A method to estimate the longshore sediment transport at ebb‐tidal deltas based on their volumetric growth: Application to the Guadiana (Spain–Portugal border)

Abstract

Current techniques assessing longshore sediment transport rates have large uncertainties, pleading for the development of alternative and complementary approaches. The present study proposes a method to estimate the decadal average rate of longshore transport at modern ebb‐tidal deltas based on a sediment budget analysis of the outer shoal growth. This transport is obtained as the balance of the other contributions to the shoal with the total sediment input rate obtained from an inverse application of the inlet reservoir model. The method is applied to the Guadiana ebb‐tidal delta, yielding an average longshore sediment transport rate (~85 000 m3 year−1) in good agreement with expectations for the region. It is exemplified that this decadal averaged rate can be used to improve longshore sediment transport expressions in order to study its variability over shorter time scales. At the Guadiana, the yearly longshore sediment transport from the improved formula ranges from ~25 000 m3 (westward) to ~245 000 m3 (eastward) and is related to the North Atlantic Oscillation index. Overall, the proposed method constitutes an alternative tool to constrain the average longshore sediment transport rate over decades in the vicinity of tidal inlets. It is applicable to ebb‐tidal deltas where the outer shoal growth (from an early to a mature stage) is well documented by bathymetric maps, and where the main transport pathways towards the outer shoal can be specified. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.

Dynamics and sedimentary assessment of a rock-bounded estuary: a case study—Tina Mayor (NW Spain, Iberian Peninsula)

“…As transitional coastal zones, estuaries are of great environmental importance and are protected by a variety of environmental institutions (Ramsar Convention, Special Protection Areas-SPA, and Sites of Community Importance-SCI) and have, therefore, been studied from different points of view. Geomorphological and sedimentological studies have been published focussing on the southern Iberian Peninsula, specifically Huelva and the south coast of Portugal (Guadiana) (Borrego et al 2013;Ruiz et al 2013;Morales et al 2014Morales et al , 2015Sampath and Boski 2016;Garel et al 2019;Carro et al 2019), as well as works examining records of tsunamis dating back to the Holocene (Morales et al 2008;Lima et al 2010;Costa et al 2012). In the north, dynamics, sedimentology and geomorphology have been widely addressed such as in Vigo Ria (Perez-Arlucea et al 2005; Vilas et al 2019).…”

Beyond Human Interventions on Complex Bays: Effects on Water and Wave Dynamics (Study Case Cádiz Bay, Spain)

“…In recent years, numerous studies have been carried out in bays and estuaries in which impacts of human activities have been identified and characterized, such as those on the tidal amplitudes [9][10][11][12], nutrient transport [13] and morphodynamics [14][15][16]. Many of these analyses have been carried out using: (1) idealized box models based on volumetric changes [2,14,17,18]; or (2) numerical simulations of the changes expected after the implementation of human interventions with process-based models [1,12,16]. The main drawback of the latter is that these simulations require extensive calibration and validation which is not easy to perform [5].…”