Beach-dune modelling in support 241 of Building with Nature for an integrated spatial design of urbanized sandy shores

Kathelijne Wijnberg1, Daan Poppema1, Jan Mulder1, Janneke van Bergen2, Geert Campmans1, Filipe Galiforni-Silva1, Suzanne Hulscher1, & Paran Pourteimouri1

1. University of Twente, Water Engineering and Management 2. Delft University of Technology, Faculty of Architecture and the Built Environment

DOI 10.47982/rius.7.136 KEYWORDS sediment nature, wind-driven with building design, shore, coastal spatial urbanized modelling, beach-dune dynamics Abstract critically of sandy shores existence physical on a depends The long-term it Nature with Building principles of the From budget. sediment balanced some should employ shores sandy of protection sustainable a follows that of urbanized sandy design process In the spatial nourishment. form of shore and knowledge the be integrated, must functions multiple where shores, play thus morphology beach-dune and dynamics sediment of prediction the who scientists coastal with typically resides expertise This role. essential an models morphological of types various in knowledge their condensed have that serve different purposes and rely on different assumptions, thus have their specific strengths and limitations. This paper identifies morphological shores sandy urbanized of design spatial integrated the for needs information using BwN principles, outlines capabilities of different types of morphological models to support this and identifies current gaps between the two. A clear human of buildings and accompanying absence the from arises mismatch developments morphological simulating models numerical current in activities in beach-dune environments.

RIUS 7: BUILDING WITH NATURE PERSPECTIVES 242 BEACH-DUNE MODELLING IN SUPPORT OF BUILDING WITH NATURE FOR AN INTEGRATED SPATIAL DESIGN OF URBANIZED SANDY SHORES 243 - - (BwN) for sandy shores: for sandy (BwN) Building with Nature ecosystem services. Therefore, a services. Therefore, truly integrated spatial ecosystem Coastal dunes on sandy shores provide provide Coastal shores multiple on sandy dunes ecosystem services to - shores, the prime support like the case of dynamic landscapes In sandy - Solutions for coastal protection are needed most where shores are ur The essential role of sediment dynamics in BwN design - makes morpho Introduction 1. urbanized urbanized coastal areas: they protect against flooding by offering to live and a higher ground against regulating on (a storms ser ecosystem a buffer spatial ar- combines functions into a favourable all desired design not only supporting the also explicitly use rangement, it must and take into account ecosystem services. physical existence sediment cycle. The long-term service is the ing ecosystem critically depends on a balanced sediment budget, which is shores of sandy -dynam budgets and sediment to sea level rise. Therefore, connected closely vice), provide drinking water by collecting and filtering water in the coastal environment an attractive provide and (production service) lens freshwater an service). A good spatial design for (cultural beach tourism and leisure for into spectrum of these functions takes the full area beach-dune urbanized account. However, services these desired ecosystem exist can only by the grace of the supporting shores. sandy spatial ics sustainable are essential in any design of urbanized This leads to our definition of to redistrib- morphodynamics tides, wind) and (waves, forces using natural to achieve locations in order integrated spatial to desired design ute sediment goals. coastal landscapes following banized. Developing such solutions in urbanized BwN principles requires an integrated spatial design, intro- which not only duces additional, possibly contrasting, and but also adds functional demands, the new challenge of how different functions will interact morphologically. shores, the built encroaches onto the beach environment urbanized On many of the dune, in front or series of beach huts of beach restaurants form in the such as board walks and concrete pathways (fig- and related infrastructure ). ure.1 Such structures interact with wind-driven flows of sediment that are Therefore, making an to protect the shore. part of BwN solutions an inherent integrated spatial design to solve these conflicts – or moreof demands likely functional both of prioritize knowledge requires – accordingly optimize and the services and of morphological interactions between them. logic a crucial The challenge for spa- part of the design process. modelling tial designers is to develop spatial designs in a beach-dune environment that must remain dynamic because of its BwN functionality. - Zandmotor, 2017) mega-nourishment, The Netherlands. (Source: This implies they not only need to understand how static structures in- static how This implies structures only need to understand not they been developed by coast- coastal morphological have models Numerous the considered specifically never have far so modelers knowledge, our To Example of urbanized shore with ‘Building with Nature’ intervention; Kijkduin, Sand Motor Figure 1. Example of urbanized shore with ‘Building with teract with the wind-driven sediment flow but, as part of the spatial design process, to actively use such interactions. This way a true BwN de- also need become location of structures and sign solution is achieved where presence do so, morphological To shores. spatial part of a dynamic for urbanized design designs spatial possible different of impact the evaluate to needed are models and design principles. (See Van Bergen et al., 2020, for actual examples of such design principles). However, it is often for various purposes. al scientists and coastal engineers unclear for spatial designers what can be expected these models with from temporal and spatial respect of the simulation, to level of detail accuracy, de- models Furthermore, are suitable. scales of problems for which models than others because develop modelers scribe certain aspects more accurately in mind. their models with a certain purpose of spatialinformation needs designers when developing beach-dune models. Therefore, this paper identifies morphological information requirements in using BwN principles. shores sandy the spatial design process of urbanized It also outlines the capabilities and limitations of different types of morpho- logical to simulate impacts models constructions on beach-dune devel- of bridge the ‘language gap’ between spatial mor designers and opment. To

RIUS 7: BUILDING WITH NATURE PERSPECTIVES 244 BEACH-DUNE MODELLING IN SUPPORT OF BUILDING WITH NATURE FOR AN INTEGRATED SPATIAL DESIGN OF URBANIZED SANDY SHORES 245 - - - - pro- 1 context. That is not just spa- is not dynamic context. That ’ phase of the design process, design re- ’ phase of the In the ‘inquiry and analysis In landscape understanding The above type of information is important for An integrated spatial design of urbanized sandy shores requires under shores sandy of urbanized integrated spatial design An Morphological information needs for integrated spatial information needs for integrated Morphological shores design of urbanized ShoreScape is a research project that aims to develop knowledge, tools and design principles for the principles tools and design knowledge, ShoreScape is a research project that aims to develop sustainable co-evolution of the natural and built environment along sandy shores. standing and prediction of sediment dynamics and morphological and change in prediction dynamics standing and of sediment (Van Bergen et al, built environment (possibly) dynamic interaction with a 2020). The specific morphological information needs vary during the differ- outlined below. ent phases of the design process, as quirements and context are explored to grasp parameters of the urban the and eco-morphological involved. In the case of a BwN ap spatial systems on the proach, this requires information at a given time, in a tial characteristics of the system as can be represented behaviour. system’s Geographical (GIS), but of the full System Information For instance, considering a specific scheme, nourishment which beach width variation over time, or which combinations of dune height and width can be are char- design? What waterfront expected a planned of areas to develop in acteristic bed level profiles across the beach-dune zone during this develop- exist mechanisms to direct the location ment? Which morphodynamic and of erosion and deposition amount using buildings placed at the beach (such as already present on Fig. 1 in for recreational use)? Additionally, this phase of the design rules of thumb are desired that summarize interactions process of buildings with wind-driven sediment flows. For instance, a simple formu of amount spacing relation between inter-building the la describing the and blockage of wind-driven sediment flow. Similarly, what would be the sed iment blockage of their vertical dis- factor of raised buildings as a function tance above the beach? for the exploration parameters processes and to identify of possi- and urban with wide shores beach- spatial Integrated designs for urbanized ble futures. as at large spatial variations therein, such and es, rapidly eroding shorelines ject. Hereby, we aim to match the morphological information requirements of morphological requirements the information we aim to match ject. Hereby, spatial designers and morphological model capabilities to knowledge identify needs for integrated match information do not models gaps current where shores. of urbanized spatial design 1 2. phological modelers, we have attempted to avoid jargon, or explain or jargon, it, and avoid to attempted phological we have modelers, illustrate different approachesthrough examples from the ShoreScape - - ’, different spatial arrange- spatial different ’, ’, between dif- interactions Finally, in the phase of ‘design optimization design feasibility phase of ‘design subsequent the In In the context of simulating topographic changes (related to sand trans context of simulating topographic the to sand changes (related In Model types for evaluating morphodynamics of the beach- Model types for evaluating morphodynamics shores dune system on urbanized sandy ferent design aspects are studied in detail and optimized. Now decisions have ferent design aspects are studied in detail optimized. and Now decisions have to be made that have financial consequences and thus requirea higher level and precision of morphological information. For example, of accuracy when scheme and arrangement considering sea level rise, a proposed nourishment flood that such dunes, the of growth natural guarantee should houses beach of This will be maintained. dunes by the values provided natural levels and safety in requires detailed information about, of sand amongst others, the amount over time, including a prediction dunes of its topographicthe evolution, to enable the application of models that test flood safety levels through time. solution, by underpinned This optimization process will lead to a favourable of morphological modelling. quantitative tests based on the output ments are tested and combined into one design. Interactions of urban design tested and combined ments are into of urban design. Interactions one and morphological ‘rapid by so called are studied development prototyping’. For example, when planning for beach housing in a formation zone, dune var- ious layouts are explored by systematically varying the types and - configura tions of buildings and the timing of their placement. A combination of several design aspects will lead to variants and plausible solutions, ready to fit the program. urban dynamic context and port by wind and water) in a beach-dune environment, the term ‘model’ or ‘morphodynamic model’ refers to a simplified version of reality that, in its very essence, incorporates topography (bed elevation) and the sediment transport processes that change it. Models differ intypes of mod we can identify three processes. Broadly, transport sediment how they incorporate els, differing in their simplification approach: conceptual models, physical For a lab experiments), numerical simulation models. ((scaled) and models can be split environment, numerical simulation models into pro- beach dune the following, In we models. behavioural rule-based and cess-scale models will explain these different modellingapproaches, what type of information they can provide as well as their present, or inherent, limitations. 3. ), will most likely differ from those with more gradual more with those from differ likely most will 1), (figure Motor the Sand fronts. dune advancing seaward and slowly positions shoreline advancing

RIUS 7: BUILDING WITH NATURE PERSPECTIVES 246 BEACH-DUNE MODELLING IN SUPPORT OF BUILDING WITH NATURE FOR AN INTEGRATED SPATIAL DESIGN OF URBANIZED SANDY SHORES 247

2 ). figure.2 given coastline (modified after Psuty, 2004). Rules of thumb also are conceptual models and have a quantitative - ele have and also are conceptual models of thumb Rules Conceptual models Conceptual a conceptual modelling, of morphodynamic context the refers model In A sand-drift dike (stuifdijk) is an artificially created linear dune ridge, initiated by erecting long lines of plant- by accompanied often sand, windblown capture to sandflats coastal on willow and bundles reed ing marram grass at a later stage. Traditional Dutch coastal maintenance practice (see Boeschoten, 1954). storage in the foredune (max. foredune dimension) and maximum inland sand transport expressed storage in the foredune (max. foredune dimension) system. Note that for the situation of a slightly negative sediment budget of the beach, maximum sand system. Note that for the situation of a slightly negative Example of a conceptual model, showing the relationship between the sediment budget of the Figure 2. Example of a conceptual model, showing the relationship beach and the resulting sediment budget of the foredune with related topographies of this sand-sharing beach and the resulting sediment budget of the through parabolic dune development, are closely positioned and may even occur simultaneously along a through parabolic dune development, are closely 2 ment to them. For example, to them. in a given ment region, dikes initiation of sand-drift to a schematization of the beach dune systems in a qualitative in a qualitative - It de to a schematization manner. systems beach dune of the scribes, in words, how beach-dune topography changes under the influence often with surplus), or sediment as wind, more factors (such of one or waves, between sketches. Relations of diagrams and the help bed level factors and in are often described changes of positive terms or negative Con- feedback. based on a combination can be ceptual of phenomenological knowl- models edge, derived from field observations, and theory (first analogies). For example, how various dune typologies (2004) describes Psuty principle physics, with a diagram of links these eroding beaches and develop on accreting and for beach and foredune ( curves sediment budget - - - - archetypical situations and underlying principles (e.g. Fackrell The reduced complexity scale of physical models, in comparison to The reduced and A conceptual model generally forms the basis for developing the basis numerical forms a generally A conceptual model Physical models – scaled lab experiments Physical models – scaled lab experiments system, sim- A physical model is a tangible representation of a natural used to examine hydro are mostly coastal studies, physical models In Investigate (1984) and Martinuzzi and Tropea (1993) on the flow structure around a rules of thumb for indicating types of natural topographic evolution to be indicating for types of natural of thumb rules beach dune system. expected in different zones of the a fast overview of possible, first order impacts on morphology of- interven tions/designs or objects

- dynamics and morphodynamics and are generally developed dynamics and morphodynamics in a laboratory basin to storm study setting. For instance, Boers et al. (2009) used a wave over or buildings around flow wind system; dike-and-dune scaled a of erosion (e.g. Fackrell, Wiggs 1984; 1996). et al., in wind tunnels can be studied dunes Occasionally, physical experiments are located in a field setting. For exam- ple, dike a full-scale breach experiment al. (1991) conducted Visser et Het at of effects examining beach the at experiments scale are examples Other Zwin. building patterns in geometry on sedimentation and erosion their surround ings (Poppema et al, 2019). the full-scale, real world setting, makes them flexible, relatively cheap and easy to adapt, and suitable to: - - will be unsuccessful when the sandflat is less than 1.3 m above mean sea level sea mean above m 1.3 than less is sandflat the when unsuccessful be will on empirical often based are of thumb 1954). Rules (Boeschoten, that relations may be derived from field monitoring or lab experiments (physical models), they may as well although form a of schematizing way derived from insights as process-scale derived, as well Empirically models. simulation numerical morphody input for rule-based can form of thumb rules modelling-derived models. namic simulation simulation model by providing the elements that may be quantified in nu merical Conceptual simulation models. morphological do models themselves not provide quantitative change, information on rates of volumes, sediment or specificcomplications that could arise from interventions. Morphological provide: morphological models to experts may use conceptual plified, but still faithfully reflecting important relationships between rele- can be in a physical model measurements and vant processes. Observations As itself. system natural of the about the behaviour to infer information used temporal scale, they spatial and built on a reduced are often physical models are also called scale models.

RIUS 7: BUILDING WITH NATURE PERSPECTIVES 248 BEACH-DUNE MODELLING IN SUPPORT OF BUILDING WITH NATURE FOR AN INTEGRATED SPATIAL DESIGN OF URBANIZED SANDY SHORES 249 - - - (e.g. ‘can a funnel-shaped configuration configuration funnel-shaped a ‘can (e.g. (e.g. ‘Does beach house configuration X lead to to investigate its effects (e.g. gradually gradually (e.g. effects its investigate to variable specific a vary design performance explorative explorative design questions Fig. 3) in order to derive general rules for the effects of building- dimen Physical models also have drawbacks and limitations. As for all types of limitations. As for all types drawbacks and also have models Physical An example application of physical models in the context of urbanized An example application in the context of urbanized of physical models the desired sedimentation pattern?‘). the desired sedimentation of a series locally in- the dunes, induce located seaward of of beach huts, of a series the dunes?’); supply towards creased sediment Evaluate increasing wind speed to examine deposition patterns around houses like houses around patterns to examine deposition speed wind increasing accumulation); (2018) did for snow Liu et al. Answer cube); Systematically

- models, processes not included in the model can be an issue (e.g. growing vegetation). On top of this, a basic models is problem of physical scaling. If in a wind of a beach house scale model (e.g. using a 1:20 the geometry is scaled experiment), regard representation of real world conditions tunnel a faithful ing wind and sediment requires other properties as weights, ing requires other (such and sediment wind ve- forces, locities, and time scale) to be scaled as well. This scaling physical involves scaling laws that may pose conflicting constraints on how scaling should oc- As a result, scaling cannot be perfect, and the model maker has to decide cur. properly. which processes are chosen and scaled beach modelling, is to examine effects of building size and shape on size and location of deposition and erosion patterns. In the ShoreScape project, we beach the on dimensions of buildings with various placed cuboid scale models (see morphological sions that can be used in rule-based (see computer models of in a wind on the beach instead We placed scale models the section 14.3.4). scaling to reduce some of the issues and remove limitations tunnel of the physical size of a By using wind scale tunnel. models, instead of full-scale ob- jects, one can more easily vary test configurations. Other advantages of field deployment are that longer-term effects with changing wind conditions can variations transport wind and sand natural be examined and that inherent brings a clear disadvantage This simultaneously are automatically captured. of field deployment: one cannot control weather conditions, hence experi conditions, wind different experience will days different on performed ments complicating a comparison of results on different days and requiring care- The latter can be supported by developing ful interpretation. complementary the experimentsusing CFD where modelling (see Section 14.3.3) numerical influence of different wind speeds can be systematically studied and under stood. ------increasing scale model width. Process-scale numerical simulation models using CFD Process-scale numerical Computational (CFD) enabling computers to Fluid Dynamics is a method Sediment transport depends on flow conditions, so CFD can be used to By limitations. also but advantages has problems flow solve to CFD Using An elevation map (left) and orthophoto (right), showing the erosion and deposition around orthophoto (right), showing the erosion and Figure 3. An elevation map (left) and the same set-up with two scale models of buildings that differ in width. As an example, the measured scale models of buildings that differ in width. the same set-up with two dimensions indicate that both the width and length of the deposition upwind of the models increase with both the width and length of the deposition upwind dimensions indicate that solve problems of flow in liquids as well as gasses. In fluid dynamics, flow is physical laws, include continuity of mass, which described by fundamental and energy. These laws describe how these quantities momentum change in time and space due to physical processes. This means that flow properties these are described through and temperature like density, velocity, pressure practice, equations. In equations are not easy to solve. Numeri the model cal techniques can be used to find approximate solutions for these equations, these for solutions approximate find to used be can techniques cal the Therefore, directly. be solved equations cannot as the continuous model equations a set of algebraic model are discretized into equations. This can be achieved by subdividing the computational domain into a finite number of small cells. These discrete equations can then be solved to find approximate solutions of flow properties. flu the in variations Spatial models. transport sediment of forcing the obtain id flow near the sand surface result in spatially variable sediment transport erosion at one location, through rates, which causes bed level changes and flow the affect again changes level bed these return, In another. at deposition field, closing the feedback loop, also known as a morphological loop. increasing the number of cells, solution converges the numerical toward the find for powerful very be can method solution this Therefore, solution. exact increasing However, space. and time in resolution high in properties flow ing of the number cells also increases the computational time required. There a balance between computational fore, in CFD is always simulations, there variables all where experiments, field with comparison In resolution. and cost

RIUS 7: BUILDING WITH NATURE PERSPECTIVES 250 BEACH-DUNE MODELLING IN SUPPORT OF BUILDING WITH NATURE FOR AN INTEGRATED SPATIAL DESIGN OF URBANIZED SANDY SHORES 251 - turning processes on turning through CFD, which can result in rules of thumb. through CFD, which can result in rules vary the value of a specific variable to investigate its effects. detailed flow and sediment transport estimates around a single design in simulations. Processes that could be investigated are for instance: that could be Processes in simulations. This makes CFD models suitable to: CFD models suitable This makes - Even though computers become increasingly powerful, solving turbu A preliminary result of the use of CFD ShoreScape of the modelling in the project result A preliminary Systematically Parameter values can be precisely specified, or certain processesincreasing gradually on processes of interest. (e.g. eliminated to focus can be patterns deposition and erosion of size on influence examine to speed wind around houses) Focus on specific aspects of the problem of interest by and off and affect wind driven sediment transport. does soil moisture Compute for very short timescales (up for very short minutes) and a limited to number of condi- tions. Solving airflow equations around buildings requires solutions for a wide range of spatial scales; from the large-scale flow around the building to small-scale flow structures in the turbulent wake behind the building. Even though the small-scale flow structures will wide range of spatial scales limits time the simulated to several minutes. be parameterized, the or days. hours Computational times typically take Obtain system knowledge

- are constantly changing, changing, CFD are constantly investigation a systematic allow simulations of the impact of specific variables of interest. Numerical modelling tool for providing powerful insight into are processes. Model physical results can be a often simplifications of reality and thereforewill not replace experimental to experiments. but rather be complementary research, - - - lent wind flow at the required level of detail and fast enough for a long-term is not yet realistic. Average morphological evolution of quantitative accuracy, flow simulations can be used but result in a lack of physics on smaller scales. Note that most morphological models used in coastal engineering applica tions are hydro-morphodynamic models that use a more schematized way of tions are hydro-morphodynamic CFD modelling, of meters and often only with cell sizeshundreds of tens to depth-averaged fluid flow instead of the full 3D flow field. These models can be applied seabed to simulate the development of the submerged nearshore evolution and can be shoreline used, for instance, to evaluate the longer-term and currents. due to waves of mega-nourishments in Fig. 4. is shown CFD can provide detailed airflow patterns around various transport Aeolian sediment of beach houses. arrangements geometries and are de- equations that transport be computed by using sediment can then calculated are which velocities, flow bed near and stress shear bed on pendent The morpholog- CFD computational domain of the each cell in the model. for - - within the cell (which would to red colours indicate low to high flow velocities. to red colours indicate low Rule-based coastal morphodynamic models Rule-based coastal morphodynamic Like describe models the CFD morphodynamic models, rule-based The evolution of the beach-dune topography The evolution of the beach-dune is calculated by applying Example snapshot of calculated flow field around a cube-shaped building using CFD modelling: flow field around a cube-shaped building Figure 4. Example snapshot of calculated a) side view, slice along centre line z/L=0, b) top view, slice along y/L=0.5. Fluid flow from left to right. Blue line z/L=0, b) top view, slice along y/L=0.5. a) side view, slice along centre ic change is the from derived can Simulations sediment. of conservation be model the physical scale of at the but also houses, scale beach for full made beach by Poppema interpretation (2019) to support et al at the experiments patterns in sedimentation of observed mechanisms and underlying terms of scaling effects. test for possible ally a two-dimensional surface. The difference lies in the rules that describe the state of each represent cells. Discrete numbers of these the behaviour type of vegetationcell, depth of and in the grid cell (e.g. its elevation, density define that rules transition to according change can states Cell groundwater). on the previous state of a cell depends state of this cell and how the current For example, probability cells. deposition the of sediment of its surrounding in presence of vegetation a cell depends on the beach-dune topography using a large cells on a number of regular grid, usu trap the presence of a sediment) and on higher elevation in an upwind cell (a dune creates a shadow zone with decelerated wind and increased deposition governed cell states discrete and with grid cells behind it). This type of model, (CA) to as Cellular Automata referred by transition rules, is most commonly model (Fonstad, 2013). each iteration multiple times to all grid cells, where transition rules these (i.e. application rules to of the all grid cells in the model) represents a time that control cell state transitions can be step. The mathematical as functions create a simple, or complicated, as desired to achieve the aim of the model. To system, a physical rationale for the math meaningful CA model of a natural ematical functions of each transition rule is essential. Transitions should be be should ematical functions of each transition rule is essential. Transitions based on general rules or on empirical estimates derived from measurements and must account processes required for all necessary the desired pattern/ for phenomena.

RIUS 7: BUILDING WITH NATURE PERSPECTIVES 252 BEACH-DUNE MODELLING IN SUPPORT OF BUILDING WITH NATURE FOR AN INTEGRATED SPATIAL DESIGN OF URBANIZED SANDY SHORES 253 - - - - (e.g. can dune (e.g. ‘can strategic, through space (e.g. the (‘How present houses in do seasonally process interactions So far, the DUBEVEG (Dune, Beach and VEGetation) model (Keijsers et al., et model (Keijsers and VEGetation) Beach (Dune, So far, the DUBEVEG The main advantages of CA modelling are its flexibility and range of A limitation aeolian sediment total is that of the beach-dune CA model Following from all advantages and limitations, CA for beach- models Investigating underlying principles Investigating underlying of archetypical situations formation be explained solely from shadow zone effects andavalanching when slopes become too steep?). Investigating front of a dune affect this dune?’) ‘Rapid prototyping’ to answer explorative design questions time-varying placement of beach houses help build up a dune?’) Qualitatively comparing designs (‘will a design with larger distances between houses result in a higher dune? ‘)

2016, 2016, Galiforni-Silva et al., 2018, is 2019) attempt the only beach- to simulate solely using dune development a CA approach. includes the main It - process es involved in such as wind-driven beach-dune system, dynamics of the the erosion and transport, vegetation sediment decay, hydrodynamic growth and supply, depth. Model groundwater and applied rules are with a weekly time wind-driven sand step, of a given the assumption under long-term average transport. This results in computing short times, making suitable the model studies over tens of years. for long-term morphodynamic modelling possibilities with a relatively low computational effort. Rules can needs only For instance, DUBEVEG easily adaptable. be simpleare usually and sediment transport rules without separate rules for fluid flow (air or water), essen an are computations flow fluid repeated where models CFD to contrary - - - - tial and computationally intensive component. tial and computationally long-term from or models other from derived either user-specified, is supply volume sediment total wind-driven monitoring data. This implies the that increase, over totalled the simulated period, is imposed by the user and not an outcome of the interacting processes in the model. Also, because CA mod transport changes in sand els focus on interactions at a certain location (e.g. a of objects than the movement around dune), rather required as fluxes sand simulate not does model the grains), sand of transport (e.g. comparison to a measured validation methods model used commonly for sand flux). CA model outcomes can therefore only be validatedlevel of aggregation, and spatial such as overall trends patterns in morpholo at a higher predic quantitatively accurate as a used gy. Hence model outcomes cannot be topography at a given time. tion or reproduction of beach-dune than predictive exploratory rather as useful are currently dune dynamics suitable for: tools. Their characteristics make them sedimentation/erosion on sedimentation/erosion . Here, . Here, Fig. 5 a of beach series houses specific rules for the impact of rectangular objects rectangular of impact the for rules specific - A BwN approach for developing integrated spatial designs for urban An example An example output of the of a CA simulating model impact the of beach Matching morphological information needs and Matching morphological information morphological model capabilities solid), transects without beach houses (black solid, where green infill indicates sedimentation). solid), transects without beach houses (black solid, it should be noted that the CA model used does not yet include rules that specify the impact of bluff- it should be noted that the CA model used does transects crossing the middle of a beach house (red dashed), transects in between beach houses (red transects crossing the middle of a beach house topography after 10 years simulation, white rectangles represent beach houses; b) top view of beach- topography after 10 years simulation, white rectangles Example illustrating a possible outcome of implementing beach houses in a CA model, where Figure 5. Example illustrating a possible outcome of implementing body objects, such as beach houses, on local sedimentation-erosion patterns. a) Top view of beach-dune body objects, such as beach houses, on local sedimentation-erosion dune topography at start of simulation, rectangles represent beach houses; c) average topography along dune topography at start of simulation, rectangles 4. ized sandy shores requires morphological and large shores ized modelling at both small sandy coastline larger scale evolution of the to predict the requires models It scales. under different nourishment strategies as wellas the evolving topography of term scales. For shorter on smaller beach the latter, and dunes understanding houses on dune is development on dune in shown houses are implemented in the CA model DUBEVEG by defining non-erodible cells and adding a that states a rule zero probability for sand deposition on top of a a 4 are 2.5 m high, The nine house. houses 4 m wide, and 10 m long, have and m spacing. As we in version described used the DUBEVEG Galiforni-Silva et al (2018), patterns have not yet been implemented. patterns have not yet

RIUS 7: BUILDING WITH NATURE PERSPECTIVES 254 BEACH-DUNE MODELLING IN SUPPORT OF BUILDING WITH NATURE FOR AN INTEGRATED SPATIAL DESIGN OF URBANIZED SANDY SHORES 255 ------In the In the phase of ‘design feasibility’, it is ‘rapid prototyping’ that puts high In the ‘inquiry and analysis’ phase of spatial design, conceptual mod phase of spatial analysis’ and ‘inquiry the In els, physical scale models, and CFD els, physical scale to meeting identi- all contribute models fied morphological information needs. In this context, CFD modelling serves two main purposes. Firstly, detailed 3D airflowsimulations combined with mech- insight into underlying enhance calculations may transport sediment anisms of building impacts patterns, leading on erosion/sedimentation to to hun (grid size of tens CFD grid coarse models Secondly, of thumb. rules dreds of meters) with highly reduced complexity fluid flow equations orsur- rogate modelling techniques (e.g. et Berends al., 2019), can be used to pro- vide morphological information on the approximate effects of nourishment schemes on the coastal profile or shoreline position over many years to a few Regarding decades. wind-driven sedimentation and erosion modelling of around buildings, many studies exist that model airflowtrans sediment calculated related have et al., 2016), but none (e.g. Ozmen around buildings A few modelling studies exist port patterns. where zones of acceleration and building, induced by the were surface, deceleration of the wind near the sand deposition interpreted as zones of erosion and 2018). Note (e.g. Van Onselen, current-driven and modelling of wave- numerical process-scalethe that - at ur coastal protection structures hard erosion around and sedimentation (e.g. Smallegan et more advanced banized is much such as seawalls, shores, al., 2016; Muller et al, 2018) computational time of long-term morphological on the simulations demands (covering several years to It requires tens of years). models that numerical can quickly evaluate morphological effects of multiple spatial design alter natives, considering the interaction of buildings and sediment flows, as well as interaction with vegetation development (all of which influence dune for the most suitable type of model, mation). This makes CA models currently interactions of buildings with for include rules yet do not they even though Also, it has been observed that activities transport. wind-driven sand related to the recreational use of the beach, such as me- local beach does as development, dune raking hence and growth vegetation or affect may beach traffic, and deposits by property owners (Jackson chanical removal of aeolian sand beach-dune Respective2011). relations are still lacking in current Nordstrom, morphological models. interactions of wind-driven sediment transport, vegetation transport, sediment wind-driven of interactions - de dune growth, velopment, built and the use human to are essential environment simulate consequences the long-term upper for the beach evolution. Under dune and standing and modelling these complex and modelling these standing interactions, has to where sediment move the domain submerged from to the subaerial and interact domain there with the biotic socio-economic and the system is of at the frontiers system et al, 2016). (Lazarus coastal modelling - - - - principles spatial of urban in the design Using ‘Building with Nature’ predict the mor able to accurately (computer models) Numerical models Regarding Regarding optimization’, of ‘design the phase morphological expressed Conclusion phological effects of interaction between wind-driven sediment dynamics lacking. severely felt in the phases This is most buildingsand are currently of ‘design feasibility’ and ‘design optimization’, where alternatives like - con analysis’ and ‘inquiry the in useful particularly – models physical and ceptual phase – are less suitable. In the ‘design optimization’ phase, a gap exists be- tween model capabilities and morphological information needs as it is diffi- with nu supply to dunes sediment long-term predict the cult to accurately merical models. Finally, the observed influence of human activities on urban absent in all morphological beaches on vegetation development is currently will be formation rate of new dune Hence predicted location and/or models. beaches. for urbanized inaccurate 5. ized sandy shores asks for a new design approach. A recognition inter- asks for of the shores ized sandy implies the spatial systems morphological and between urban connectedness and adaptive,need for dynamic instead of static, Combining designs. the de- econ- and recreation nature, protection, flood – multi-functionality for mand omy – while at the same time explicitly considering and utilizing sediment dynamics, requires integrated truly spatial design. This poses new challenges it. to morphological models supporting information requirements seem to be seem requirements information static of in the tradition rooted spatial in However, precise. and detailed highly be can design final the where designs, situation static a not is design final the designs, spatial BwN-based of case the evolving dynamic, situation but an inherently and a static situation end will future of functionality defence flood of assessment the Regarding exist. never 2018). (cf. Vuik et al, landscapes, adaptive be needed approaches may dune objects in with hard level of a dune safety of the Moreover, the assessment or on top of it, is still a difficult issue (e.g. Boers et al., 2009). Apart from the difficulties ofknowing details of future beach-dune topography, even pre- challenge. No area is still a major in a dune dicting of sand the total amount prediction supply of long-term sediment yet for accurate are available models in domains subaerial and subaqueous coupling in efforts Recent dunes. the to Roelvink studies (e.g. numerical model and Costas, 2019; Hallin, 2019) help to obtain quantitative is supply that in the time-varying amount of sand insight and can be and tides picked up by wind for continued delivered by the waves capabilities In short, present-day transport. onshore of morphological mod are still limited. els to support design optimization

RIUS 7: BUILDING WITH NATURE PERSPECTIVES 256 BEACH-DUNE MODELLING IN SUPPORT OF BUILDING WITH NATURE FOR AN INTEGRATED SPATIAL DESIGN OF URBANIZED SANDY SHORES 257 - To arriving conclude, spatial integrated at sustainable for the designs To Acknowledgements This paper been has written in of the ShoreScape the framework project protection of urbanized sandy shores using BwN principles principles BwN using shores - morpho requires sandy protection of urbanized of simulation hydro-morphological the can go beyond that logical models with how humans interactions can include alone and behaviour nourishment use the beach. and built environment along sandy (Sustainable co-evolution of the natural shores), funded by the Netherlands by Hoogheemraad number ALWTW.2016.036, co-funded (NWO), contract Organization for Scientific Research schap Hollands Noorderkwartier and Rijkswaterstaat, and and in kind supported Noorderkwartier schap Hollands Architects. and H+N+S Landscape by Deltares, Witteveen&Bos, - (6), 121 (1), 85–92. (1), 115 Journal of Wind Journal of (7), 885–897. 885–897. 68(7), , 810-823. doi: , 810-823. Treatise on Geomor- , 58–69. https://doi. 58–69. , Journal of Wind Engi- , 103520. https://doi. , 103520. 329 152 , Ocean Dynamics, Journal of Fluids Engineering, Journal of Coastal Engineering Proceedings Coastal Sedimentsof 2011 (1), 97–118. https://doi.org/10.1016/0167-6105(84)90051-5 The , 1–13. https://doi.org/10.1016/j.jweia.2017.12.010 , 16 , 81–90. https://doi.org/10.1016/j.geomorph.2015.07.043 , 3(2), 181–196. https://doi.org/10.1016/j.aeolia.2011.03.011 , 173 (No. 330267). Ministerie van Ver- Ministerie Stuifdijken op Terschelling en Vlieland (No. 330267). Long-term beach and dune evolution: Development Long-term beach and dune evolution: Development and application of the CS-model (Doctor- References org/10.1016/j.coastaleng.2019.103520 sion. In: M. Mizuguchi & S.Sato (Eds.), 10.1142/9789814355537_0061 keer en Waterstaat, Rijkswaterstaat, Directie Friesland (RWS, FR). https://puc.overheid.nl/rijkswater - staat/doc/PUC_122849_31/1/ Aerodynamics Engineering and Industrial org/10.1016/j.geomorph.2018.12.012 1161–1181. https://doi.org/10.1002/2015jf003815 coastal systems. Geomorphology, 256 neering and Industrial Aerodynamics Fully Developed Channel Flow (Data Bank Contribution). https://doi.org/10.1115/1.2910118 Towards efficient uncertainty quantification high-resolution with morphodynamic models: A multi- fidelity approach applied to channel sedimentation. in response to climate change. Journal of Geophysical Research:coastal dunes Earth Surface, building models based on open air snow-wind combined experimental facility. phology (pp. 117–134). Academic Press. https://doi.org/10.1016/B978-0-12-374739-6.00035-X scales. Geomorphology, decadal at development dune coastal on variability inlets. to close flats sand at development dune coastal on depth water https://doi.org/10.1007/s10236-018-1162-8 al dissertation, Lund University). https://lup.lub.lu.se/search/publication/e850cf42-d671-4790-ab62- 7c43830e7f6a systems: A review. Aeolian Research Fonstad, M. A. (2013). 2.9 Cellular Automata in Geomorphology. In J. F. Shroder (Ed.), Shroder F. J. In Geomorphology. in Automata Cellular 2.9 (2013). A. M. Fonstad, Boers, M., Van Geer, P., & Van Gent, M. (2011). Dike and dune revetment impact on dune - ero Boeschoten, J. C. (1961, January). Fackrell, J. E. (1984). Parameters characterising dispersion in the near wake of buildings. Galiforni-Silva, F., Wijnberg, K. M., de Groot, A. V., & Hulscher, S. J. M. H. (2018). The influence of ground Lazarus, E. D., Ellis, M. A., Brad Murray, A., & Hall, D. M. (2016). An evolving research agenda for human– Martinuzzi, R., & Tropea, C. (1993). The Flow Around Surface-Mounted, Prismatic Obstacles Placed in a Liu, M., Zhang, Q., Fan, F., & Shen, S. (2018). Experiments on natural snow distribution around simplified Berends, Berends, K. D., Scheel, F., Warmink, J. J., de Boer, W. P., Ranasinghe, R., & Hulscher, S. J. M. H. (2019). Keijsers, J. G. S., De Groot, A. V., & Riksen, M. J. P. M. (2016). Modeling the biogeomorphic evolution of Galiforni Silva, F., Wijnberg, K. M., de Groot, A. V., & Hulscher, S. J. M. H. (2019). The effects of beach width beach of effects The (2019). H. M. J. S. Hulscher, & V., A. Groot, de M., K. Wijnberg, F., Silva, Galiforni (2019). C. Hallin, Jackson, N. L., & Nordstrom, K. F. (2011). Aeolian sediment transport and landforms in managed coastal

RIUS 7: BUILDING WITH NATURE PERSPECTIVES 258 BEACH-DUNE MODELLING IN SUPPORT OF BUILDING WITH NATURE FOR AN INTEGRATED SPATIAL DESIGN OF URBANIZED SANDY SHORES 259 , - 139 , , 101- 7, , 102–110. 110 , (Vol. 171, pp. 11–27). pp. (Vol. 171, (pp. 1693–1707). World Coastal Engineering Coastal 17(1–3), 29–46. https://doi. Coastal Engineering Research in Urbanism Series, Research in , 63–74. https://doi.org/10.1016/j. 63–74. 95, , , 98–112. https://doi.org/10.1016/j.env 98–112. , 115 Geomorphology, Report Internship at Hoogheemraadschap Hol- (36), papers.100. https://doi.org/10.9753/icce.v36. papers.100. 1(36), , Coastal Dunes. Ecological Studies Coastal Dunes. Ecological Building and Environment Building and Analysing measures improve beach-duneto interaction in the presence of man- Juli 2017 Zandmotor vanuit noord Juli 2017 [Photograph]. Flickr. https://www.flickr.com/ , Software & Environmental Modelling Coastal Engineering Proceedings Engineering Coastal Coastal Engineering 1990 (pp. 2087-2100). Coastal Sediments 2019: Proceedings of the 9th International Conference Coastal Sediments 2019: https://doi.org/10.1016/j.coastaleng.2016.01.005 shores. urbanized at formation dune for principles design towards soft.2019.02.010 sandy barrier island with a buried seawall during Hurricane Sandy. Seawall Test Case. Test Seawall Scientific. https://doi.org/10.1142/9789811204487_0146 ment. In M. L. Martínez & N. P. Psuty (Eds.), Springer. https://doi.org/10.1007/978-3-540-74002-5_2 models. cess-based 128. https://doi.org/10.47982/rius.7.130 made structures using computational fluid dynamics (CFD). lands Noorderkwartier. University of Utrecht. B.L. Edge (Ed.), of nature-based flood defenses: Dealing with extremes and uncertainties. 47–64. https://doi.org/10.1016/j.coastaleng.2018.05.002 ics: evidence from field and wind tunnel measurements. org/10.1016/0169-555x(95)00093-k photos/zandmotor/35632520843/ papers.100 angles. pitch different having roofs bled buildenv.2015.09.014 Vallee M. & Rosati, D. J. Wang, P. In beach. the on buildings by created patterns erosion and deposition (Eds.), Van Bergen, J., Mulder, J., Poppema, D, Nijhuis, S., Wijnberg, K. & Kuschnerus, M. (2021). Urban dunes: Smallegan, S. M., Irish, J. L., Van Dongeren, A. R., & Den Bieman, J. P. (2016). Morphological response of a of response Morphological (2016). P. J. Bieman, Den & R., A. Dongeren, Van L., J. Irish, M., S. Smallegan, Muller, Muller, J., Figlus, J., & de Vries, S. (2018). Xbeach Simulation of Hybrid Coastal Protection: A Galveston Psuty, N. P. (2008). The Coastal Foredune: A Morphological Basis for Regional Coastal Dune - Develop Roelvink, D., & Costas, S. (2019). Coupling nearshore and aeolian processes: XBeach and duna pro- Van Onselen, E. P. (2018). Visser, P. J., Vrijling, J. K., & Verhagen, H. J. (1991). A field experiment on breach growth in sand-dikes. In Vuik, V., van Vuren, S., Borsje, B. W., van Wesenbeeck, B. K., & Jonkman, S. N. (2018). Assessing safety Wiggs, G. F. S., Livingstone, I., & Warren, A. (1996). The role of streamline curvature in sand dune dynam- dune sand in curvature streamline of role The (1996). A. Warren, & I., Livingstone, S., F. G. Wiggs, Zandmotor. (2017, July 9). Ozmen, Y., Baydar, E., & van Beeck, J. P. A. J. (2016). Wind flowover the low-rise building models with- ga Poppema, D. W., Wijnberg, K. M., Mulder, J. P., & Hulscher, S. J. (2019, May). Scale experiments on aeolian on experiments Scale May). (2019, J. S. Hulscher, & P., J. Mulder, M., K. Wijnberg, W., D. Poppema,

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