Introduction

This chapter deals with how human activities have changed the physical interaction between the sea and the land. This physical interaction is important because about 60 per cent of the world's population live in the coastal zone (Nicholls et al., 2007). The “coastal zone” is defined in a World Bank publication as “the interface where the land meets the ocean, encompassing shoreline environments as well as adjacent coastal waters. Its components can include river deltas, coastal plains, wetlands, beaches and dunes, reefs, mangrove forests, lagoons and other coastal features.” (Post et al., 1996) In some places, natural coastal erosion processes cause damage to property, harm to economic activities and even loss of life. In other places, human activities have modified natural processes of erosion of the coast and its replenishment, through: (1) coastal development such as land reclamation, sand mining and the construction of sea defences that change the coastal alongshore sediment transport system; (2) modification of river catchments to either increase or decrease natural sediment delivery to the coast; and (3) through global climate change and attendant sea level rise changes to surface wave height and period and the intensity and frequency of storm events.

Natural coastal erosion and property damage

Coastal erosion is a natural, long-term process that contributes to the shaping of present coastlines, but it can also pose a threat to life and property (Rangel-Butrago and Anfuso, 2009). For example, the total coastal area (including houses and buildings) currently being lost in Europe through marine erosion is estimated to be about 15 km2 per year (Van Rijn, 2011). Over 70 per cent of the world's beaches experience coastal erosion, some portion of which is a natural process (Dar and Dar, 2009). Other natural processes influencing coastal sediment dynamics include the supply of biogenic carbonate sand and gravel (see Chapter 7) and volcanism which can provide an important sediment source to some coastal areas, including some continental coasts, such as in Italy (de Rita et al., 2002) and to volcanic islands, such as in Polynesia, Indonesia, the Caribbean, the Azores and sub-Antarctic islands (e.g., Dey and Smith, 1989; Ross and Wall, 1999).