  • Ranawidjaja, D.A.S., E.Usman, Y. Noviadi & K.T. Dewi 2004 Paleoclimatopogy and sea level changes of Mahakam Delta, East Kalimantan based on geological and geophysical integrated data. Bulletin of the Marine Geological Institute, 19(2):41-58

  • Zuraida, R., Yudhicara, and R. Rahardiawan, 2004. Holocene Biogenic Gas of Madura Strait, East Java, Indonesia. Proceeding of the International Symposium on Shallow Geology and Geophysics, April 12 – 24, Hanoi, p. 84-91.

7. Literature references

  • Allen, G. P., Laurier, D. and Thouvenin, J. (1976). Sediment distribution patterns in the modern Mahakam delta. Proceedings Indonesian Petroleum Association: 159-178.

  • Allen, G. P. and Mercier, F. (1994). Reservoir facies and geometry in mixed tide and fluvial dominated delta mouth bars: example from the modern Mahakam delta (East Kalimantan). Proceedings Indonesian Petroleum Association: 261 - 273.

  • Allen, G. P. and Chambers, J. L. C. (1998). Sedimentation in the Modern and Miocene Mahakam delta. Jakarta, Indonesian Petroleum Association. 236

  • Cattaneo, A., Correggiari, A., Langone, L. and Trincardi, F., 2003. The late-Holocene Gargano subaqueous delta, Adriatic shelf: sediment pathways and supply fluctuations. Marine Geology 193, 61-91.

  • Dalrymple, R.W., E.K. Baker, P.T. Harris, M.G. Hughes (2003) Sedimentology and stratigraphy of a tide-dominated foreland-basin delta (Fly River, Papua New Guinea). In: Tropical deltas of Southeast Asia, Sedimentology, Stratigraphy and Petroleum Geology. F. H. Sidi, D. Nummedal, P. Imbert, H. Darman and H. W. Posamentier. Tulsa, SEPM Special publication. 76: 125-145.

  • Gastaldo, R. A. and Huc, A. Y. (1992). Sediment facies, depositional environments, and distribution of phytoclasts in the recent Mahakam River delta, Kalimantan, Indonesia. Palaios 7: 574-590.

  • Gastaldo, R. A., Allen, G. P. and Huc, A. Y. (1995). The tidal character of fluvial sediments of the modern Mahakam River delta, Kalimantan, Indonesia. Tidal signatures in modern and ancient sediments. B. W. Flemming and A. Bartholoma, Special Publication International Association of Sedimentologist. 24: 171-183.

  • Hutton, E. W. H. and Syvitski, J. P. M. (2003). Advances in the numerical modeling of sediment failure during the development of a continental margin. Marine Geology 203: 367-380.

  • Hoogendoorn, R. M. and Weltje, G. J. (in press). A stochastic model for simulating long time series of river-mouth discharge and sediment load. Flooding in Europe: Challenges and Developments in Flood Risk Management. S. Begum, J. W. Hall and M. J. F. Stive. Dordrecht, Kluwer.

  • Kuehl, S.A., B.M. Levy, W.S. Moore and M.A. Allison. 1997. Subaqueous delta of the Ganges-Brahmaputra river system. Marine Geology, 144: 81-96.

  • Lesser, G.R., J.A. Roelvink, J.A.T.M. van Kester & G.S. Stelling (2004). Development and validation of a three-dimensional morphological model" Coastal Engineering, 51, 883-915.

  • Nittrouer, C.A., S.A. Kuehl, A.G. Figueiredo, M.A. Allison, C.K. Sommerfield, J.M. Rine, L.E.C. Faria, and O.M. Silveira, The geological record preserved by Amazon shelf sedimentation, Cont. Shelf Res. 16, 817-841 (1996).

  • Paola, C. (2000). Quantitative models of sedimentary basin filling. Sedimentology 47(suppl 1.): 121-178.

  • Roberts, H. H. and Sydow, J. (2003). Late Quaternary stratigraphy and sedimentology of the offshore Mahakam delta, East Kalimantan (Indonesia). Tropical deltas of Southeast Asia, Sedimentology, Stratigraphy and Petroleum Geology. F. H. Sidi, D. Nummedal, P. Imbert, H. Darman and H. W. Posamentier. Tulsa, SEPM Special publication. 76: 125-145.

  • Slingerland, R. (2005). Process-based stratigraphical modeling of fluvial systems: Why is progress so slow? Keynote lecture 8th International Conference on Fluvial Sedimentology 2005.http://www.8thfluvconf.tudelft.nl/keynotes/keynote2.html

  • Snedden, J. W., Sarg, J. F., Clutson, M. J., Maas, M., Okon, T. E., Carter, M. H., Smith, B. S., Kolich, T. H. and Yazid Manson, M. (1996). Using sequence stratigraphic methods in high-sediment supply deltas: examples from the ancient Mahakam and Rajang-Lupar deltas. Proceedings Indonesian Petroleum Association 25: 281-295.

  • Storms, J.E.A. and M.J. Stive (2005) Fluvio deltaic modeling using DELFT3D proceedings 8th International Conference on Fluvial Sedimentology 2005.http://www.8thfluvconf.tudelft.nl/

  • Suiter, S. S. (1996). Shallow 3-D seismic analysis of late Pleistocene lowstand deltas (Mahakam, Indonesia). Proceedings Indonesian Petroleum Association 25: 347-351.

  • Tipper, J. C. (1991). Modelling the fill of sedimentary basins. Exploration Geophysics 22: 397-400. Van den Bergh, G.D. 2004 Feasibility of application of high-resolution proxy studies in East Kalimantan river deltas and adjacent shelf areas, to assess natural and anthropogenically induced environmental changes. Paper EKP Pilot Phase workshop, Jakarta, May 2004

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