Presence Of Seawall Research Articles

Interaction of surface water waves with partial porous structure and floating elastic plate in the presence of sea wall

ABSTRACT This study proposes a model composed of either bottom-standing porous structure (BSPS) or surface-piercing porous structure (SPPS) in combination with an elastic plate (EP) placed at a distance from one another to protect a sea wall. The study uses the governing equation and the boundary conditions to coin a system of equations, and the system of equations is solved to identify the hydrodynamics coefficients. Further, it is noticed that length, frictional coefficient, porosity of the porous structure, and flexural rigidity of EP play a crucial role in reducing the force on the sea wall, water elevation and plate deflection. The SPPS exhibits a nearly 60% reduction in wall force coefficient due to a 50% increase in wave-damping when compared to BSPS for k 0 H = 0.85. These results are crucial for developing floating structures that can resist harsh wave environments and minimize the effects of waves close to the shore.

Myrtle Beach: A history of shore protection and beach restoration

The City of Myrtle Beach (South Carolina, USA) initiated a three-phase plan for beach restoration in the 1980s: Phase 1 — small-scale beach scraping; Phase 2 — mediumscale nourishment by trucks using inland sand; and Phase 3 — large-scale nourishment by dredge using offshore sand. Phases 1 and 2 were locally funded and served as interim measures (1981-1996) until a 50-year federal project could be constructed (1997 to present). In the course of this work, the city pioneered several approaches to beach management and became a model for the state. These include: the prototype SC beach survey program; the profile volume method for determining shorelines in the presence of seawalls, which was codified in the Beach Management Act (BMA) of 1988; the first locally funded nourishment (1986-1987) and FEMA-funded postdisaster renourishment after Hurricane Hugo 1989-1990; and the first surveys of offshore deposits for nourishment. Before restoration, nearly 65% of the 9-mile (14.5 kilometer) oceanfront was armored with seawalls, bulkheads, and revetments (1981). After nourishment, erosion control structures are now buried and fronted by a vegetated storm berm, while a wider beach accommodates millions of visitors each year. Total volumes and adjusted costs of nourishment from 1986 to early 2018 are 4,997,201 cubic yards (3,820,360 m3) and ~$70.8 million ($2018), respectively. On a unit annual beach length basis, the cost of beach restoration and improvement has averaged $46.80 per one foot of shoreline per year (~$153.50/m/yr) ($2018). Oceanfront property values on a unit length of shoreline basis presently range from ~$15,000/ft (~$49,200/m) for single-family homes to ~$75,000/ft (~$250,000/m) for high-rise buildings, suggesting that beach maintenance has cost well under 0.5% of oceanfront property values per year. Sand loss rates have averaged ~0.8 cy/ft/yr (2.0 m3/m/yr), and the rate of nourishment has been more than adequate to keep up with the ~0.37 ft (0.11 m) sea level rise between 1980 and 2018.

Physical model study of beach profile evolution by sea level rise in the presence of seawalls

Persistent and accelerating sea level rise (SLR) may have a significant impact on the evolution of sandy coastlines this Century. The response of natural sandy beaches to SLR has been much discussed in the literature, however there is a lack of knowledge about the impact of SLR on engineered coasts. Laboratory experiments comprising over 320 h of testing were conducted in a 44 m (L) x 1.2 m (W) x 1.6 m (D) wave flume to investigate the influence of coastal armouring in the form of seawalls on coastal response to SLR. The study was designed to investigate the effects of contrasting types of seawalls (reflective-impermeable versus dissipative-permeable) on beach profile response to increased water levels, in the presence of both erosive and accretionary wave conditions. The results obtained showed that seawalls alter the evolution of the equilibrium profile with rising water level, causing increased lowering of the profile adjacent to the structure. Under erosive wave conditions, modelled profiles both with and without seawall structures in place were observed to translate landward in response to SLR and erode the upper profile. It was found that the erosion demand at the upper beach due to a rise in water level remains similar whether a structure is present or not, but that a seawall concentrates the erosion in the area adjacent to the seawall, resulting in enhanced and localised profile lowering. The type of structure present (dissipative-permeable versus reflective-impermeable) was not observed to have a significant influence on this response. Under accretive conditions, the preservation of a large shoreface and berm resulted in no wave-structure interaction occurring, with the result that the presence of a seawall had no impact on profile evolution. A potential two-step method for estimating the observed profile response to water level rise in the presence of seawalls is proposed, whereby a simple profile translation model is used to provide a first estimate of the erosion demand, and then this eroded volume is redistributed in front of the seawall out to the position of the offshore bar.

DUNE EROSION NEAR SEA WALLS: MODEL-DATA COMPARISON

This paper describes the validation of the dune erosion model XBeach with laboratory measurement data of dune erosion in the presence of sea walls and revetments. Simulation results show that the essential dune set back processes are captured by the model and that the measurements at most locations are approximated quite well. Some aspects however
 need more attention in further research. The alongshore distance from a fixed structure over which the dune erosion is influenced was not well captured by the model. Also the absence of short wave run-up on the revetment still causes an underestimation of the amount of dune erosion above the revetment. Furthermore the influence of the angle of incidence
 was investigated with a conceptual model approach. This revealed a relatively high influence of the angle of incidence on the governing flow pattern in front of a transition between a dune and a fixed structure.

Erosion and Accretion of a Placer Mining Beach of SW Indian Coast

The erosion/accretion pattern in a placer mining beach on the southwest Indian coast was monitored for five years to study the role of different driving forces. The beach has maximum width during the fair weather months and least in the rough monsoon months. Apart from hydrodynamic processes, sand mining and presence of sea wall are found to be the driving forces for erosion/accretion. Impact of sand mining is not felt on the beach when the mining is within an optimum level, equivalent to the natural replenishment. It is concluded that, though sand mining will cause erosion in the innershelf, the time taken for a measurable impact can be long if the mining volumes are much less than the annual volume changes.

Closure: Beach Nourishment in Presence of Seawall

Closure: Beach Nourishment in Presence of Seawall

Discussion: Beach Nourishment in Presence of Seawall

Discussion: Beach Nourishment in Presence of Seawall

Beach Nourishment in Presence of Seawall

Beach nourishment, placed along a seawalled shoreline, can exhibit a markedly different behavior than projects on shorelines with adequate compatible sands to transport. The most striking effects of engineering significance are: (1) The migration of the centroid of the nourishment planform anomaly when acted on by oblique waves; and (2) a potentially different (currently unknown) rate of spreading of the planform anomaly. Under the most idealized considerations of uniform transport along the nourished shoreline, the speed of centroid migration is shown to increase as the planform anomaly spreads out under the mobilizing action of the waves, and the rate at which the planform spreading (dispersion) occurs is not affected by the seawall. Also, for normally incident waves, the seawall does not affect the planform evolution. Analytical, numerical, and experimental approaches are employed to demonstrate the aforementioned effects. It is shown that the transport at the ends of the project, where all the nourish...

Foreword

Persistent and accelerating sea level rise (SLR) may have a significant impact on the evolution of sandy coastlines this Century. The response of natural sandy beaches to SLR has been much discussed in the literature, however there is a lack of knowledge about the impact of SLR on engineered coasts. Laboratory experiments comprising over 320 h of testing were conducted in a 44 m (L) x 1.2 m (W) x 1.6 m (D) wave flume to investigate the influence of coastal armouring in the form of seawalls on coastal response to SLR. The study was designed to investigate the effects of contrasting types of seawalls (reflective-impermeable versus dissipative-permeable) on beach profile response to increased water levels, in the presence of both erosive and accretionary wave conditions. The results obtained showed that seawalls alter the evolution of the equilibrium profile with rising water level, causing increased lowering of the profile adjacent to the structure. Under erosive wave conditions, modelled profiles both with and without seawall structures in place were observed to translate landward in response to SLR and erode the upper profile. It was found that the erosion demand at the upper beach due to a rise in water level remains similar whether a structure is present or not, but that a seawall concentrates the erosion in the area adjacent to the seawall, resulting in enhanced and localised profile lowering. The type of structure present (dissipative-permeable versus reflective-impermeable) was not observed to have a significant influence on this response. Under accretive conditions, the preservation of a large shoreface and berm resulted in no wave-structure interaction occurring, with the result that the presence of a seawall had no impact on profile evolution. A potential two-step method for estimating the observed profile response to water level rise in the presence of seawalls is proposed, whereby a simple profile translation model is used to provide a first estimate of the erosion demand, and then this eroded volume is redistributed in front of the seawall out to the position of the offshore bar.