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Numerical Modelling Approach for the Management of Seasonally Influenced River Channel Entrance

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Numerical Modelling Approach for the Management of Seasonally Influenced River Channel Entrance Numerical Modelling Approach for the Management of Seasonally Influenced River Channel Entrance Michael T. W. TAY Numerical Modelling Approach for the Management of Seasonally Influenced River Channel Entrance by Michael T.W. Tay Thesis Submitted in partial fulfilment of the requirements for the award of the degree of Doctor of Philosophy of the University of Portsmouth. 2018 i Abstract The engineering management of river channel entrances has often been regarded as a vast and complex subject matter. Understanding the morphodynamic nature of a river channel entrance is the key in solving water-related disasters, which is a common problem in all seasonally influenced tropical countries. As a result of the abrupt increase in population centred along coastal areas, human interventions have affected the natural flows of the river in many ways, mainly as a consequence of urbanisation altering the changes in the supply of sediments. In tropical countries River channel entrances are usually seasonally driven. This has caused a pronounced impact on the topography of river channel entrances especially in the East Coast of Borneo which is influenced by both North East (NE) and South West (SW) monsoons on top of related parameters such as waves and tides, sedimentation as well as climate change. Advanced numerical modelling techniques are frequently used as a leading approach to investigate the complicated nature of river channel entrances to represent the actual conditions of a designated area. Furthermore, the conventional ‘command and control’ approach of river channel entrance management has largely failed in this region due to the lack of process- based understanding of river channel entrances. This research focuses on creating a mesoscale numerical modelling method by integrating a reductionist and reduced complexity model approach, along with local seasonal conditions to represent the Petagas River channel entrance in demonstrating an actual river channel entrance. In assisting the modelling method, data and data- driven analysis is emphasised because the available resources and the subsequent adopted management strategies in solving these problems varies from country to country. The Petagas River channel entrance model is established with a set of numerical equilibrium equations and calibrated parameters to reflect the features of regional conditions with the combination of local validated modelling parameters. The model accurately represents the effects of both NE and SW monsoons in terms of hydraulics and sediment dynamics at the Petagas River channel entrance, as verified by site data and satellite imagery. The validated model serves as a predictive tool to evaluate various management solutions, which eventually helped in proposing the most viable solution. The proposed management solution includes a training channel and a breakwater resulting in an improved flushing capacity, thus preventing sedimentation and upstream flooding, allowing proper navigation through the river. This adopted solution is in accordance with local regulations and management plans that the local government adopt. In conclusion, the accurate investigational result from this numerical model successfully demonstrates its scientific role in solving problems related to a dynamic river channel entrance, and can serve as a numerical modelling approach for solving similar river channel entrance problems especially in tropical countries with predominant inter-annual seasonal variations. i Declaration Whilst registered as a candidate for the above degree, I have not been registered for any other research award. The results and conclusions embodied in this thesis are the work of the named candidate and have not been submitted for any other academic award. ii List of Tables TABLE 1.1 CHARACTERISTICS OF DELTAIC DEPOSITIONAL SYSTEMS (GALLOWAY 1975) ........................................................ 3 TABLE 5.1 CONSTITUENT ANALYSIS FOR KOTA KINABALU PORT BASE IN MALAYSIA TIDE TABLE 2010 (DEPARTMENT OF SURVEY AND MAPPING MALAYSIA, 2010) .............................................................................................................. 78 TABLE 5.2 TIDAL PLANES FOR KOTA KINABALU PORT (DEPARTMENT OF SURVEY AND MAPPING MALAYSIA, 2010) ................. 78 TABLE 5.3 RMSE WATER LEVEL COMPARISON TO KOTA KINABALU TIDAL STATION .......................................................... 97 TABLE 5.4 RMSE WATER LEVEL COMPARISON TO KOTA KINABALU TIDAL STATION .......................................................... 97 TABLE 6.1 ROOT MEAN SQUARE ERROR (RMSE) OF SIMULATED AND MEASURED CURRENT SPEED, DIRECTION AND WATER LEVEL. ......................................................................................................................................................... 118 TABLE 6.2 EXTREME STORM SURGE LEVEL (ABOVE MSL) CORRESPONDING TO 2, 5, 10, 50 AND 100 YEARS RETURN PERIODS FOR EXISTING CONDITIONS AT SELECTED LOCATIONS. .......................................................................................... 134 TABLE 6.3 OFFSHORE DESIGN WAVE CONDITIONS BASED ON GROW WAVE DATA ........................................................... 136 TABLE 6.4 EXTREME WAVE SETUP (ABOVE MSL) CORRESPONDING TO 2, 5, 10, 50 AND 100 YEARS RETURN PERIODS FOR EXISTING CONDITIONS AT SELECTED LOCATIONS. .......................................................................................... 138 TABLE 6.5 RECOMMENDED DESIGN WATER LEVEL (ABOVE MSL) AT BREAKWATER ENTRANCE. ........................................... 139 TABLE 6.6 RECOMMENDED DESIGN WATER LEVEL (ABOVE MSL) AT END OF TRAINING WALLS. .......................................... 139 TABLE 6.7 SIGNIFICANT WAVE HEIGHTS FOR DESIGN DETERMINED AT BREAKWATER ENTRANCE AND END OF TRAINING WALLS. 140 iii List of Figures FIGURE 1.1 TRIANGULAR CLASSIFICATION OF DELTAIC DEPOSITIONAL SYSTEMS (MODIFIED AFTER GALLOWAY (1975)). ............... 2 FIGURE 2.1 BASIC WAVE NOMENCLATURE (SAWARAGI, 1995). ...................................................................................... 8 FIGURE 2.2 WAVE CLASSIFICATION BY FREQUENCY (AFTER KINSMAN, 1965) ..................................................................... 9 FIGURE 2.3 FACTORS AFFECTING WIND WAVE DEVELOPMENT (BROOKS/COLE, 2002) ....................................................... 9 FIGURE 2.4 WAVES ENTERING SHALLOW WATER (SVERDRUP & ARMBRUST, 2009) ......................................................... 10 FIGURE 2.5 WAVE REFRACTION DIAGRAM (BROOKS/COLE, 2002) ................................................................................. 11 FIGURE 2.6 WAVE REFRACTION DIAGRAM (CEM, 2006) ............................................................................................. 12 FIGURE 2.7 WAVE DIFFRACTION PATTERNS AROUND BREAKWATERS (JOHNSON, 1951) ...................................................... 13 FIGURE 2.8 TYPES OF WAVE BREAKING (SARPKAYA & ISAACSON, 1981) ........................................................................ 14 FIGURE 2.9 APPLICATION OF VARIOUS WAVE THEORIES (LE MÉHAUTÉ, 1976) ................................................................ 16 FIGURE 2.10 MODELLING APPROACH FRAMEWORK FOR THE SIMULATION OF A RIVER CHANNEL ENTRANCE. ........................... 22 FIGURE 2.11 DEFINITIONS OF CONTROL VOLUMES FOR CELL CENTRED FINITE VOLUME METHOD IN QUADRANGULAR AND TRIANGULAR MESH ............................................................................................................................ 29 FIGURE 2.12 EXAMPLE OF MODELLED PHYSICAL PROCESSES (DHI C, 2012) ..................................................................... 32 FIGURE 2.13 MANAGEMENT UNIT C5-19 EXTRACTED FROM ........................................................................................ 36 FIGURE 2.14 COASTAL PROTECTION CONSTRUCTED BY LOCAL RESIDENTS MADE OUT OF USED TYRES ................................... 37 FIGURE 2.15 ARMOURED ROCK REVETMENT (SNH, 2000A). ...................................................................................... 39 FIGURE 2.16 TETRAPOD REVETMENT (PATEL, 2015). ................................................................................................. 40 FIGURE 2.17 TIMBER REVETMENT -BREASTWORK (SNH, 2000B) ................................................................................. 40 FIGURE 2.18 TYPICAL COASTAL REVETMENT CROSS-SECTION (PILE BUCK, 2014) ............................................................. 41 FIGURE 2.19 EROSION OCCURRENCE AT ADJACENT DUNE FRONT AS A RESULT OF THE CONSTRUCTION OF COASTAL STRUCTURE 42 FIGURE 2.20 REVETMENT CONSTRUCTION USING LORRY AND EXCAVATOR (VARELA, 2016). ............................................. 44 FIGURE 2.21 REVETMENT CONSTRUCTION USING BARGE AS TRANSPORT (ARENA KISH, 2015). ......................................... 44 FIGURE 2.22 RUBBLE MOUND BREAKWATER IN CIVITAVECCHIA (ITO, 1969) .................................................................. 45 FIGURE 2.23 OVERVIEW OF BREAKWATER ARMOUR UNITS (MUTTRAY & REEDIJK, 2009) ................................................. 46 FIGURE 2.24 RUBBLE MOUND/GRAVITY BREAKWATER (ZABEZ, 2015) .......................................................................... 47 FIGURE 2.25 VERTICAL BREAKWATER (ZABEZ, 2015). ................................................................................................ 48 FIGURE 2.26 CURTAIN WALL BREAKWATER (EVANS, 1955). ...................................................................................... 48 FIGURE 2.27 SHEET PILE BREAKWATER (EVANS,
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