A Stochastic Approach to Modeling Tidal Creek Evolution: Exploring Environmental Influences on CreekTopologies Through Ensemble Predictions

Abstract

A numerical tool integrating hydrodynamics, vegetation growth, stochastic selection, and Monte-Carlo simulation is developed to predict channel network evolution in a newly inundated backbarrier wetland. Focusing on the formation and evolution of tidal channels, model simulations suggest a clear tendency towards specific creek topologies with high probability despite creek evolution being subject to random perturbations. These creek topologies are primarily determined by wetland topography while the influence of vegetation is secondary. Ensemble results of Monte-Carlo simulations identify threshold points leading to bimodal separation of the emergent creek networks characterized by different complexity and efficiency. This, in turn, assists the recognition of necessary human interventions to encourage the formation of complex and far-reaching creek networks that can promote exchange of materials between estuaries and salt marshes and, hence, maintain salt marsh ecosystem structure and function.Plain Language Summary A large part of the world's low-lying areas is heavily managed to protect lives, assets, and landscapes from marine-derived natural hazards. However, climate change is putting unprecedented pressure on these managed environments, forcing the adoption of "no active intervention" or "managed realignment" strategies in areas where "hold the line" options cannot be justified due to financial constraints. This leads to the very likely possibility that unmaintained coastal defenses will begin to fail, raising questions as to the potential impacts on low-lying regions as well as the options available to mitigate impacts through targeted interventions. Of particular interest is the question of whether it is possible to facilitate the shift of managed coastal wetlands towards intertidal environments in which tidal creeks form and evolve to support salt marshes. Combining the use of a numerical model and multiple model runs, we find that although the evolution of tidal creeks is subject to random disturbances, creek networks are likely to form with a clear tendency towards specific types. Grouped results of multiple, random simulations are useful in identifying interventions that are necessary for developing far-reaching tidal creek networks. Influence of vegetation is found to be secondary compared to the wetland topography in terms of influencing tidal creek evolution.

Study on the Influence of Salt Marsh Vegetation on Tidal Current and Sediment Transport in Intertidal Zone

“…In order to accelerate the evolution of landforms and make the evolution results more natural, this model uses an initial disturbance of 0.1 m terrain. According to Li et al' s research, although tidal flats evolve under random disturbance, there is still a clear trend of evolution to a specific topology, and it has a high probability [8]. In this study, the geomorphic acceleration factor is 73, and the geomorphic evolution lasts for 3 years.…”

Intertwined Eco‐Morphodynamic Evolution of Salt Marshes and Emerging Tidal Channel Networks

“…The evolution of tidal flats and salt marshes is strongly related to tidal channel dynamics. Both tidal channel and intertidal platform evolution are governed by the interactions between hydrodynamics, sediment transport, morphological changes, and biological effects (Alizad, Hagen, Morris, Bacopoulos, et al., 2016; D'Alpaos et al., 2007; De Swart & Zimmerman, 2009; Gong et al., 2018; Li et al., 2019; Temmerman et al., 2007; Vandenbruwaene et al., 2011; Zhao et al., 2019). The mutual feedbacks (either positive or negative), which characterize these interactions, control the so‐called Morphodynamic Loop (Coco et al., 2013; Cowell & Thom, 1994; Wright & Thom, 1977).…”

Biotic and abiotic factors control the geomorphic characteristics of channel networks in salt marshes

“…Tidal channel networks are typical morphological features of coastal landscapes. They promote exchange of materials (water, sediments, nutrients, biota) between coastal marshes and the open sea, hence maintaining the structure and function of salt marshes (Vandenbruwaene et al 2012;Kearney and Fagherazzi 2016;Li et al 2019). A comprehensive understanding of the initial formation and long-term evolution of channel networks is fundamental to address their response to climate change and human interference (Kearney and Fagherazzi 2016;Schwarz et al 2018).…”

“…Previous studies revealed that the formation, deepening, and expansion of channel networks are facilitated with high tidal ranges and low water depths (Kirwan and Guntenspergen 2010;Stefanon et al 2010;Van Maanen et al 2013). There is, however, growing recognition that vegetation-landform interactions play a key role in shaping intertidal landscapes (Coco et al 2013;Vandenbruwaene et al 2013;Schwarz et al 2018), although some studies suggest that the influence of vegetation is only secondary (Li et al 2019). In general, several numerical model studies have reported enhanced channel formation due to vegetation in early stages of development (D'Alpaos et al 2007;Schwarz et al 2014;Bij de Vaate et al 2020), but they did not consider later stages of channel evolution.…”

“…It is now widely accepted that the formation and evolution of channel networks result from the interactions between hydrodynamic conditions (e.g., tidal currents, waves, tidal prism), geomorphic characteristics (e.g., elevation, slope, coastal alignment, sediment properties) and vegetation traits (e.g., aboveground and belowground biomass, stem density, height, and diameter) (Schwarz et al 2018;Li et al 2019). These factors govern the balance between erosion and deposition and vary across channel network systems.…”