Dredging Intensity: A Spatio-Temporal Indicator for Managing Marine Resources.

Area of Science:

• Marine resource management
• Coastal engineering
• Geographic Information Systems (GIS)

Background:

• Offshore sand extraction is crucial for coastal resilience.
• Assessing the sustainability of sand reserves and dredging impacts is vital.
• Current methods may not fully capture the intensity and location of dredging activities.

Purpose of the Study:

• To present a GIS-based model for assessing offshore sand dredging impacts.
• To utilize vessel monitoring data to quantify dredging intensity and identify extraction zones.
• To provide resource managers with tools to evaluate the sustainability of sand reserves.

Main Methods:

• Employing a GIS model to analyze dredger location, speed, and displacement data.
• Dividing borrow areas into grid cells (e.g., 100x100m) for spatial analysis.
• Generating heat maps to visualize vessel density as a surrogate for dredging intensity.
• Modifying time spent in cells by dredger speed and monitoring vessel displacement to identify active sand removal.

Main Results:

• Heat maps effectively display dredging intensity across designated borrow areas.
• Dredger speed and displacement data allow discrimination between transit and active extraction.
• Identification of specific areas of disturbed benthic habitat is possible, even without bathymetric data.
• The model provides a quantitative assessment of sand reserve exploitation.

Conclusions:

• GIS modeling, incorporating vessel monitoring, offers a robust method for assessing offshore sand dredging sustainability.
• This approach enables resource managers to pinpoint active extraction zones and evaluate potential environmental impacts.
• The methodology aids in understanding the spatial and temporal dynamics of sand exploitation for coastal resilience projects.