• NEANIAS Underwater Research Community

This document is a final overall report on the assessment and evaluation of the NEANIAS UNDERWATER services mainly from user perspective, but also including their technical assessment. Assessment and evaluations processes have been performed for each of the UNDERWATER services release cycles (from release #1 to the latest release #3) involving users internal to the NEANIAS consortium as well as external to the consortium, mainly belonging to academic and research institutes. Also, user feedbacks have been collected and, finally, a technical assessment has been performed thanks to template checklists made available by WP7.

ABSTRACT. The relationship between instability indices and extreme daily rainfall over state of Rio Grande do Sul, Brazil, is studied, as well as the main differences between extreme and ordinary rainfall events. A total of 105 extreme and 342 ordinary rainfall events were identified in 2000-2009 period. Composites of atmospheric fields for up to two days prior to the events showed some important features that may be considered precursors for extreme rainfall in this region: a surface low-pressure center over Paraguay and northern Argentina, a more intense northerly flow in this region and, consequently, a large moisture flux convergence over southern Brazil, specially over state of Rio Grande do Sul. Correlations between instability indices and extreme rainfall showed statistically significant liner relationships for almost all instability indices. However, the small degree of correlations does not support any quantitative rainfall forecasting methodology based only on instability indices. Keywords : rainfall forecasting, atmospheric instability, composites, correlation. RESUMO. A relacao entre os indices de instabilidade e a chuva extrema sobre o estado do Rio Grande do Sul, Brasil, e estudada neste trabalho, bem como as principais diferencas entre eventos comuns e extremos de chuva diaria. Um total de 105 eventos extremos e 342 comuns foram identificados dentro do periodo de 2000 a 2009. Compostos de campos atmosfericos para ate dois dias anteriores aos eventos mostraram caracteristicas importantes que podem ser consideradas precursoras a chuva extrema nesta regiao: um centro de baixa pressao em superficie sobre o Paraguai e o nordeste da Argentina, um escoamento de norte mais intenso nesta regiao e, consequentemente, maior convergencia do fluxo de umidade sobre o sul do Brasil, especialmente sobre o estado do Rio Grande do Sul. As correlacoes entre os indices de instabilidade e a chuva extrema mostraram relacoes lineares estatisticamente significativas para quase todos os indices. Entretanto, o pequeno grau das correlacoes nao suporta qualquer metodologia de previsao quantitativa de chuva baseada somente em indices de instabilidade. Palavras-chave : previsao de chuva, instabilidade atmosferica, compostos, correlacao.

The performance of a sonar system operating in shallow water is closely linked to the properties of the seabed. At the same time the sensitivity of the acoustic signal (or background) to sediment properties gives an acoustic sensor the potential to measure precisely those properties that are needed to estimate sonar performance. Of particular interest in this context is reverberation from low frequency active sonar (LFAS), because of its wide area potential, and the single beam echo sounder, because of its almost universal availability. The potential of these two instruments to provide the necessary data for the purpose of LFAS performance prediction is explored. Particular emphasis is placed on exploiting their complementary nature. Relevant questions include: The echo sounder measures properties of the uppermost few centimetres of sediment. How can this be made relevant to LFAS, which is sensitive to properties on a depth scale of metres rather than centimetres? The echo sounder measures properties directly beneath the ship, and at normal incidence. How can this information be used when the LFAS attention is focussed on sound travelling several kilometres, at angles close to grazing incidence? The information content of signals from the two sensors is discussed, with a view to answering these and related questions.

The performance of a sonar system operating in shallow water is closely linked to the properties of the seabed. At the same time the sensitivity of the acoustic signal (or background) to sediment properties gives an acoustic sensor the potential to measure precisely those properties that are needed to estimate sonar performance. Of particular interest in this context is reverberation from low frequency active sonar (LFAS), because of its wide area potential, and the single beam echo sounder, because of its almost universal availability. The potential of these two instruments to provide the necessary data for the purpose of LFAS performance prediction is explored. Particular emphasis is placed on exploiting their complementary nature. Relevant questions include: The echo sounder measures properties of the uppermost few centimetres of sediment. How can this be made relevant to LFAS, which is sensitive to properties on a depth scale of metres rather than centimetres? The echo sounder measures properties directly beneath the ship, and at normal incidence. How can this information be used when the LFAS attention is focussed on sound travelling several kilometres, at angles close to grazing incidence? The information content of signals from the two sensors is discussed, with a view to answering these and related questions.

The application of acoustic methods for the classification of bottomhabitats is based mostly on the analysis of measured parameters without relating them to the bathymetric structure. Geological complexity and biological patterns are closely related to bathymetry. This paper presents a new approach to the acoustic classification of bottom habitats in that it combinesthe distribution of a selected acoustic parameter with its bathymetric structure. The hypothetical effective angle of a bottom echo θ'/2,corresponding to its normalised length, was the acoustic parameter applied. This parameter broadly characterises the complex acoustic reflecting and scattering properties of the seabed.Its highest values correspond to a layered bottom consisting of soft sediment. The southern Baltic area was classified by a direct comparison of two factors measured acoustically:the statistical distribution of θ'/2, andthe correlated depth structure within selected standardregular geographical areas (15' latitude and 30' longitude) which the total area was divided into.The area size was matched with the density of the measurements collected.The same factors were also estimated for the whole southern Baltic. The study was based on soundings collected on board r/v "Baltica"during regular acoustic surveys in 1995-2003. The classificationapplied provides a new possibility of complex seabed identification and comparison of seabed structure dynamics, useful in benthic research and in the ecologically based administration of marine areas.

The continuous dredging of shipping channels is a commom problem in most estuaries. Shoals constitute navigational hazards, which have to be removed to guarantee a safe access to the adjacent harbors. Dredging is always associated with the dumping of dredge spoil at declared sites, which are normally located close to the dredged channel. In this context, a main problem is the uncertainty, whether the dumped material remains at the site or is further transported by currents and redistributed in the surrounding estuarine area. In the worst case, the previously dredged channel might be re-infilled. However, knowledge about the fate of dumped sediments and their interaction with the existing morphological and sedimentological conditions is still fragmentary, especially in a dynamic tidally influenced environment. The goal of this work is to contribute to a better understanding of the natural dynamic processes and the consequences of dredge spoil dumping in a coastal area. A dumping site situated in the seaward exposed outer Weser Estuary (German Bight) was repeatedly surveyed with a shallow-water multibeam echosounder and an acoustic seabed classification system, which enable to investigate large seabed areas in a cost- and time-efficient mode, and thus the monitoring and investigation of morpho- and sedimentdynamical processes in a high spatial and temporal resolution. The aim of the present thesis was to answer following questions concerning the naturally and artificially changed state of the dumping area: How does the sediment budget change due to the supply of sediment by dredge spoil dumping? What are the predominant sediment transport pathways? How strong is the impact of dumped material on morphological seabed features? How variable is the spatial distribution of sediments in the dumping area?

Acoustic seabed classification with single-beam sounders involves discriminating among bottom types using attributes of their echoes. One attribute that is rich in sediment information is the duration of these echoes, but it needs to be interpreted with care because it depends on water depth, seabed slope and sounder beamwidth, as well as on seabed characteristics. The interpretation relies on an equation for echo duration, which is the sum of four terms: • Spreading time across the seabed from first contact to the periphery of the beam width. • Duration of the transmit pulse. • Time to penetrate into the sediment to a depth from which volume scatter is no longer significant. • Earlier start times due to shorter path lengths if there is macro-roughness such as rocks and macroalgae. Only the first of these depends on depth or slope. This dependence must be compensated to make maps of seabed classes, rather than maps of classes influenced by bathymetry. Working with echoes collected at many transducer altitudes and tilts over homogeneous patches of seabed, this equation is verified. Being able to predict echo durations from a standard seabed (the standard echo length, SEL) allows effective compensation for the depth each echo came from. Seabed slope strongly affects echo durations, shapes, and amplitudes. Provided the slope is not so severe that there is no specular return, the effect of slope on the echo can be compensated in the same manner. Echo durations from rough seabeds can often exceed the SEL through an effect that can be modeled as widening of the transducer beam. In some cases, the difference between SEL and observed echo durations, called the residual echo duration, can be used to determine the seabed sediment without the need for ground truth.

The recent development techniques of acoustic sound survey can provide clearly the inferences of seabed texture, grain size or habitat, seafloor bathymetry and sunken archaeology. Acoustic seabed classification and mapping are possible by using a wide range of acoustic imaging systems. The aim of this study is to get a recent seafloor mapping of the seabed characteristics applying side scan sonar sonography, single beam echo-sounding with QTC seabed classification data, remotely operated under water vehicle (ROV) imageries, and sediment analysis in the study area of the Abu-Quir bay, Alexandria, Egypt. Four types of backscattered patterns were recognized: Pattern of lighter tones corresponds to coarse and medium sediments, Darker tones pattern corresponds fine to very fine sand, tonal patches pattern confined to the transition zone from fine to coarse grained sediment. Moreover Pattern with isolated reflections belongs to archaeological remains and rocky outcrop areas. The seabed sediments of the study area were classified into four types; fine sand, medium sand, very fine sand and silty clay. The isolated reflections pattern has been interpreted as rocky outcrops and archaeological remains of the two ancient Greek cities, Heraklieon and East Canopus. The detection of scattered remains of archaeological structures assumed to be parts of historical blocks, buried archaeological feature. The large flat rocky area may be interpreted as the floors of the submerged cities. The borders of both submerged cities were delimited on the mosaic image where, Heraklieon may covered an area about 600 × 1000 m, while East Canopus may covered 550 × 800 m that situated 1.9 Km at the eastern side from the Abo Qir port.

Abstract Acoustic seabed classification is a useful tool for monitoring marine benthic habitats over broad-scales (>1 km 2 ) and meso-scales (10 m 2 –1 km 2 ). Its utility in this context was evaluated using two approaches: by describing natural changes in the temporal distribution of marine biotopes across the broad-scale (4 km 2 ), and by attempting to detect specific experimentally-induced changes to kelp-dominated biotopes across the meso-scale (100 m 2 ). For the first approach, acoustic backscatter mosaics were constructed using sidescan sonar and multibeam echosounder data collected from Church Bay (Rathlin Island, Northern Ireland) in 1999, 2008 and 2009. The mosaics were manually segmented into acoustic facies, which were ground-truthed using a drop-video camera. Biotopes were classified from the video by multivariate exploratory analysis and cross-tabulated with the acoustic facies, showing a positive correlation. These results were integrated with bathymetric data to map the distribution of seven unique biotopes in Church Bay. Kappa analysis showed the biotope distribution was highly similar between the biotope maps, possibly due to the stability of bedforms shaped by the tidal regime around Rathlin Island. The greatest biotope change in this approach was represented by seasonal and annual changes in the growth of the seagrass, Zostera marina . In the second approach, sidescan sonar data were collected before and after the removal of 100 m 2 of kelp from three sites. Comparison of the data revealed no differences between the high-resolution backscatter imagery. It is concluded that acoustic seabed classification can be used to monitor change over broad- and meso-scales but not necessarily for all biotopes; its success depends on the type of acoustic system employed and the biological characteristics of the target biotope.