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To that end, Deltares has teamed up with the offshore industry and certifying bodies to launch a Joint Industry Project: JIP Handbook Scour and cable PROtection (JIP HaSPro). In JIP HaSPro a generic, science-based and systematic comparison is made between different scour protection methods. This comparison is aimed at optimizing existing methods, testing new methods and providing recommendations/guidelines on when and where to apply which method. This comparison is based on an extensive model test programme performed in Deltares' facilities, the scale of which ranges from 1:50 to 1:1, including the world's largest wave flume (Delta Flume), see Figure 1. 

Fig 1: Overview of hydraulic test facilities that were used in the test programmes of JIP HaSPro: (left) Scheldt Flume, (middle) Atlantic Basin; (right) Delta Flume

Scour protection methods

In JIP HaSPRo we focus on three scour protection methods (see Figure 2 for some example). First, conventional (scour protection methods consisting of loose ) rock protection methods are considered against scour for application around monopile foundations or at cable crossing failurescrossings. For these -relatively well understood methods- we aim at filling the gaps of available datasets , by testing a large range of hydrodynamic conditions as well as many different rock gradings. We conduct model tests on different scales to investigate all possible failure mechanisms of the conventional rock protection methods; we . We are focusing on external stability (movement of rock at or away from in the top layer of the scour protection), internal stability (winnowing of underlying sand through the scour protection layer) as well as flexibility in case of edge scour or a lowering ambient seabed (falling apron behavior) of loose rock scour protectionsbehaviour). Based on the extensive dataset, new scour protection design formulae can be developed.

Additionally, within the JIP HaSPro we test and assess many innovative protection methods in experimental conditions, some of them for the first time, to provide us with alternative solutions to help reduce the costs by simplifying the installation phase, facilitate monopile easier decommissioning and finally protect against scour , around infrastructure that is situated in highly dynamic environments where extreme morphological changes and hydrodynamic conditions are expected. Examples of such innovative scour protection methods are concrete block mattresses, gabions, artificial vegetation, ballast-filled mattresses and self-installable systems.

Lastly, we focus on eco-friendly scour protection methods. Nature-inclusive design of scour protections is aimed at increasing the potential ecological value that of wind farms add to marine environment, by providing shelter for target species such as Atlantic cod or by contributing to restoration of previously booming abundant oyster reefs that degraded due to human pressure and diseases, like the former Oyster Grounds in the North Sea. In Besides,in JIP HaSPro we build construct an ecological framework that accounts for the existing legislation and guidelines and provides a consolidated basis for the offshore wind industry to make choices concerning all phases of nature-inclusive design (design, construction & operation and decommissioning). Furthermore, we test the hydraulic stability and overall performance of scour protections that include ecological elements like various types of shells and constructive elements such as (modified) reefballs and pipes.

 

Fig 2: Examples of test set-ups of several considered scour protection methods: (from left to right) 1. selfinstallable scour protection based on artificial seaweed; 2. testing deformation of scour protections situated on top of sand wave crests; 3. eco-friendly rock berms aiming at restoration of oyster reefs; 4. 3D-measurement of rock protection in Delta Flume test, considering winnowing for two different rock gradings; 5. eco-friendly scour protection design

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