Placement, porosity and randomness of cube and Cubipod armor layers

Although little attention is usually given to the armor porosity and armor randomness of randomly placed concrete armor units in mound breakwaters, significant model effects may occur if armor porosity and randomness are different for prototype and small-scale models. Armor randomness and porosity are easier to control in small-scale models because they are generally constructed by hand in dry and perfect viewing conditions; equipment and environmental constraints make control at prototype scale more difficult. Results from three-dimensional small-scale placement tests are analyzed when cube and Cubipod units are placed with a small-scale crawler crane and pressure clamps. Armor porosity was not workable below 37% for cubes and 35% for Cubipods; placement grids were obtained for feasible armor porosities, considering row settlements during construction as well. Amethodology to measure armor randomness using high-precision laser scanning, similar to terrestrial LIDAR, was tested with small-scale cube and Cubipod armor. Three armor randomness indexes (ARIs) measured the randomness of cube and Cubipod armor; the values for ARIs were higher for Cubipod armor than for cube armor. (C) 2014 American Society of Civil EngineersThe authors would like to acknowledge the financial support received from the CDTI (CUBIPOD and CLIOMAR Projects), SATO-OHL Group (CLIOMAR Project), and the Spanish Ministry of Economy and Competitiveness (Grant BIA2012-33967). The third author was financially supported through the FPU program (Formacion del Profesorado Universitario) funded by the Spanish Ministry of Education (Ministerio de Educacion, Cultura y Deporte). The authors thank Tomas J. Perez for assisting with the 3D placement tests and processing the laser-scanner data, and Debra Westall for revising the manuscript.Pardo De Gregorio, V.; Herrera Gamboa, MP.; Molines Llodra, J.; Medina Folgado, JR. (2014). Placement, porosity and randomness of cube and Cubipod armor layers. Journal of Waterway, Port, Coastal, and Ocean Engineering. 140(5). doi:10.1061/(ASCE)WW.1943-5460.0000245S140

Toe berm design for very shallow waters on steep sea bottoms

The toe berm is a relevant design element when rubble mound breakwaters are built on steep sea bottoms in breaking conditions. Different design formulas can be found in the literature to predict the damage caused to submerged toe berms placed on gentle bottom slopes. However, these formulas are not valid for very shallow waters in combination with steep sea bottoms where toe berms receive the full force of breaking waves. To guarantee breakwater stability in these conditions, new design formulas are needed for toe berms. To this end, physical model tests were carried out and data were analyzed to characterize rock toe berm stability in very shallow water and with a bottom slope m = 1/10. Based on test results, a new formula was developed with three parameters to estimate the nominal diameter (Dn50) of the toe berm rocks: water depth at the toe (hs), deep water significant wave height (Hs0), and deep water wave length (L0p).The first author was financially supported through the FPU program (Formacion del Profesorado Universitario) funded by the Spanish Ministry of Education (Ministerio de Educacion, Cultura y Deporte) FPU13/01872. The authors also acknowledge financial support from the Spanish Ministry of Economy and Competitiveness (grant BIA2012-33967). The authors thank Debra Westall for revising the manuscript.Herrera Gamboa, MP.; Medina Folgado, JR. (2015). Toe berm design for very shallow waters on steep sea bottoms. Coastal Engineering. 103:67-77. https://doi.org/10.1016/j.coastaleng.2015.06.005S677710

Bank Erosion Processes in Regulated Navigable Rivers

Vessel-induced waves affect the morphology and ecology of banks and shorelines around the world. In rivers used as waterways, ship passages contribute to the erosion of unprotected banks, but their short- and long-term impacts remain unclear. This work investigates the effects of navigation on bank erosion along a reach of the regulated Meuse River with recently renaturalized banks. We apply UAV-SfM photogrammetry, RTK-GPS, acoustic Doppler velocimetry, aerial and terrestrial photography, soil tests, and multibeam echosounding to analyze the progression of bank retreat after riprap removal. After having analyzed the effects of ship-generated waves and currents, floods, and vegetation dynamics, a process-based model is proposed to estimate the long-term bank retreat. The results show that a terrace evolves in length and depth across the bank according to local lithology, which we clustered in three types. Floods contribute to upper-bank erosion-inducing mass failures, while near-bank flow appears increasingly ineffective to remove the failed material due to terrace elongation. Vegetation growth at the upper-bank toe reduces bank failure and delays erosion, but its permanence is limited by terrace stability and efficiency to dissipate waves. The results also indicate that long-term bank retreat is controlled by deep primary waves acting like bores over the terrace. Understanding the underlying drivers of bank evolution can support process-based management to optimize the benefits of structural and functional diversity in navigable rivers.Rivers, Ports, Waterways and Dredging EngineeringEnvironmental Fluid MechanicsCoastal Engineerin