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Excavation of 'notches' in foredunes aims to facilitate sand transport through the foredune zone to enhance biodiversity and increase foredune resilience. Recent research has examined notch morphodynamics, however, the underlying aeolian processes in relation to sand transport have not been examined. This study determines:(i) the critical incident wind conditions resulting in sand transport inside the notch; and (ii) the pattern of wind flow and sand deposition/erosion inside the notch.Secondary winds are recorded using 12 ultrasonic anemometers deployed at crossnotch stations and compared with incident winds measured on a mast 6.5 m above foredune crest. Instantaneous sand transport is recorded using 12 laser particle counters located on four masts across the notch. Sand deposition is measured using erosion pins and digital surface models derived from remotely piloted aerial system.Field data are used to validate Computational Fluid Dynamic wind flow simulations to provide three-dimensional wind direction and speed contours in the notch. The study area is

This study examines wind flow dynamics and downwind sand deposition behind engineered notches in a foredune system on a developed coast. Recent studies have examined the morphodynamics downwind of such notches, however, wind flow dynamics and sand deposition in the lee of such notches is not well understood, particularly in relation to artificial foredunes on developed coasts. Wind flow dynamics behind an excavated notch at St Kilda beach, Dunedin, New Zealand is measured using vertical arrays of ultrasonic anemometers. Field data is used to validate computational fluid dynamic flow simulations to examine flow dynamics behind a foredune section with multiple notches. Sand deposition behind the notches is measured using sand pot traps. Wind direction across the depositional lobe aligns with notch orientation and the normalized wind speed increases when the incident wind direction is >10° to the shoreline in a notch that orientates 67° to the shoreline. Wind speed in the swale downwind a notch decreases when the incident wind direction shifts from alongshore to onshore normal. Flow reversal occurs when the incident wind direction approaches onshore normal (>72° to the shoreline). Helicoidal flow appears to occur in the lee of the higher foredune section when the incident wind direction is 74° to the shoreline, while alongshore flow dominates in the lower section. Most sand deposition occurs within 5 m of the depositional lobe of the notch. The orientation of excavated notches should be less than 74° relative to the shoreline to prevent the occurrence of flow reversal in the swale, which might reduce the distance that sand can be transported inland from the notches when the incident wind direction is parallel to the notch axis.

The aim of this chapter is to summarise the main hydrosedimentary processes that take place in estuaries and to present different approaches for their modelling. Section 2 is dedicated to the description of the physical processes involved in estuaries. Section 3 presents the classical (single phase) approach focussing on different ways to model the bed evolutions; the rheological and erosion properties of mud are discussed. Section 4 deals with the two-phase model for sediment transport. Several applications are presented. Finally, the shortcomings of each modelling strategy are discussed and the perspectives are given in section 5