Mapping and measuring the quality, quantity and rate of sedimentation are essential to scientists and decision makers and for defining future land use of sensitive areas. They are also necessary for identifying areas of potential damage, sediment removal and siltation. Such techniques would be integral to identifying the processes of excessive sedimentation changes in a particular area.

Subject areas indicated for monitoring are:

· river bed load and suspended sediment load

· silt levels of dams and irrigation networks

· river bank stability

· flooding regime

· shoreline sediments of coasts

· vegetation cover

• floral and faunal vegetation indicators

CONTENTS

1. Models

2. Remote Sensing

3. Geographical Information Systems (GIS)

Models

Models are frequently used to assess and control marine pollution and provide a quantitative estimate of a particular impact. They predict the behaviour of a system based upon the mathematical laws controlling the system and its output. The use of models is of prime importance when monitoring is not possible, practicable or inadequate. The main drawback of models is a possible lack of accuracy in the predicted results. Therefore, models require validation through field measuring on a regular basis.

For example, in order to validate a runoff model, discharge data from the Rio Grande, Belize, was compared to predicted data. There was found to be a tight fit but the model tended to underestimate runoff during the dry season and overestimate it at the early stages of the wet season. Peak discharges associated with storm events were also not evident within the model. These are areas in which the model could be improved.

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Remote sensing is a tool useful especially when monitoring is not possible or is costly and intensive. It is the measurement of reflected/emitted radiation of a particular variable/target. Sedimentation studies lend themselves to this method since sediment loads are one of the more easily detectable analytes. Pigment concentrations (yellow substance) are important indicators of water quality. See the table below for details of aircraft and satellite sensors.

Table of Satellite and aircraft sensors.

See Further Information on Remote Sensing for sensor utilization.

Geographical Information Systems (GIS)

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The GIS tool is a digital mapping system based on databases, where the data is spatially indexed (geo-referenced). It is a tool especially valuable in coastal management due to the following properties:

• allowing for the analysis of scattered data from varied sources;
• enhancing the understanding of interactions between ocean-land interactions;
• performing sophisticated modelling, statistical and impact analyses;
• utilizing remotely sensed data efficiently; and
• pollution monitoring.

Many agencies, such as UNEP, FAO and most research institutions now utilities GIS with particular reference to coastal resources and management. For example, the US Fish and Wildlife Service has produced a wetland inventory. Digital atlases on a global scale are now essential to most environmental agencies.

GIS programs are now available as desktop versions which are PCs and Macintosh compatible. Thus, training for managers is still required but the system is now more accessible.