Seabed roughness in the dynamic near‐shore environment is continuously modified by the interplay of physical and biological processes including bedform morphodynamics and bioturbation. We introduce a novel regime‐state framework to determine the dominant modifier of seabed roughness based on observed or estimated physical forcing, which are classified by critical Shields parameter or wave mobility thresholds. The regime‐state framework is applied to a set of field observations containing time‐lapse sonar imagery of ripple growth, decay, and bioturbation. The rate of ripple decay varies in both physical and biological processes. The decay rate is sensitive to oscillatory forcing magnitude and direction relative to relict ripple orientation and time‐evolving ripple height. We found two distinct episodes of ripples decayed by 20%–30% within 4–5 days. Ripple decay models and observations did not agree in rate of decay up to and following the same time period. By varying decay rate using a time‐dependent diffusion coefficient determined by the dominant decay mechanism, the regime‐state framework resulted in better agreement to field observations. Benthic megafauna are also shown to create seabed roughness, excavating dense fields (>1 pit/m²) of pits (≤84 cm in diameter) that introduce acoustic roughness comparable to 8–12 cm high ripples. The spatiotemporal variability of megafaunal pit formation suggests diffusion‐based bioturbation models are not adequate and megafaunal pits require additional parameterization to mechanistically model. The regime‐state framework presented in this study serves as a framework for future investigations and modeling of ripple morphodynamics, bioturbation, and roughness.

中文翻译：

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海底粗糙度形态动力学模型的制度状态框架

物理和生物过程（包括床形形态动力学和生物扰动）的相互作用不断改变着动态近岸环境中的海床粗糙度。我们引入了一种新颖的状态状态框架，可以根据观测到的或估计的物理强迫来确定海床粗糙度的主要修正量，并根据关键的Shields参数或波迁移率阈值对其进行分类。政体状态框架应用于一组现场观测，其中包含波纹增长，衰减和生物扰动的延时声纳图像。纹波衰减的速率在物理和生物过程中均变化。衰减速率对振荡强迫的大小和方向（相对于遗迹波纹方向和随时间变化的波纹高度）敏感。我们发现在4-5天内，两个明显的涟漪发作衰减了20％-30％。波纹衰减模型和观测值在同一时间段之前和之后的衰减率不一致。通过使用由主导衰变机制确定的时间相关扩散系数来改变衰变速率，政体状态框架与实地观测结果具有更好的一致性。底栖大型动物也被证明会造成海床的不平整，挖掘密集的田地（> 1 pit / m²）凹坑（直径≤84cm），其声音粗糙度可与8–12 cm的高纹波相媲美。巨型动物坑形成的时空变化表明，基于扩散的生物扰动模型是不够的，巨型动物坑需要附加的参数来进行机械建模。本研究中提出的状态状态框架可作为未来研究和波纹形态动力学，生物扰动和粗糙度建模的框架。