Graziela Miot da Silva

Present and Future Challenges of Coastal Erosion in Latin America

ABSTRACT Silva, R.; Martínez, M.L.; Hesp, P.; Catalan, P.; Osorio, A. F.; Martell, R.; Fossati, M.; Miot da Silva, G.; Mariño-Tapia, I.; Pereira, P.; Cienfuegos, R.; Klein, A., and Govaere, G., 2014. Present and future challenges of coastal erosion in Latin America. The coastal zones of Latin America have many landforms and environments, including sedimentary cliffs, deeply incised estuaries, headlands, barrier coasts and low lying, muddy coastal plains. These forms will respond differently to the expected changes in climate and associated sea level rise, which may produce coastal erosion in the future. Considering the coasts of Latin America overall, erosion is not yet a serious threat, although it is widespread and it is severe in some parts. Major erosion problems are frequently associated with human intervention in sediment supply, with poor planning or with the morphodynamic nature of the coast. Permanent erosional processes, locally or regionally, are caused by tectonic subsidence, deforestation and the fragmentation of coastal ecosystems, land use changes and sediment deficits because of infrastructure built along the coast. In this article we analyse coastal erosion in Latin America and the challenges it presents to the region. We first highlight the relevance of Latin America in terms of its biodiversity; then we describe the population at risk, demographic trends and economic growth throughout the low lying coastal zones. We also examine the vulnerability of the region by analyzing the resilience of key coastal ecosystems after exposure to the most frequent hazards that affect coastal zones in Latin America, namely tropical cyclones, sea level rise, ocean acidification, earthquakes and tsunamis. Finally, we discuss seven case studies of coastal erosion across Latin America. We close the study by pinpointing the main areas of concern in Latin America and explore possible strategies to overcome erosion and thus sustain economic growth, minimize population risk and maintain biodiversity.

A review of coastal dunefield evolution in Southeastern Queensland

ABSTRACT Miot da Silva, G. and Shulmeister, J., 2016. A review of coastal dunefield evolution in Southeastern Queensland. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 308–312. Coconut Creek (Florida), ISSN 0749-0208. The Southern Queensland subtropical coastline represents a major depositional system containing 3 of the largest sand islands in the world. The surface of these sand masses comprises foredune ridges and predominantly large transgressive dunefields, deposited episodically during the Quaternary. The chronological sequence of these dunefield phases, however, is still poorly understood. This paper summarizes the information available regarding dunefield transgression events on the southern coast of Queensland and indicates that both marine and climate effects are important controlling factors for dunefield evolution but that an understanding of the relative thresholds of each factor as the main trigger of dune emplacement phases remains a challenge.

Sensitivity of a third generation wave model to wind and boundary condition sources and model physics

Three different packages describing the white capping dissipation process, and the corresponding energy input from wind to wave were used to study the surface wave dynamics in South Atlantic Ocean, close to the Brazilian coast. A host of statistical parameters were computed to evaluate the performance of wave model in terms of simulated bulk wave parameters. Wave measurements from a buoy deployed off Santa Catarina Island, Southern Brazil and data along the tracks of Synthetic Aperture Radars were compared with simulated bulk wave parameters; especially significant wave height, for skill assessment of different packages. It has been shown that using a single parameter representing the performance of source and sink terms in the wave model, or relying on data from only one period of simulations for model validation and skill assessment would be misleading. The model sensitivity to input parameters such as time step and grid size were addressed using multiple datasets. The wind data used for the simulation were obtained from two different sources, and provided the opportunity to evaluate the importance of input data quality. The wind speed extracted from remote sensing satellites was compared to wind datasets used for wave modeling. The simulation results showed that the wind quality and its spatial resolution is highly correlated to the quality of model output. Two different sources of wave information along the open boundaries of the model domain were used for skill assessment of a high resolution wave model for the study area. It has been shown, based on the sensitivity analysis, that the effect of using different boundary conditions would decrease as the distance from the open boundary increases; however, the difference were still noticeable at the buoy location which was located 200-300km away from the model boundaries; but restricted to the narrow band of the low frequency wave spectrum. Uncertainty in wind data and wave boundary conditions were evaluated.Model sensitivity to different formulations of white capping and wind input were examined.Buoy and remote sensing data were used for model skill-assessment.Importance of having several measured dataset in evaluation of model performance is shown.

Wave Energy as a Control on Dune Development on two Regressive Barriers in Southern Brazil

ABSTRACT Dillenburg, S.; Hesp, P.; Cecílio, R., and Miot da Silva, G., 2016. Wave Energy as a Control on Dune Development on two Regressive Barriers in Southern Brazil. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 273–277. Coconut Creek (Florida), ISSN 0749-0208. Two regressive barriers (Cassino and Curumim) were developed during the middle and late Holocene along gentle re-entrants of the Rio Grande do Sul coast, and they have prograded up to 17 km and 5 km, respectively. While Cassino is marked by a surface morphology characterised predominantly by foredune ridges, Curumim displays a surface completely covered by widely spaced ridges, corresponding to phases of transgressive dunefield formation. As wave period and shoreline orientation are very similar for both barriers, and considering that they are subjected to the same deepwater wave climate, the substantial surface morphological differences between the barriers is, at least in part, a direct consequence of variations in wave height at the two sites. In addition, there is a significant difference in potential sand transport and wind power between the two sites. As transgressive dunefields and parabolic dunes can develop as a consequence of foredune destabilization, followed by wind action, it is very possible that at Cassino, during barrier development storm waves were not strong enough to destabilised the foredune system and, in addition, if storm scarping occurred, winds were not competent to destabilise the foredunes, thus providing conditions for the formation predominantly of a foredune ridge plain. Only occasionally, presumably during very strong storms (or multiples thereof), foredune destabilization has resulted in dune transgression. At Curumim, either storm waves and higher wind strengths were more effective in dune destabilization, or foredunes rarely developed allowing the formation of multiple phases of transgressive dunefields during barrier progradation.

Late-Holocene cliff-top blowout activation and evolution in the Cooloola Sand Mass, south-east Queensland, Australia

Cliff-top dunes are a locally important geomorphic features of sedimentary coasts. They are traditionally interpreted as being sourced by (or with) sand derived from the beach below the cliff. This paper presents the results of a stratigraphic and geochronological study of Carlo Sand Blow, a coastal blowout that has developed on top of a high sandy cliff in the Cooloola Sand Mass, south-east Queensland. We use a combination of sedimentological, pedological and geophysical techniques along with optically stimulated luminescence dating to determine the depositional history and evolution of the blowout. We demonstrate that the blowout is dominantly nourished by sand eroded from its floor rather than the adjacent beach. The original dune surface dates to the first half of the last glacial period (c. 40–70 ka) and this dune was deflated in the late-Holocene. Dune activity is directly associated with cliff undercutting because of coastal retreat in the late-Holocene, but coastal erosion on its own is not capable of maintaining aeolian activity. Blowout activity occurred between 2.6 and 2.3 ka and again at 0.3 ka with aeolian sand burying palaeosols. Both soil surfaces contained charcoal and tree stumps in growth position and our study suggests that fire is the immediate trigger for blowout reactivation. It is likely that these fires were anthropogenic in origin, because the site is somewhat protected from natural fire and the ages coincide with intensification of human use of coastal sites in the area.

Steps to improve gender diversity in coastal geoscience and engineering

Robust data are the base of effective gender diversity policy. Evidence shows that gender inequality is still pervasive in science, technology, engineering and mathematics (STEM). Coastal geoscience and engineering (CGE) encompasses professionals working on coastal processes, integrating expertise across physics, geomorphology, engineering, planning and management. The article presents novel results of gender inequality and experiences of gender bias in CGE, and proposes practical steps to address it. It analyses the gender representation in 9 societies, 25 journals, and 10 conferences in CGE and establishes that women represent 30% of the international CGE community, yet there is under-representation in prestige roles such as journal editorial board members (15% women) and conference organisers (18% women). The data show that female underrepresentation is less prominent when the path to prestige roles is clearly outlined and candidates can self-nominate or volunteer instead of the traditional invitation-only pathway. By analysing the views of 314 survey respondents (34% male, 65% female, and 1% ‘‘other’’), we show that 81% perceive the lack of female role models as a key hurdle for gender equity, and a significantly larger proportion of females (47%) felt held back in their careers due to their gender in comparison with males (9%). The lack of women in prestige roles and senior positions contributes to 81% of survey respondents perceiving the lack of female role models in CGE as a key hurdle for gender equality. While it is clear that having more women as role models is important, this is not enough to effect change. Here seven practical steps towards achieving gender equity in CGE are presented: (1) Advocate for more women in prestige roles; (2) Promote high-achieving females; (3) Create awareness of gender bias; (4) Speak up; (5) Get better support for return to work; (6) Redefine success; and, (7) Encourage more women to enter the discipline at a young age. Some of these steps can be successfully implemented immediately (steps 1–4), while others need institutional engagement and represent major societal overhauls. In any case, these seven practical steps require actions that can start immediately.

Changes in vegetation cover on the Younghusband Peninsula transgressive dunefields (Australia) 1949-2017: Changes in vegetation cover on the Younghusband Peninsula dunefields

Studies have shown that the impact of climate change, human and animal actions on coastal vegetation can turn stabilized dunes into active mobile dunes and vice versa. Yet, the driving factors that trigger vegetation changes in coastal dunes are still not fully understood. In the transgressive dunefields of the Younghusband Peninsula (south-east coast of South Australia) historical aerial photographs show an increase in vegetation cover over the last ~70 years. This study attempts to identify the causes of the changes in vegetation cover (1949 to 2017) observed in a typical section of the coastal dune systems of the Peninsula. Vegetation cover was first estimated for various years using the available historical aerial photography (long-term changes – 1949 to 2017) and recent satellite imagery (short-term annual changes – 2010 to 2017) for the area, and then results were discussed against the observed changes in climatic variables and rabbit density, factors that could have played a role in this transformation. Results of longterm changes show that the vegetation cover has increased significantly from 1949 to 2017, from less than 7% vegetation cover to almost 40%, increasing dune stabilization and forming parabolic dune systems. Periods with the largest growth in vegetation cover (1952-1956 and 2009-2013) coincide with a significant decline in rabbit numbers. Rabbit density was found to be the primary factor linked to the rapid vegetation growth and stabilization of the dunefield, for both decadal long-term (last 68 years) and annual shortterm changes (last 8 years). Other factors such as changes in rainfall, aeolian sediment transport, land use practices, and the introduction of invasive plants have apparently played a limited to negligible role in this stabilization process.

Faecal Indicator Bacteria Present in Sand at South Port Beach, South Australia

ABSTRACT Whiley, H.; Austin, J.; da Silva, G.M., and Ross, K., 2018. Faecal indicator bacteria present in sand at South Port Beach, South Australia. Research has demonstrated that bacterial pathogens present in beach sand may be a risk to human health. The indicator species enterococci, total coliforms, and Escherichia coli were measured in beach sand collected from South Port Beach, South Australia, a popular recreational beach. Samples were collected from five distances from the low tide mark (low tide, 10 m, 20 m, 30 m, and 40 m), at three depths (surface, 10 cm down, and 30 cm down), and at five sampling times over a 3-month period. During this time there was a storm that resulted in significant movement of sand from the beach and high flow of the nearby river, and coincided with increased bacterial load. Within a week the bacterial load had returned to previously measured levels. In general, higher bacterial counts were at the surface level compared with 10 and 30 cm below the surface, and the lower counts were at the low tide mark, with increasing distance from the low tide resulting in increasing bacterial loads, and the highest load at the dune edge. This research provides information about the potential health risk of beach sand and a baseline for future studies exploring the microbial risks of Australian beach sand.