Marcelo Rollnic

Variability of Salinity in Pará River Estuary: 2D Analysis with Flexible Mesh Model

ABSTRACT Rosário, R.P., Borba, T.A.C., Santos, A.S., and Rollnic, M., 2016. Variability of Salinity in Pará River Estuary: 2D Analysis with Flexible Mesh Model. 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. 128–132. Coconut Creek (Florida), ISSN 0749-0208. This research aims to study the spatial and temporal variability of the salinity in the Pará River Estuary. The Pará River estuary is among the largest in Brazil, with a mouth of approximately 60 km wide. The Pará River is not a true river because it does not have a spring, but is a hydrographic mesh that receives outflow of several water bodies. There is an ingestion of salt in the Pará River Estuary, different of what occurs within Amazon River, that leads estuarine characteristics onto the continental shelf. The model was implemented based on flexible mesh in the estuarine area of the Amazon River and Pará River basin for one-year simulation. The software D-Flow FM was used to perform hydrodynamic model and, D3D-D-Waq to water quality model. These experiments support a conceptual description of haline dynamics of this system to produce information regarding different scenarios in the region. Fieldworks were made (25h - three points in estuary) in low, high, and transitional rivers discharge in order to evaluate the model performance. The main conclusions are: the numerical modeling showed an upstream saline intrusion about 130 km for the dry period (October to December) and about 70 km for the rainy period (January to May). 2D barotropic condition shows river discharge as the most important force that control the variation of saline intrusion due to the reduction of freshwater flow in the system.

Equilibrium Beach Profile in the Presence of Beachrocks

ABSTRACT Rollnic, M. and Medeiros, C., 2016. Equilibrium Beach Profile in the Presence of Beachrocks 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. 452–456. Coconut Creek (Florida), ISSN 0749-0208. Equilibrium Beach Profile (EBP) models are used to estimate sandy beach profiles, they assume the existence of a shoreface shape that represents an equilibrium condition between wave climate and sediments, making it possible to identify erosion/accretion trends. EBP models suit beaches with near homogeneous grain size sediments. However, in subtropical and tropical areas, beachrocks are often found underlying the beach face, such that EBP models may not be suitable as shadowing areas may favour settling of variable grain size sediments. Our goal was to evaluate the Bruun-Dean EBP model for a beach along which beachrocks were at times absent and at times present as onshore or submerged reefs. Eight 1km-long bathymetric profiles were performed from the surf zone to the 10m isobath and sediment samples obtained at 50, 100, 200, 500 and 1000 m from the surf zone. EBP was computed for distinct coefficient (m) values and evaluated as a function of resulting summed square error. A closure depth of 3.97 m was computed using wave characteristics were derived from 1 year radar records. Along the study area the 3.97 m isobath is positioned 140 to 400m offshore, disregarding the quotas of the beachrocks. At the control areas where beachrocks were absent, m=0.67 yielded the best fit. At areas where beachrocks were present, profiles tended to be steeper and m=0.77 results in a better adjustment near the shore. For the more seaward portion of the profiles, the incorporation of a parameter related to the reef high could improve fitting.

Seasonal Variations of the Amazon River Plume with Focus on the Eastern Sector

ABSTRACT Mascarenhas, A.C.C.; Gomes, G.S.; Lima, A.P.Y.; Silva, H.K.N.; Santana, L.S.; Rosário, R.P., and Rollnic, M., 2016. Seasonal variations of the Amazon River plume with focus on the eastern sector. 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. 532–536. Coconut Creek (Florida), ISSN 0749-0208. The Amazon Continental Shelf (ACS) is a highly dynamic environment as a result of physical processes (tidal, current and wind) and the large river discharge from Amazon and Pará Rivers. This research aims to determine seasonal variations of the plume of the Amazon River in the eastern sector, near the Pará River mouth. Five oceanographic campaigns were conducted on the ACS: April and October 2013; May, July and October 2014. The sampling line followed the shape of the Cabo Maguari (Marajo Island) to 260 km in the shelf break. Nine vertical profiles of conductivity, temperature and pressure and turbidity were collected. It reaches a perpendicular distance up to 200 km from the coast during period of maximum rivers discharge (April and May). During low river discharge (October 2013 and 2014), the plume was restricted to 30 km and presented relative high levels of salinity (20 PSU). The Coastal Water, characterized by high temperatures and low salinity was limited to about - 15 m deep. The Tropical Surface Water, which is considered a high value of salinity and water temperature, was identified in the last sample point to 260 km from the coast in 2014. This water body characteristics is commonly found in the North Brazil Current, then it can be concluded that water mass invades the Amazon continental shelf. Even in low discharge conditions, adjacent ocean water do not invade the the Amazon River mouth, only the Pará River estuary. Because of that, these estuaries present different physical and biological processes.

Runoff and sediment Transport of Portel-Melgaço Water System in an Amazonian estuarine System

ABSTRACT Costa, M. S.; Rolnic, M., P.D., Prestes, Y.O., Rosário, R.P., and Borba, T. A.C., 2016. Runoff and Sediment Transport of Portel-Melgaço Water System in an Amazonian Estuarine System. 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. 18 - 22.CoconutCreek (Florida), ISSN 0749-0208. The Pará River, located in northern Brazil, receives hydrological and sediment contributions from a complex network of basins, such as the Amazon, Portel/Melgaço, and Tocantins river basins. Portel/Melgaço basin, a fluvial-estuarine system situated between the Amazon and Tocantins river basins, is still poorly known. Therefore, the objective of this study is to identify whether there is any hydrological and sediment contribution from Portel/Melgaço river basin to the Pará River. For that purpose, two campaigns were carried out: 1) June, 2013 (transitional season) and 2) March 2014 (wet season). Samplings were carried out over a tidal cycle (13 h) and consisted of a bathymetric surveys; tide measurements; cross sections of streamflows (Acoustic Doppler Current Profiler); and vertical turbidity profiles (Optical Backscatter Sensor) with water sampling (surface and bottom for Suspended Particulate Matter) at three points of the cross section. Our main conclusion is that the inflow from Pará and Amazon Rivers to Portel/Melgaço river basin is higher than the outflow and appears to be highest in the dry season. Thus, the Amazon and Pará Rivers are the main source of suspended sediments to the system, and this characterizes Portel/Melgaço river basin as a retention basin.

Runoff quantification on Amazonian Estuary based on hydrodynamic model.

ABSTRACT Borba, T.A.C., and Rollnic, M., 2016. Runoff quantification on Amazonian Estuary based on hydrodynamic model. 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. 43–47. Coconut Creek (Florida), ISSN 0749-0208. The Amazonian Estuary encompasses a large number of water bodies and four of the 20 largest rivers of the world. It is composed of two conected branches: the Amazon River Estuary and Para River Estuary. This research aims to quantify the net runoff through these branches during wet and dry season based on 2D numerical model. D-Flow Flexible Mesh was used to simulate the hydrodynamics of Amazonian Estuary. The domain encompasses rivers and channels of Amazonian Estuary and floodplain area. The domain covers ≈700 km along the coastline and 145 km offshore. It reaches 716 km upstream through the Amazon River and 430 km through Para/Tocantins River. Curvilinear meshes combined with triangles and 1D channels networks were used during the mesh definition. The net discharge was calculated for one tidal cycle. Five cross-sections were defined to quantify the estuary runoff: four on the Amazon River Estuary and one Para River Estuary. The lateral cross-sections on Amazon River Estuary present net runoff of magnitude of almost 107 m3 for wet season and 106 m3 for dry season, both in downstream direction. The central cross-sections on Amazon River Estuary present runoff of magnitude of 104 and 105 m3 for wet season, both in upstream direction. The cross-section on Para River Estuary presents runoff of magnitude of 106 m3. The Pará River Estuary presents magnitude near to that presented by Amazon River Estuary, making it an important channel of matter transport from continent to ocean.