Satellite-Based Mitigation and Adaptation Scenarios for Sea Level Rise in the Lower Niger Delta

Zahrah Musa, Zahrah Naankwat Musa

• Publisher: CRC Press
• Year: 2018
• eBook ISBN: 9780429884108
• Topic: Biological Sciences
• Subtopic: Environmental Science
• Index: Biological Sciences

The Niger delta with its gentle slope and low elevation is extremely sensitive to effects of climate change. Its adaptive capacity is the second lowest in terms of socio-economic development in Nigeria. Quantitative studies on developing measures for coastal planning and management in the lower Niger delta have been limited by data availability and inaccessibility of parts of the delta. The use of satellite data can help bridge the data gap by providing ancillary data (imagery, elevation, altimetry etc.) that can be used to quantify the effects of SLR in the Niger delta. This thesis uses satellite data as the main source for hydrodynamic modelling and GIS analysis. Until recently such data might not have the accuracy and precision of directly measured data. However recent innovative approaches have enabled better exploitation of satellite data to overcome these limitations and produce adequate results to assess the impact of SLR on the Niger delta in an integrated way that will lead to practical recommendations for adaptation. Using projected global eustatic SLR values in combination with land subsidence, this thesis estimated SLR levels for the Niger delta and its effect on inundation areas and flood extent. The results indicate that the Niger delta is very vulnerable to inundation and that even minimal SLR will affect flooding in the lower Niger delta since the area continues to subside. A new coastal vulnerability index was developed in this thesis by evaluating physical, social and human influence indicators of exposure, susceptibility and resilience. The results show that parts of the Niger delta are highly vulnerable to SLR and need adequate mitigation/adaptation measures to protect them. It is recommended that sustainable local resilience practices already being used in parts of the Niger delta should be included in adaptation planning.

Table of contents

Summary

1 Introduction

Problem statement

1.1 Study aims and objectives

1.2 Scope

1.3 Thesis structure

2 Background, Study area and Data availability

2.1 Adaptation and Mitigation strategies applied on coastal areas around the world

2.1.1 West coast of Africa

2.1.2 The Netherlands

2.1.3 Bangladesh

2.1.4 Louisiana (USA)

2.1.5 The study area

2.2 Coastal protection for the Niger delta

2.3 Available Data

2.3.1 Measured discharge data for Lokoja upstream of the Niger delta

2.3.2 SRTM DEM

2.3.3 2007 Flood map

2.3.4 Shape files of: contours, state boundaries, Local Government areas, towns and settlements, rivers and streams (Nigeria, built up areas (2008)

2.3.5 Satellite imagery

2.3.6 Dredging data on the Niger River

2.3.7 Topographic data for parts of Eastern Niger delta

2.3.8 Niger Delta Regional Master Plan, Environment and Hydrology report

2.3.9 Socio-economic data (population, water supply/demand, available water resources)

3 Extracting information from modern data sources

3.1 Introduction

3.2 Overview of satellite data applications for surface water studies

3.2.1 SAR data applications

3.2.2 Satellite altimetry data applications

3.2.3 Optical satellite data

3.2.4 Satellite-derived DEM data applications

3.2.5 Gaps and limitations

3.2.6 Current data use strategies

3.3 Use of high resolution insitu sampling

3.3.1 Available data

3.3.2 Utilizing dredging data for river cross section extraction and modelling

3.4 Future direction

3.5 Conclusion

4 Modelling complex deltas in data scarce areas

4.1 Effects of river flooding on coastal areas under sea level rise conditions

4.1.1 Methodology

4.1.2 Results and Discussion

4.2 Effects of coastal flooding

4.2.1 Methodology

4.2.2 Model results

4.3 Conclusion

5 Vulnerability to sea level rise

5.1 Vulnerability assessment methodology

5.2 Selected indicators for Exposure

5.2.1 Topography

5.2.2 Coastal Slope

5.2.3 Geomorphology

5.2.4 Relative Sea Level Rise

5.2.5 Annual Shoreline Erosion Rate

5.2.6 Mean Tidal Range

5.2.7 Mean Wave Height

5.2.8 Population Density

5.2.9 Proximity to Coast

5.3 Selected indicators for Susceptibility and Resilience

5.3.1 Type of Aquifer

5.3.2 Aquifer Hydraulic Conductivity

5.3.3 Reduction in Sediment

5.3.4 Population Growth Rate

5.3.5 Ground Water Consumption

5.3.6 Emergency Services

5.3.7 Communication Penetration

5.3.8 Availability of shelters

5.4 Results and discussion

5.5 Conclusion

6 Resilience to sea level rise

6.1 Methodology

6.1.1 Date preparation: GIS data processing

6.1.2 Analysis of topography and slope

6.1.3 Mapping SLR inundation

6.2 Results

6.2.1 Local response strategies in the Niger delta

6.2.2 Inundation mapping

6.2.3 Physical characteristics of the Niger delta

6.3 Discussion of results as they relate to local adaptation practices in the Niger delta

6.4 Conclusion

7 Mitigation and adaptation to sea level rise

7.1 Mitigation and Adaptation options for deltas

7.2 Options for the Niger delta

7.2.1 Scenarios for mitigation/adaptation

7.2.2 Implementation Criteria

7.2.3 Coverage area and planning extent

7.2.4 Effects of measures on the study area

7.3 Cost of implementation

7.4 Conclusion

8 Conclusions and Recommendations

8.1 Conclusion

8.1.1 How can satellite data be applied in hydrological studies in delta areas?

8.1.2 With recent increase in flooding, will sea level rise exacerbate the effects of river flooding? What is the effect on surface water?

8.1.3 What is the effect of sea level rise on coastal flooding and inundation?

8.1.4 How much of the land can be lost to inundation?

8.1.5 How can the vulnerability of deltaic coastlines to sea level rise be evaluated?

8.1.6 What should be considered in planning for SLR adaptation? Are there existing sustainable options that can be used?

8.1.7 What are the possible effects of mitigation/adaptation options on SLR impacts on the Niger delta?

8.2 Recommendations

8.3 Study Limitations

Appendices

References

Acknowledgments

About the Author

1

Introduction

Within the last few decades the atmospheric and sea surface temperatures have been rising and climates worldwide are changing (Figure 1.1). Climate change has resulted from an accelerated increase in carbon dioxide and other greenhouse gas concentrations in the atmosphere (Williams & Ismail, 2015). Increase in sea surface temperatures cause thermal expansion, which increase the water level of the sea surface (IPCC, 2013) and as a result the shoreline moves further inland. The warming of the atmosphere causes melting of mountain glaciers and polar ice sheets, thus increasing the rise in sea levels. Based on historical data eustatic sea level changes between 1950 and 2009 were on average 1.7mm/year. In recent years satellite altimetry measurements (between 1993 and 2003) have shown an increase in sea level rise rates to over 3mm/year (IPCC, 2007a). Over the years scientists have used climate models to project possible sea level rise (SLR) levels for the future. These projections are based on scenarios to predict possible conditions of climate change and the states of the coastal areas. In its reports the Inter-governmental Panel on Climate Change (IPCC) had projected a rise of 0.18-0.5 m by the year 2100 (IPCC, 2013). This projection had its limitation due to uncertainties in response of the ice sheets, and their effect on the global sea level. Other projections of higher rise in sea level (e.g. Rahmstorf, 2007; Pfeffer, et al., 2008) were made after the IPCC (2007) report. As data became available, the IPCC revised its projections. Based on greenhouse gas emissions scenarios (known as Representative Concentration Pathways or RCPs), the IPCC projects that sea levels will rise by 0.28-0.98 m by the year 2100 (IPCC, 2013).

Climate change is a factor that will modify existing hazards and introduce new ones (Bogardi, Villagran, Birkmann, & Renaud, 2005). Natural disasters have become more frequent in coastal areas and barrier islands and river deltas are experiencing accelerated erosion, flooding and marine transgression (Williams & Ismail, 2015). In the Mediterranean region for example, the effects of climate change observed are: decrease in the total amount of precipitation; increase in the number and intensity of extreme events such as floods and droughts; and a change in the seasonal distribution of precipitation (European Environment Agency (EEA), 2012). Along the west African coast, sea levels rise trends showed over 3mm/year from 1993 to 2010 (ESA, Space in Images: mean sea level trends, 2012).

Rise in sea levels has various consequences for low lying coastal areas such as inundation due to coastal flooding by incoming rivers and/or the sea; erosion; displacement of coastal wetlands; and inland intrusion of sea water (IPCC, 2007b; Van, et al., 2012). Furthermore, SLR will reduce the availability of fresh water for human consumption, and affect the fresh water habitat of fishes and other aquatic fauna and flora.

The effects of sea level rise (SLR), however, will not be uniform all over the world but will depend on the physical, socio-economical, and anthropogenic conditions of the coastal area. Consequently some areas will experience higher and more rapidly rising sea levels than others. Relative sea level rise is the change in sea levels relative to the land elevation and includes land vertical movement in addition to global sea level rise values. Relative sea level rise values are therefore higher in subsiding coasts like river deltas than the stable coastal areas.

Coastal delta landforms are formed by the combination of river flow, tides and waves; so that the dominant process determines the characteristic of the particular delta (Nicholls, Wong, Burkett, & Codi, 2007). Fluvial deltas depend on sediment supply from upstream rivers, while Marine dominated deltas are shaped by marine processes of tide and waves. Deltas are usually very rich in biodiversity and are known to expand with increased activity upstream like agriculture and land clearing which loosen the soil adding to amount of sediment transported downstream (Mcmanus, 2002).

Some deltas like the lower Niger delta are also rich in oil and gas (and other mineral resources) making them economically very important to their countries. Coastal deltas are susceptible to subsidence when there is reduction in sediment supply (Wesselink, et al., 2015), and water or hydrocarbon extraction from underground sources (Ericson, Vorosmarty, Dingman, Ward, & Meybeck, 2006). As hydrocarbon/water is extracted, the soil compacts to fill the void and land levels lower; as long as there...

Table of contents

• Cover
• Halftitle Page
• Title Page
• Copyright
• Dedication
• Summary
• Samenvatting
• Table of Contents