Sandy subtidal sediments are part of the earth's largest filter system. Water flow through bottom sediments is driven by wave action on the sea surface. The mechanisms involved are described, including a theoretical deduction and field measurements. As an example, the total water exchange through part of the West Atlantic shelf is computed and the influence of the phenomenon is discussed from a biological point of view and with regard to its importance for the world's oceans.

The subtidal pump: a mechanism of interstitial water exchange by wave action

The main problem dealt with in this thesis is the calculation of certain effects caused by random waves breaking on a slope. The solution to this problem is greatly complicated by the fact that wave breaking is a highly nonlinear process. The flow field is further complicated by far stronger in homogeneities than those occurring outside the breaker zone, by air entrainment and by generation of turbulence. No realistic deductive treatment of it has been developed so far. Even for the simpler case of periodic waves, empirical knowledge of certain macroscopic properties of the breakers is still an integral part of calculations relating to the surf zone. An attempt has been made in this thesis to apply this knowledge in a formulation incorporating the stochastic nature of wind-generated waves. The computations are of two distinct categories, those relating to comparatively gentle slopes and those relating to comparatively steep slopes. A summary of the results will be given in the following. The energy variation is calculated in chapter 5 by clipping a fictitious wave height distribution, which theoretically would be present if breaking did not occur, at an upper limit which is determined from an adapted breaking criterion for periodic waves. The computed results are in fair agreement with measurements carried out on a plane slope. Knowledge of the energy variation permits the radiation stresses to be evaluated, which in turn are necessary for the calculation of the set-up and the longshore current velocity profiles. A comparison of the calculated set-up profiles with empirical data has not given conclusive results. Good agreement has been found with field data, but not with laboratory data, which locally showed a systematically smaller rise towards the shore than would be expected on the basis of the measured or calculated wave height variations. However, there is some uncertainty with respect to the system used for measuring the set-up in the laboratory, so that is not known to which extent the differences are real or apparent.

/pdf/computation-of-set-up-longshore-currents-run-up-and-2a5ny62dir.pdf

Computation of set-up, longshore currents, run-up and overtopping due to wind-generated waves

Climate change, environmental impact and the limited natural resources urge scientific research and novel technical solutions. The monograph series Green Energy and Technology serves as a publishing platform for scientific and technological approaches to "green" i.e. environmentally friendly and sustainable technologies. While a focus lies on energy and power supply, it also covers "green" solutions in industrial engineering and engineering design. Green Energy and Technology addresses researchers, advanced students, technical consultants as well as decision makers in industries and politics. Hence, the level of presentation spans from instructional to highly technical. **Indexed in Scopus**.

/pdf/green-energy-and-technology-2xuq1yllhb.pdf

Green Energy and Technology

Modeling the development of marine terraces on tectonically mobile rock coasts

A numerical technique is presented for computing radiance distributions in natural waters that have wind-blown surfaces and depth-dependent inherent optical properties. Input to the numerical model consists of the radiance distribution incident on the air-water surface from above, the wind velocity, which specifies the state of randomness of the air-water surface via a wind speed-wave slope spectrum, the volume scattering and volume attenuation functions of the water body as functions of depth and wavelength, and the type of bottom boundary. Primary output from the model consists of directionallv discretized radiances as functions of wavelength, direction, and depth throughout and above the water body. General knowledge of the radiance distribution in a water body is a prerequisite for solving more specific problems, such as those occurring in studies of underwater visibility, remote sensing of the oceans from aircraft or satellites, heating of the upper layers of the oceans, or photosynthesis. Moreover, since radiance is the fundamental radiometric quantity, if the radiance is known then all other quantities of interest, such as the irradiance, are easily obtained. Unfortunately, measurement of radiance is a difficult and expensive task in the ocean environment, and few systematic studies of radiance have been made in natural waters. However, a numerical model has been developed for computing radiance distributions in natural hydrosols, such as lakes and seas, given the inherent optical properties of the hydrosol itself and appropriate boundary conditions at the surface and bottom of the water body, along with the radiance incident on the water surface. This

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1989.34.8.1473

Gerhard Neumann

Papers

On ocean wave spectra and a new method of forecasting wind generated sea