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NSW Coastline Management Manual

New South Wales Government
September 1990

ISBN 0730575063

Appendix B: Coastline Processes

Appendix B13 - Human Activities

1 INTRODUCTION

Human activities in the coastal zone are many and varied, e.g. the construction of coastal protection works, passive and active recreational pursuits, the use of certain areas for residential, commercial or ecological purposes, etc.

Human activities can significantly affect coastal processes. These effects can be both beneficial and detrimental. For example, consider the construction of a seawall. Benefits include the protection of properties at risk of erosion or recession hazard. Detrimental effects may include the loss of beach sand through interference with the sediment budget, more limited access to the beach and reduced recreational amenity.

"Problems" in the coastal zone are largely perceived in terms of interference with human activities. This appendix indicates possible detrimental impacts arising from various human activities. This is done through identification of the interrelationships between human activities, their impact on coastal processes and the detrimental consequences to coastal amenity.

The beneficial effects of human activities are largely ignored in the following discussion. This is not because benefits are unimportant, costs and benefits must be objectively weighed in the rational management of coastal lands, but because detrimental impacts are often ignored.

2 ACTIVITIES, IMPACTS AND CONSEQUENCES

Human activities affect coastal processes in a rich and varied way. To facilitate discussion, a three-way classification of "activities", "impacts" and "consequences""has been adopted.

Types of Activities

Three broad classes of human activities that may have detrimental impacts on coastal processes have been identified for the purposes of this analysis:

Within these broad classifications, a variety of potentially detrimental activities can be identified.

For example, the type of coastal structure will influence its impact on coastal processes; development activities such as the clearing of vegetation, earthworks, and the construction of roads all have different impacts on coastal processes; the use of coastal lands by people introduces potential problems associated with sewage disposal, vehicular traffic, boat movements, etc.

The chart of Figure B13.1 shows the different human activities with potentially detrimental impact that are considered in this analysis.

Impacts on Coastal Processes

The coastal processes or attributes that can be significantly modified by the above activities include the following:

Wave climate is discussed in Appendix B5; longshore and onshore/offshore transport are discussed in Appendix B7; vegetation is discussed in Appendix B8; sand drift is discussed in Appendix B9. Tidal prism refers to the volume of tidal water that moves into and out of estuaries and coastal lakes each tide cycle. Stormwater flows typically enter coastal waters via a creek that crosses the beach berm. Water quality has not been discussed, but is a parameter that affects the amenity and use of coastal and estuarine waters.

In general terms, human activities can either increase, reduce or disrupt the above processes. Figure B13.1 shows the specific impacts included in the present analysis.

Detrimental Consequences

As a consequence of the above impacts, the amenity and attractiveness of the coastal zone may be altered and perhaps significantly degraded. Figure B13.1 shows the detrimental consequences of relevance to this analysis. They have been classified into the following three categories on the basis of location:

3 THE INTERACTION MATRIX

Figure B13.1 shows the interrelationships between human activities, impacts and potential detrimental consequences in matrix form. The potential nature of the detrimental consequences is emphasized. The matrix is intended to alert readers to possible adverse consequences of human activities. A variety of interrelated and site specific factors determine the actual consequences that accompany human activities in the coastal zone.

Fig B13.1 interaction matrix

Figure B13.1 Interaction Matrix

Two examples illustrate how the matrix works:

First consider the clearing of dune vegetation for a coastal development. One impact of this activity may be damage to nearby vegetated areas. Possible consequences are the invasion of dune areas by exotic vegetation or dune erosion (blowouts).

Next consider the disposal of stormwater from a coastal development. This may have a number of adverse impacts on water quality, one of which may be increased nutrient levels in estuarine and coastal waters. Possible detrimental consequences include lower dissolved oxygen levels, algal blooms and the death of aquatic flora/fauna.