Engineering for Coastal Ecosystems

Engineering for Coastal Ecosystems

Engineering for Coastal Ecosystems

Ghanshyam Bandopadhyay

Engineering for Coastal Ecosystems

Ghanshyam Bandopadhyay

ISBN - 9789361521959

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Preface

Coastal System Engineering is a part of Civil Engineering that deals with the constructions at or near the coast and also the development of the coast itself. It was concerned with the sciences of oceanography as well as coastal geology. Apart from that, Coastal Engineers were responsible for integrated coastal zone management because of their specification on hydro and morpho-dynamics of the coastal system. The specific challenges of coastal engineers are waves, storm surges, Sea level changes, and tides produced by the environment in the coastal areas.

The wide range of opportunities as a civil or environmental engineer in a range of settings involving systems and infrastructure in the coastal zone, including municipal and government authorities, water supply and management agencies, construction companies, natural resource management organizations, consulting engineering companies, airport authorities, mining companies, irrigation authorities, research organizations, and education organizations.

An approach of systems is to understand the coastal mechanisms and to solve the issues as the coastal areas are a complex type of thing. To steer the development sustainably, it requires spatial planning and management. In an applied sense, however, there is a prominent focus on the intermediate changes of the coastline. Both coastal development and coastal behavior are increasingly affected by human impact.

Table of Contents

1 Introduction to Coastal Engineering 1

1.1 Introduction 1

1.2 Engineering Aspects of Coastal Process 14

1.2.1 Profile of Coastal Zones 15

1.2.2 Waves, Tides, and Currents 18

1.2.3 Coastal Geomorphic Processes 20

1.2.4 Erosional Landforms 22

1.2.5 Depositional Landforms 23

1.3 Introduction to Ocean Engineering 28

1.4 Coastal Hydrodynamics 38

1.5 Exercise 52

2 Coastal Structures 54

2.1 Introduction 54

2.1.1 Sea Dikes 54

2.1.2 Seawalls 54

2.1.3 Revetments 55

2.1.4 Bulkheads 55

2.1.5 Groins 56

2.1.6 Detached Breakwaters 58

2.1.7 Reef Breakwaters 60

2.1.8 Submerged Sills 60

2.1.9 Beach Drains 60

2.1.10 Beach Nourishment and Dune Construction 61

2.1.11 Breakwaters 61

2.1.12 Floating Breakwaters 62

2.1.13 Jetties 63

2.1.14 Training Walls 63

2.1.15 Storm Surge Barriers 63

2.1.16 Pipelines 64

2.1.17 Pile Structures 64

2.1.18 Scour Protection 65

2.2 Fluid Mechanics in Natural Environments 66

2.3 Principles of Physical Oceanography 71

2.3.1 Physical Oceanography 72

2.3.2 Chemical Oceanography 72

2.3.3 Biological Oceanography 73

2.3.4 Geological Oceanography 73

2.3.5 Essential Aspects of Physical Oceanography 73

2.3.6 Historical Explorations 74

2.3.7 The Physical Setting 74

2.4 Marine Sediment Transport 77

2.5 Exercise 80

3 Geospatial Modeling and Analysis 81

3.1 Introduction 81

3.1.1 Analog and Digital 84

3.1.2 Discrete and Continuous 87

3.1.3 Individual and Aggregate 88

3.1.4 Agent Based Models 89

3.1.5 GIS and Time 92

3.1.6 The Value of Modeling 93

3.1.7 Model Sharing 94

3.1.8 Modeling Software 95

3.1.9 Calibration and Verification 97

3.2 Advanced Geospatial Modeling with Open Source GIS 98

3.3 Computational Fluid Mechanics and Heat Transfer 105

3.4 Turbulence 108

3.5 Exercise 118

4 International R&D Management 120

4.1 Coastal Zone Management 120

4.2 Coastal Zone Law 126

4.3 Port Planning and Policy 132

4.3.1 The port of Catania (Italy) 136

4.3.2 The port of Koper (Slovenia) 137

4.4 Marine Pollution Policy 140

4.4.1 The Act to Prevent Pollution from Ships (APPS) ) 141

4.4.2 Marine Debris Research, Prevention, and

Reduction Act (MDRPRA) 141

4.4.3 Shore Protection Act (SPA) 141

4.4.4 Marine Protection, Research, and

Sanctuaries Act (MPRSA) 141

4.4.5 The Beach Act of 2000 142

4.5 Exercise 142

5 Remote Sensing in Natural Resources Mapping 144

1.1 Introduction 144

5.1 Methodology 146

5.1.1 Input data 146

5.1.2 Data Processing 146

5.1.3 Data Interpretation 146

5.1.4 Field Verification and Data Collection 146

5.1.5 Finalization of Maps 147

5.2 Concepts of GIS and Remote Sensing in

Environmental Science 159

5.3 Numerical Models and Data Analysis in Ocean Sciences 174

5.4 Numerical Models and Data Analysis in Ocean Sciences 185

5.5 Modern Oceanographic Imaging and Mapping Technique 196

5.6 Exercise 207

6 Foundations of Restoration Ecology 208

6.1 Salt Marsh Ecology 216

6.2 Applied Coastal Ecology 225

6.3 Exercise 234

Appendix 235

Glossary 236

Index 239

Chapter - 1 Introduction to Coastal Engineering

1.1 Introduction

Coastal engineering is the study of the natural processes in and anthropogenic impacts on our beaches, inlets, estuaries, and coastal communities. The educational aim of this program is to prepare students with a broad range of engineering skills and knowledge to meet the evolving challenges in design, planning, and management in coastal waters and wetlands. Students in the graduate program can focus on the principal areas of coastal engineering, environmental fluid mechanics, estuary and marine hydrodynamics, sediment processes and morphodynamics. Students and faculty are researching the prediction of coastal hazards like storm-induced flooding and pollutant transport, the transport and mixing processes in estuaries and sounds, and the short- and long-term evolution of coastal landforms.

Coasts are functional interfaces where land, sea, and atmosphere meet. The various natural coastal processes appear to be interlinked to a greater or lesser degree, and their study requires a systems approach. This is enhanced by increasing human impact. The boundaries of the coastal system, in the longshore direction as well as cross-shore, are not established. They usually depend on the spatial and temporal scale of the coastal problem to be studied. The interaction between coastal processes and landforms takes place within a morphodynamic system. An external input of energy (e.g., tides, wind) causes water masses to move (e.g., currents, waves) and, if critical boundaries are surpassed, leads to the transport of material (e.g., silt, sand, organic matter). This results in erosive or accretional changes in the morphology, and these morphodynamic changes will have feedback on the system. Negative feedback stabilizes the morphology. Positive feedback causes instability for a relatively short period. In the long run, dynamic systems tend toward stability. In practice, the application of the coastal systems approach has not been successfully utilized. This is mainly due to the complexity of the coastal system. This complexity increases with the scale. Crucial in this approach is the indication of the smallest functional coastal unit. In a case study, the establishment of the smallest functional coastal unit is demonstrated for a relatively simple coast. The coastal development at three different scales is explained. It appears that every higher scale level is characterized by a specific steering mechanism that influences the sedimentation/erosion balance in the underlying coastal units.

The coast is the transition zone between land and sea. Its geomorphology is mainly determined by fluid dynamic processes, acting on a preexisting, sometimes (partly) relict morphological pattern. The resulting morphodynamics involves the complex mutual adjustment of processes and forms. Therefore, the coast is considered a morphodynamic system. A systems approach is needed to understand their mechanism(s) and to solve coastal problems. The human impact on the coastal environment enforces this approach. This impact is especially important in the case of low-lying coastal areas, which throughout history have been attractive residential areas. These areas have become densely populated and will increasingly do so. About 60% of the world’s population lives within 60 km of the sea, and this figure is likely to grow to 75% in the year 2015. Sixteen of the twenty-three mega-cities are situated on the coastal belt. There is increasing competition for diminishing space and resources in the coastal area. Human impacts like coastal defense, harbor and industrial activities, infrastructure, fisheries, agriculture, and the tourist industry place great pressure on coastal environments. It is, therefore, inevitable that these areas require spatial planning and management in order to steer their development sustainably. The best way to do this is through an integrated systems approach, taking the natural coastal morphodynamic system and the related coastal ecosystems into account and related socioeconomic and cultural systems.

Coasts are complex areas characterized by land-sea interaction. On a short timescale, viewed from the sea landward, a coast is affected by hydrodynamic processes produced by tides, currents, waves, and winds that, depending on a number of seawater characteristics (e.g., salinity, temperature) and on the availability of sediment, result in coastal erosion or accretion. The land, due to the geological setting, the lithology, and paleo-relief, resists the hydrodynamic processes. Moreover, fluvial, and to a lesser extent, eolian, gravitational, and even glacial transported sediments, are supplied to coastal waters from the land side. Wildlife and vegetation sometimes contribute substantially to coastal development. On larger temporal scales, however, other forces are important, as, for example, the changing position of the sea level about the land due to, among other things, changes of the global climate, resulting in an absolute (= eustatic) sea-level rise or sea-level fall. And when a landmass is uplifted or subsiding, we deal with a relative sea-level rise or fall.

Fig. 1.1 Coastal Engineering

Image Source: cae.wisc.edu

Link: http://homepages.cae.wisc.edu/~chinwu/CEE514_Coastal_Engineering/2005_Students_Web/Sylvia/introduction.htm

The cross-shore dimension of the coast is difficult to define precisely because in landward as well as in the seaward direction, the border of the coast is variable. It mainly depends on the spatial and temporal scales at which the coast is considered. In a study of actual coastal changes in the Netherlands, for instance, the coast usually includes the zone of active morphodynamics, which for practical reasons extends from approximately 10 m water depth towards the landward boundary of the coastal dunes. A study of Quaternary coastal evolution, however, involves the limits between which coastal processes have been active during the various glacial and interglacial stages of this period. In this case, the whole area between the edge of the continental shelf and the landward limit of the coastal deposits and marine erosion surfaces has to be indicated as the Quaternary coastal zone.

Dynamic coastal landforms can develop on various spatial and temporal scales. In the past, attempts to distinguish between coasts at different scale levels have often been based on their geologic and/or geomorphologic development. A well-known distinction, based on (plate) tectonic and morphologic characteristics and determined by dimensions and controls, consists of three consecutive scale levels. A first-order coastal zone, with length, width, and height ranges in the order of 1000 km, 100 km, and 10 km, respectively, and controlled by plate tectonics. A second-order coastal zone, with length, width, and height ranges in the order of 100 km, 10 km, and 1 km, respectively, and controlled by erosion and sedimentation, modifying the first-order features. A shore zone, 1 to 100 km long and 10 m to 1 km wide, controlled by waves and wave-induced currents and sediment size. However, the scale is not supported by the systems paradigm, and a temporal entry is missing.

A more ambitious attempt deals with a macro-scale, related to variations in the solid boundary state of coast on a regional scale of hundreds of kilometers, and a mesoscale at the level of individual coastal compartments. In the last decades of the twentieth century, several authors postulated the relation between the spatial and temporal aspects of developing coastal features. For small-scale features, this can be easily established. The activity of short waves on sandy seabed results within a few minutes in the genesis of a wave-ripple field (with wavelengths in the order of centimeters). The formation of mega-ripples (with a length scale in the order of meters) on an inter-tidal sandbank in an estuary requires hours to days. Swash bars (which extend over hundreds of meters) need weeks to months for their development. With an increasing scale level, however, the forms increase not only in volume but also in complexity. Therefore, it is not yet possible to indicate process descriptions for the morphodynamic process–response relations at the larger spatial and temporal scales. Along the sandy coast of the Netherlands, research merely focuses on the mechanics of the cell circulation, which can be considered the most dynamic component of the Dutch coastal system. A process description of the whole coast as a coherent functional unit at different scale levels is a challenge.

When studying coastal development from a scientific point of view, the emphasis is usually on the characteristics of the final geomorphologic stage at the scale level concerned, at the expense of the intermediate characteristics. In an applied sense, however, there is a prominent focus on the intermediate changes of the coastline. Although both approaches overlap, the latter is referred to as coastal behavior to distinguish it from coastal development. Both coastal development and coastal behavior are increasingly affected by human impact.

The coastal zone is a dynamic area of natural change and increasing human use. They occupy less than 15% of the Earth’s land surface, yet accommodate more than 50% of the world population (it is estimated that 3.1 billion people live within 200 kilometers from the sea). With three-quarters of the world population expected to reside in the coastal zone by 2025, human activities originating from this small land area will impose an inordinate amount of pressure on the global system. Coastal zones contain rich resources to produce goods and services and are home to most commercial and industrial activities.

In the European Union, almost half of the population now lives within 50 kilometers of the sea, and coastal zone resources produce much of the Union’s economic wealth. The fishing, shipping and tourism industries all compete for vital space along Europe’s estimated 89 000 kilometers of coastline, and coastal zones contain some of Europe’s most fragile and valuable natural habitats. Shore protection consists of up to the ’50s of interposing a static structure between the sea and the land to prevent erosion and or flooding, and it has a long history. From that period, new technical or friendly policies have been developed to preserve the natural environment when possible. It is already important where there are extensive low-lying areas that require protection. For instance: Venice, New Orleans, Nagara river in Japan, Holland, Caspian Sea Protection against the sea level rise in the 21st century will be especially important, as the sea-level rise is currently accelerating. This will be a challenge to coastal management, since seawalls and breakwaters are generally expensive to construct, and the costs to build protection in the face of sea-level rise would be enormous. Changes on sea level have a direct adaptive response from beaches and coastal systems, as we can see in the succession of a lowering sea level. When the sea level rises, coastal sediments are in part pushed up by a wave and tide energy, so sea-level rise processes have a component of sediment transport landwards. This results in a dynamic model of rising effects with a continuous sediment displacement that is not compatible with static models where coastline change is only based on topographic data.

There are five generic strategies for coastal defense. The decision to choose a strategy is site-specific, depending on the pattern of relative sea-level change, geomorphological setting, sediment availability, and erosion, as well as a series of social, economic, and political factors. Alternatively, integrated coastal zone management approaches may be used to prevent development in erosion or flood-prone areas, to begin with. Growth management can be a challenge for local coastal authorities who often struggle to provide the infrastructure required by new residents seeking sea-change. Sustainable transport investment to reduce the average ecological footprint of coastal visitors is often a good way out of coastal gridlock.

Fig. 1.2 Coastal Engineering (construction)

Image Source: globaljournals.org

Link: https://globaljournals.org/tag/coastal-engineering

Examples include Dongtan and the Gold Coast Oceanway. Do nothing, no protection, leading to eventual abandonment – The ’do nothing’ option, involving no protection, is a cheap and expedient way to let the coast take care of itself. It consists of the abandonment of coastal facilities when they are subject to coastal erosion, and either gradually landward retreat or evacuation and resettlement elsewhere. This option is very environmentally friendly, and the only pollution produced is from the resettlement process. However, it does mean losing much land to the sea, and people will lose their houses and their homes. Managed retreat or realignment, which plans for retreat and adopts engineering solutions that recognize natural processes of adjustment, and identifying a new line of defense where to construct new defenses. Managed retreat is an alternative to constructing or maintaining coastal structures.

A managed retreat allows an area that was not previously exposed to flooding by the sea to become flooded. This process is usually in low lying estuarine or deltaic areas and almost always involves the flooding of land that has, at some point in the past, been reclaimed from the sea. Managed retreat is often a response to a change in sediment budget or sea-level rise. The technique is used when the land adjacent to the sea is low in value. A decision is made to allow the land to erode and flood, creating new sea, inter-tidal, and salt-marsh habitats. This process may continue over many years, and natural stabilization will occur. The earliest managed retreat in the UK was an area of 0.8 ha at Northey Island in Essex, that was flooded in 1991. Tollesbury and Orplands followed this in Essex, where the sea walls were breached in 1995. In the Ebro Delta (Spain), coastal authorities have planned a managed retreat in response to coastal erosion. The main cost is generally the purchase of land to be flooded. Housings compensation for the relocation of residents may be needed. Any other human-made structure which will be engulfed by the sea may need to be safely dismantled to prevent sea pollution.

In some cases, a retaining wall or bund must be constructed inland in order to protect land beyond the area to be flooded. However, such structures can generally be lower than would be needed on the existing coast. The monitoring of the evolution of the flooded area is another cost. Costs may be lowest if existing defenses are left to fail naturally. Still, often the realignment project will be more actively managed, for example, by creating an artificial breach in existing defenses to allow the sea in at a particular place in a controlled fashion, or by pre-forming drainage channels for created salt-marsh.

Human strategies on the coast have been heavily based on a static engineered response, whereas the coast is in, or strives towards, a dynamic equilibrium. Solid coastal structures are built and persist because they protect expensive properties or infrastructures, but they often relocate the problem downdrift or to another part of the coast. Soft options like beach nourishment, while also being temporary and needing regular replenishment, appear more acceptable, and go some way to restore the natural dynamism of the shoreline. However, in many cases, there is a legacy of decisions that were made in the past, which have given rise to the present threats to coastal infrastructure and which necessitate immediate shore protection. For instance, the seawall and promenade of many coastal cities in Europe represents a highly engineered use of prime seafront flange-eating space, which might be preferably designated as public open space, parkland and amenities if it were available today. Such open space might also allow greater flexibility in terms of future land-use change, for instance, through a managed retreat, in the face of threats of erosion or inundation as a result of sea-level rise. Foredunes areas represent a natural reserve that can be called upon in the face of extreme events; building on these areas leaves little option but to undertake costly protective measures when extreme events (whether amplified by gradual global change or not) threaten. A managed retreat can comprise ’setbacks,’ rolling easements and other planning tools, including building within a particular design life. Maintenance of those structures or soft techniques can arrive at a critical point (economically or environmentally) to change the adopted strategy.

• Structural or hard engineering techniques, i.e., using permanent concrete and rock constructions to fix the coastline and protect the assets locate behind. These techniques–seawalls, groynes, detached breakwaters, and revetments – represent a significant share of protected shoreline in Europe (more than 70%).

• Soft engineering techniques (e.g., sand nourishments), building with natural processes and relying on natural elements such as sands, dunes, and vegetation to prevent erosive forces from reaching the backshore. These techniques include beach nourishment and dune stabilization.

The futility of trying to predict future scenarios where there is a large human influence is apparent. Even future climate is, to a certain extent, a function of what humans choose to make of it, for example, by restricting greenhouse gas emissions to control climate change. In some cases - where new areas are needed for new economic or ecological development - a seaward move strategy can be adopted. Some examples from EROSION are Ebro delta (E), Koge Bay (DK) Western Scheldt estuary (NL), Chatelaillon (F).

There is an obvious downside to this strategy. Coastal erosion is already widespread, and there are many coasts where exceptional high tides or storm surges result in encroachment on the shore, impinging on human activity. If the sea rises, many coasts that are developed with infrastructure along or close to the shoreline will be unable to accommodate erosion,