A top-down approach to determine the feasibility and design of a landscaped ecological sand extraction site is made along 3 steps. First, the feasibility of a landscaped ecological sand extraction site is determined using rules-of-thumb. Then a preliminary design of the landscaped ecological sand extraction site is determined using simple tools and parameterizations. The basic design can then be optimized in a detailed assessment using process-based models (3D hydrodynamical models) and species response curves and habitat rules.
Step 1: determine the feasibility of landscaping an ecosystem-based sand extraction site.
- determine the location of the extraction site, the total extractable volume, and existing legislation and potential objections to ecological sand extraction.
- determine the characteristics of the extraction site (sediment characteristics, hydrodynamics, sediment transport, morphology, ecology etc.)
- make designs for a regular sand pit and a design for a deep pit with an extraction depth of about 8 to 30 m and a design for the deep pit with ecosystem-based sand bars.
- determine the life span of the designs, cost for implementing, safety issues and potential for ecosystem-based sand extraction.
Step 2: determine a basic design for landscaping an ecosystem-based sand extraction site
- choose design scenario (to increase biodiversity or biomass etc.).
- determine criteria for evaluation, what result is required to make the project a success?
- determine the most descriptive and influencing abiotic parameter(s) for ecological development. Changing this parameter(s) will determine the chance of successfully creating habitat conditions for the preferred post-dredge situation.
- create and compare histograms of time-averaged bed shear stresses for the traditionally and ecosystem-based landscaped sand extraction site designs using formulae for bed shear stresses under uniform flow. Assuming time-averaged bed shear stresses to be the most descriptive and deterministic abiotic parameter(s) for ecological development.
Step 3: optimize the design for an ecosystem-based landscaped ecological sand extraction site
- set-up and run a process-based hydrodynamic, water quality, sediment transport and morphological models of the regular sand extraction site design and the ecosystem-based sand extraction site, extract year-averaged bed shear stresses, dissolved oxygen levels, organic matter and mud content and seabed morphology.
- determine future ecological response using classification schemes, habitat rules, species response curves or other statistical approaches.
- iteratively optimize the ecosystem-based design based on the design scenario scores.