M. Sedat Kabdasli

Cross-Shore Sorting on a Beach under Wave Action

Abstract Sorting of sediment on a beach occurs when the cross-shore profile consists of graded sediments. Each grain-size fraction within a mixture responds differently to the same hydrodynamic regime. Sorting of sediment under wave action takes several forms. Stratified layers of finer and coarser sediment are formed, depending on wave climate, grain size, and beach slope. Grain size and sorting studies are of great importance in characterizing the dynamic beach environment. Some field data have been reported in the literature. In the present study, the cross-shore distribution of sediments, as well as the corresponding beach profiles, were measured in a wave basin on 1:5 beach slope for regular waves. Eighteen sets of experiments were performed on cross-shore sorting mechanisms using two different sand beds. The sorting of bed material and the formation of armor coats along beach profiles were defined by grain-size distribution and dimensionless parameters in this study. The experiments showed that finer material was deposited on the crest of bar-type beach profiles, but coarser grains accumulated on the foreshore, trough, ridge, and toe sections. Finer materials settled on the foreshore and crest of step-type profiles while coarser grains were deposited on the ridge and toe sections. The effect of the movement of a particular fraction on the sediment transport rate was also studied. Calculated sediment transport, modified to include the effects of sorting, was compared with transport rates measured in the wave basin. This suggested that the results under the experimental conditions were satisfactory for the description of sediment transport in the surf zone using the partial sediment transport mechanism over the beach profiles.

The effect of an emergent vegetation (i.e. Phragmistes Australis) on wave attenuation and wave kinematics

ABSTRACT Akgul, M.A., Yilmazer, D., Oguz, E., Kabdasli, M.S., Yagci, O., 2013. The effect of an emergent vegetation (i.e. Phragmistes Australis) on wave attenuation and wave kinematics Coastal vegetation acts as a natural barrier at many coastal zones, protecting the landside against wave effects and coastal erosion. It is known that coastal vegetation affects wave properties, and studies regarding this topic have been made in a wide variety, mostly focusing on wave attenuation. In this study, laboratory experiments have been conducted in a wave basin to inspect the effect of an emergent vegetation on wave attenuation, wave transformation and wave kinematics. A blank area is present along the reed field, which enables energy transformation during wave propagation. Three different regular waves have been sent to a natural reed field, and wave heights and kinematics have been measured around the structure. The results indicate that crest-parallel energy transmission takes place as the waves propagate along the reed field, which is boosted at the end of the reed, and the transmission becomes faster on waves with higher wave steepness. Measured water particle velocities have been evaluated to obtain the steady-cyclic and fluctuation components, by which, turbulence intensities in front and at the wake of the reed field have been evaluated. The results indicate that turbulence intensity increases at the mid-depth at the wake of the structure, becoming higher with increasing wave steepness. Thus, one may conclude that energy dissipation takes further place after the end of the reed field due to turbulence.

The effect of reed beds on wave attenuation and suspended sediment concentration

ABSTRACT Oguz, E., Elginoz, N., Koroglu, A., Kabdasli, M.S., 2013. The effect of reed beds on wave attenuation and suspended sediment concentration. The effect of emergent and submerged vegetation on uniform and oscillatory flow conditions has been intensively studied by researchers in the last two decades. It has been determined that vegetation affects wave characteristics and cause wave attenuation especially in shallow waters where wave orbitals are in interaction with vegetation. Consequently they affect sediment deposition and resuspension acting as a sink. The aim of this study is to determine wave attenuation due to vegetation, and to identify the effect of emergent vegetation on suspended sediment concentration. In this experimental study, a reed bed was established on a sandy bottom in a wave flume in ITU Hydraulics Laboratory. Regular waves with different wave steepness were generated in the flume and water surface elevations through the reed bed were measured using resistance type wave gauges. Suspended sediment concentration time series were measured using OPCON along depth. The gradual wave attenuation due to reed bed was determined and wave transmission coefficients for different waves were found between 0.35 and 0.55 and these values are reversely proportional with wave steepness. It has been found out that wave attenuation also decreases with increasing KC numbers. Suspended sediment concentration measurements inside the reed bed were a little bit harder to interpret, but a decrease in concentration; before the waves reach the reed bed and after the waves left the reed bed, was determined. In spite of many studies on effects of vegetation on flow conditions there is still a lack of understanding vegetation-flow interaction and sedimentation around them. This study is an attempt to make a contribution on this topic.

EXPERIMENTAL INVESTIGATION ON SOLITARY WAVE RUN-DOWN AND ITS EFFECTS ON ARMOR UNITS

In this paper, solitary wave run-down height and the geometric characteristics of solitary wave-induced strewing of armor units are investigated. In the experiments, natural sand and grain having different diameters are used. Run-down heights for not armored and armored beaches are evaluated and empirical formulas are suggested. From the results of these experiments, it was observed that armor units caused a decrease of approximately 35% run-down height. The relation between the run-up and run-down height is given by a formula. Subsequently, the area along the slope that had to be protected (such as a pipeline) was to be considered. In the experiments, this area was protected in two different ways (Alternative I, Alternative II). The strewing of the armor units forming the protective layer was studied. It is concluded that Alternative II is more suitable than Alternative I for protected area. The most important variables strewing of armor units were defined by using experimental results. These variables are written as a dimensionless group named as pax 3 by using π theory. The empirical formulas between the geometric characteristics of strewing of armor units and dimensionless group are proposed through regression analysis.

An Oil Spill and Response Activities Scenarios After the Fuel Tank Seepage in a Port: Haydarpasa Port Case Study

Oil spills due to the marine related facilities have been accepted as human sourced catastrophes. The cleanup and recovery from oil spills are generally modeled with the help of numerical models. The type of oil spilled, the water temperature, the dominant winds and currents, and the types of shorelines involved are used as the key parameters of the oil spill modeling systems. The numerical studies are efficiently used to predict the fate of released oil and the containment methods. In this study, several scenarios for the recovery from the oil spill are modeled in Haydarpasa Port as a case study. Haydarpasa port, which is located on the Anatolian side of Bosporus in Istanbul, serves a hinterland for the most industrialized area of Turkey. Both the oil spill and the response activities scenarios are modeled using OILMAP™ Version 6.1. Surface Trajectory Model and the Stochastic Model for seepage from the fuel tank for varying spill duration periods and for the same environmental conditions. In this study, seepage from a fuel tank and the most efficient response activity in a port are modeled as an emergency plan in Haydarpasa port as a case study.Copyright

Wave Damping and Retardance by Emergent Vegeatation

Although in the past great attention has been devoted to coastal stabilization, the effect of aquatic vegetation on wave characteristics (damping and retardance etc) is still not well known. In this context an experimental study was performed in an irregular wave flume to explore the effect of reeds (phragmites australis) on wave damping and retardance. Further for a given vegetated area the effect of wave characteristics (i.e. wave height, wave period and wave steepness) on wave damping and retardance were discussed. Real reeds (phragmites australis) with diameter less than 5 mm were employed throughout the experiments for the emergent case. A dimensionless number was introduced to characterize both the vegetated area magnitude and the effect of the vegetation on wave damping and retardance.

Monitoring Differential Urbanization to Integrate with Basin Management and a Basin Information System Modeling for Istanbul

This article intends to give the outline of a basin information system to be generated and managed in order to monitor the increase of urbanization and trend of pollution potential over seven major basins (watersheds) of Istanbul, Turkey. The data from basin monitoring studies of Istanbul Water and Wastewater Management Authority (Istanbul) was used to evaluate the differential settlement and construction. After the urbanization increase is evaluated by means of building/facility areas, the pollution trends are assessed for different time intervals in terms of five parameters by making certain unit load assumptions. The results indicate that residential settlement increased 0.124–0.003% during 29 months. Also in the same period, mean pollution potential of the basins is found to increase 8.747, 3.578, 5.970, 0.922, and 0.145 in terms of tons/day for Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD5), Suspended Solids (SS), Total Kjeldahl Nitrogen (TKN), and Total Phosphorus (TP), respectively, considering domestic wastewater and diffuse pollution loadings (from urban runoff and feedlots). These results state that monitoring of basins, especially those exposed to intense urbanization, must be conducted periodically and continuously by means of the basin information system as the first step to be able to control the pollution and to take measures against the threats that come with urbanization.