CONTENTS

1. Protection from Changes in Sediment Regimes

2. GPA Objective in resect to Sediment Mobilization

3. Proposed GPA Actions

1. Why the marine environment needs protection from sediment mobilization ?

Natural sedimentation and siltation are important in the development and maintenance of numerous coastal habitats. Habitats requiring sediment input include coastal wetlands, lagoons, estuaries and mangroves. Reduction in natural rates of sedimentation can compromise the integrity of these habitats, as can excessive sediment loads, which may bury benthic communities and threaten sensitive habitats such as coral reefs, mangroves, seagrass beds, and rocky substrates.

Contaminated sediments, whether they are fresh inputs or dredged, may also lead to pollution, the latter through resuspension or improper disposal.

Anthropogenic modifications to sediment mobilization and sedimentation are made by, inter alia, construction activities, forestry operations, agricultural practices, mining practices, hydrological modifications, dredging activities, and coastal erosion. Effects are generally local in nature, but transboundary implications may occur in some areas where major river systems form a common border and where littoral currents carry inputs across international boundaries.

Research into precise effects of sedimentation from land sources, positive or negative, on productivity and biodiversity in coastal regions has been sparse and more investigation is required to determine:

a) the desired sedimentation rates (quantity) in affected areas;

b) the effects of the various sediment sizes (quality) on affected areas;

c) dating of the sediments to determine the effects of past and present land management practices, and implications for future management (timescales).

2. What is the objective of the GPA in relation to sediment mobilization ?

The objective/proposed target is to reduce, control and prevent the degradation of the marine environment due to changes in coastal erosion and siltation caused by human activities.

3. Which action does the GPA suggest ?

(i) National actions, policies and measures

Actions, policies and measures of States within their capacities should include:

(a) Development and implementation of environmentally sound land-use practices to control sediment discharges to watercourses and estuaries which cause degradation of the marine environment;

(b) Establishment of measures to control, reduce and prevent coastal erosion and siltation due to anthropogenic factors such as land-use, including coastal mining and construction practices, while ensuring that natural erosion supplying sedimentary habitats is not impeded;

(c) Introduction of watershed management and land-use practices to prevent, control and reduce degradation of the marine environment due to anthropogenic changes in sediment loads and contamination of sediments;

(d) Application of practices developed under existing international regulations to prevent marine pollution/degradation from dumping of dredged material and associated dredging operations;

(e) Establishment or improvement of monitoring of sediment transport to the marine environment and associated sedimentation patterns and rates;

(f) Application of environmentally sound management and storage practices for polluted dredged material;

(g) Adoption of measures to minimize changes to natural erosion, sediment transport and sedimentation resulting from the construction of barriers and barrages.

(ii) Regional actions

States within a region should cooperate in the following action:

(a) Promotion of regional cooperation, where appropriate, for the establishment of programmes and priority measures to control anthropogenic modifications to sedimentation/siltation;

(b) Development or enhancement, as appropriate, of regional programmes for the exchange of information on technology and techniques and experience regarding sedimentation/siltation.

(iii)International actions

International actions should include:

(a) Development of methodologies to reduce, control and prevent adverse effects of sedimentation/ siltation, including the formulation of mechanisms for determining changes in sediment mobilization and transport, incorporating relevant quality assurance and standardization procedures;

(b) Participation in a clearing-house for providing information on technologies, measures and experiences regarding sedimentation/siltation;

(c) Cooperation with countries in need of assistance, through financial, scientific and technical support, in the development and implementation of environmentally sound land-use techniques, planning and practices to reduce, control and prevent the negative effects of changes in erosion and siltation rates.