AIACC REGIONAL STUDY EXPENSE REPORT Project statement of allocation (budget), expenditure and balance (expressed in US$) covering the period: PERIOD 01 JUL 2002 – 31 DEC 2002
Project Number: AIACC_LA26
Principal Investigator(s): VICENTE BARROS
Project Title: “THE IMPACT OF GLOBAL CHANGE ON THE COASTAL AREAS OF THE RIO DE LA PLATA: SEA LEVEL RISE AND METEOROLOGICAL EFFECTS.
Supporting Organizations: Global System for Analysis, Research and Training (START), Third World Academy of Sciences (TWAS) United Nations Environment Programme (UNEP
I hereby certify that all information contained in this expense report is true and correct.
Signed: ____Alberto Boveris______Date: Buenos Aires, 31 de December de 2002
President UBATEC SA
Signed: ____Vicente Barros______Date: Buenos Aires, 31 de December de 2002
CASH ADVANCE INFORMATION AND REQUEST: (All figures should be in US Dollars)
A. Amount of Previous Cash Advances: Date: 04/12/02 Amount: 11.000 u$s
Date: 05/14/02 Amount: 12.620 u$s
Date: 09/11/02 Amount: 30.034 u$s
TOTAL(1): 53.654 u$s
B. Expenditures (by Reporting Period)
Total Expenditures for Period 01 Jan 2002 – 30 Jun 2002: 11400.47 u$s
Total Expenditures for Period 01 Jul 2002 – 31 Dec 2002: 28826.13 u$s
Total Expenditures for Period 01 Jan 2003 – 30 Jun 2003: 0
Total Expenditures for Period 01 Jul 2003 – 31 Dec 2003: 0
Total Expenditures for Period 01 Jan 2004 – 30 Jun 2004: 0
Total Expenditures for Period 01 Jul 2004 – 31 Dec 2004: 0
TOTAL(2): 40226.60 u$s
C. Total Cash-In-Hand: TOTAL(1) minus TOTAL(2): 13427.40 u$s
D. Total Estimated Expenses for Subsequent 8-Month Period: 32825.94 u$s (from expense form)
E. Total Cash Advance Requested (D. minus C.): 19398.54 u$s
INVENTORY OF NON-EXPENDABLE EQUIPMENT PURCHASED AGAINST AIACC PROJECT
Project Number: AIACC_LA 26 Project Title: “THE IMPACT OF GLOBAL CHANGE ON THE COASTAL AREAS OF THE RIO DE LA PLATA: SEA LEVEL RISE AND METEOROLOGICAL EFFECTS. ADMINISTERING INSTITUTION: UBATEC S.A. PRINCIPAL INVESTIGATOR: VICENTE BARROS
Description Serial Nº Date of Original price Present Location Remarks purchase Condition Personal 07/19/02 2020 U$S Good Department Computer: of Physics. Toshiba 5233 University PT: 1100; 256 of La MB; 40 GB; República. multimedia; fax Uruguay 56k.
The physical verification of the items was done by: VICENTE BARROS
Name: Vicente Barros
Signatura:
Date: 13 January, 2003
Total Expenditures for Period 01 Jul 02 - 31 dec 02
Expenses Current Period Expenses of the Estimated Project Budget estimated of the Expenses (01 previous period Cumulative Expenses for Allocation for period June 02 - jul 02 - 31 dec ( 01 jan 02 - 30 Expenses for Subsequent 8- Year February 03 02) jun 02) 2002 Month Period
Object of Expenditure (USD) (USD) (USD) (USD) (USD) (USD)
PERSONNEL 24,250.00 24,758.00 Claudia Herrera 1,943.00 1,524.71 300.35 1,825.06 1,300.00 Julieta Berrenechea 1,571.00 629.48 388.70 1,018.18 610.00 Diego Ríos 1,143.00 861.78 353.35 1,215.13 760.00 Mariano Re 2,186.00 1,506.07 600.70 2,106.77 2,060.00 Gustavo Escobar 1,886.00 1,878.75 1,943.46 3,822.21 0.00 Silvia Romero 486.00 477.71 600.70 1,078.41 0.00 Sebastian Ludueña 0.00 0.00 0.00 0.00 910.00 Moira Doyle 2,200.00 937.68 0.00 937.68 2,610.00 Elvira Gentile* 1,943.00 0.00 0.00 0.00 0.00 Silvia Gonzalez 0.00 1,233.89 0.00 1,233.89 1,300.00 Vicente Barros 2,400.00 1,823.93 0.00 1,823.93 2,400.00 Susana Bischoff 1,200.00 900.00 0.00 900.00 300.00 Angel Menendez 1,800.00 892.68 0.00 892.68 1,800.00 Claudia Natenzon 1,800.00 900.00 0.00 900.00 1,800.00 Jorge Codignotto 1,800.00 892.68 0.00 892.68 1,500.00 Roberto Kokot 1,200.00 892.68 0.00 892.68 900.00 Inés Camilloni 1,200.00 892.68 0.00 892.68 600.00 16,244.72 4,187.26 20,431.98 18,850.00 * Explanation: Elvira Gentile was replaced by Silvia Gonzalez
MATERIALS AND SUPPLIES 500.00 1,700.00 Presented expenses 16.26 0.00 16.26 Presented expenses 22.17 0.00 22.17 Presented expenses 111.43 0.00 111.43 Presented expenses 63.31 0.00 63.31 Presented expenses 310.23 0.00 310.23 Presented expenses 276.81 0.00 276.81 Presented expenses 337.58 0.00 337.58 1,137.79 318.59 1,456.38 1,500.00
EQUIPMENT[2] 1,500.00 2,200.00 Personal Computer 2,200.00 2,020.00 0.00 2,020.00 2,020.00 0.00 2,020.00 0.00
TRAVEL[3] 7,100.00 7,440.00 Vicente Barros 300.00 105.08 453.42 558.50 300.00 Mario Caffera (coordination) 240.00 455.36 146.06 601.42 200.00 Jorge Codignotto (Fiel-work) 900.00 160.00 0.00 160.00 300.00 Claudia Herrera (Field-work) 900.00 0.00 0.00 0.00 0.00 woork) 900.00 0.00 0.00 0.00 300.00 woork) 0.00 37.46 0.00 37.46 300.00 Vicente Barros (Workshop) 400.00 391.63 0.00 391.63 0.00 Susana Bischoff (Workshop) 400.00 402.79 0.00 402.79 0.00 (Workshop) 400.00 402.79 0.00 402.79 0.00 (Workshop) 400.00 371.25 0.00 371.25 0.00 (Workshop) 400.00 0.00 0.00 0.00 0.00 Roberto Kokot (Workshop) 400.00 402.79 0.00 402.79 0.00 Inés Camilloni (Workshop) 400.00 402.79 0.00 402.79 0.00 Walter Vargas (Workshop) 400.00 402.79 0.00 402.79 0.00 Vicente Barros (Course) 500.00 485.95 0.00 485.95 0.00 Susana Bischoff (Course) 500.00 485.95 0.00 485.95 0.00 Mario Bidegain 0.00 0.00 0.00 0.00 200.00 Madelaine Renon ** (coordination) 0.00 0.00 0.00 0.00 500.00 7,440.00 4,506.63 599.48 5,106.11 2,100.00 ** Explanation: Madelaine Renon is a graduate student cooperating with M. Bidegain in Uruguay
CONSULTANTS[4] 10,000.00 2,500.00 D'Onofrio Enrique 3,000.00 0.00 2,650.17 2,650.17 2,000.00 Oscar Andres Frumento 3,000.00 0.00 2,650.17 2,650.17 0.00 Claudia Simionatto 1,500.00 0.00 0.00 0.00 0.00 Mario Nuñez (en conjunto con Claudia Simionatto) 1,500.00 2,500.00 0.00 2,500.00 0.00 Alfonso Pujol 0.00 0.00 0.00 0.00 2,500.00 2,500.00 5,300.34 7,800.34 4,500.00
TELECOMMUNICATIO NS 1,000.00 500.00 78.51 0.00 78.51 300.00
COMPUTER SERVICES 1,000.00 1,000.00 760.48 0.00 760.48 2,000.00
PUBLICATION COSTS (INCL. 0.00 1,000.00 0.00 0.00 Translations 376.64 0.00 376.64 376.64 0.00 376.64 2,500.00
OTHER[6] 0.00 0.00 0.00 0.00 Workshop with 0.00 0.00 0.00 0.00 300.00 300.00
INDIRECT COSTS 1,890.00 1,155.14 UBATEC S.A. (4% Of the received money) 1,201.36 994.80 2,196.16 775.94 1,201.36 994.80 2,196.16 775.94
TOTAL 47,240.00 42,253.14 28,826.13 11,400.47 40,226.60 32,825.94
NOTE: The national currency (pesos) rate of change fluctuates daily.Therefore. The same payment in pesos may have differences in USD. The type of change of the date according to quote of the "Banco Central de la República Argentina"
PROGRESS REPORT
INDEX A) Abstract...... 1
B) Report on the Tasks Scheduled for the July-December 2002 period...... 1 Introduction...... 1 Report on Tasks...... 2 Travel activities...... 27
C) Description of Difficulties Encountered and Lessons Learned...... 27
D) Description of Tasks to be performed in the Next Eight-Month Period...... 28 E) Anticipated Difficulties in the Next Eight-Month Period...... 30 F) Collateral Funds...... 31 G) Connections with the National Communication……………………………32 H) Attached Draft Documents...... 34
A)ABSTRACT
The mean water level of the Rio de la Plata (RP) estuary responds to mean sea level, to the wind field and to the discharge of its tributaries. It was evaluated the ability of the GCMs to reproduce the present features of surface circulation through its sea level pressure field. Models HADCM3, ECHAM4/OPYC3, CSIRO-mk2 and GFDL-R30 represent adequately the mean annual SLP fields and most of their annual cycle. These models were then selected for developing future SLP and low-level circulation regional scenarios.
It was started a GISS with data of the coastal areas of the Argentine coast of the RP. Digitized information was produced on the following items, topography, geology, geomorphology and social vulnerability indicators as well as population. The provisional area of future vulnerability to water floods resulting from climate change is presently occupied by 1, 500 000 people. To study the future behavior of the RP water level is being developed 3 hydrodynamic models that were validated successfully under wind and astronomical forcing.
It was implemented a feedback mechanism with qualified stakeholders to asses the pertinence of the Project objectives to social and governmental demands.
B) Report on the Tasks Scheduled for the July-December 2002 period
Introduction
Task numbers in the work plan were ordered according with the expected end date of the task. The Project has different lines of work converging to a final objective. They must be developed 1 simultaneously in order to arrive to the objective on time. Therefore a possible order to read the tasks of the First and Second Progress Reports following the main lines could be as follows:
Tasks (in bold tasks reported in this document) Climate Scenarios. 1, 2, 13, 27
GISS data on coastal areas . 3, 5, 10, 11, 12, 24, 25
Dynamic and modeling of the Rio de la Plata (RP). 4, 7, 8, 9, 14, 23, 28, 29, 30, 31
Tributaries of the RP. 20, 21
Weather storms. 15,19
Delta advance. 16
Stakeholders 6, 22
Report on Tasks
Task numbers according to the working plan. In brackets the estimated end date reported in the First Report
6. Initial presentation of the project and its objectives through interviews with stakeholders (September 2002)
This activity was accomplished during the period July-November. The project was presented to six key stakeholders. See Annex B4 of the First Report. A brief report of the objectives and methodology of the Project was prepared for this purpose
In addition, the Project was presented to a larger number of stakeholders in the workshop on Social Pertinence of the research developed at the University of Buenos Aires (UBA) in the area of floods. This meeting was part of the process of external evaluation of UBA activities. The Project was invited to participate because it receives collateral funds from the UBA in the framework of a special program. The aim this meeting was to reach a complementary criterion to those of scientific excellence, on the basis of the assessment of the research work in terms of its socioeconomic application.
The modality adopted was to send the documentation on the projects selected to the participants. The meeting took place on Tuesday 8 October 2002. The objective of the Workshop was to evaluate, through a participatory process, the pertinence of the scientific research and its social benefits from the point of view of the stakeholders.
The public institutions and NGOs - Non-Governmental Organizations- that sent representatives to the Workshop were the following: - Department of Water Resources Management, National Secretariat of Water Resources. - Civil Defense Department of Buenos Aires Province. - Secretariat of Environmental Policy and Food Security of the Municipality of Avellaneda.
2 - Sanitation and Hydraulic Works Department, Buenos Aires Province. - GAO (Associated Management of the West) Local Organization. - Pro – Tigre. Non-Governmental Environmental Organization.
There were no objections to the Project objectives and the participants were invited to participate in the Project workshop with stakeholders, next march
8. Development of a large-scale version of the HIDROBID II model (August 2002) This task was reported in the First Report under task 8 and Annex B6. It was considered unfinished because the model validation was no completed. This validation is now reported in task 27.
10. Photo interpretation of dry, normal and flood events (Scale 1: 20 000 and 1: 60 000) (November 2002)
The objective of this task was to contribute to the construction of topographic maps in the Samborobón bay since available altitude information had a resolution of only 2.5-m. According to the IPCC (2001) predicted sea level rise, this value is not enough to precisely define areas that could be affected by future marine ingressions. It was intended to relay only in this task to assess to construct the topography in that region. This was a mistake, because it required of Landsat satellite images of days covering the whole range of tides. Unfortunately, since the available images have an approximately one-month frequency, there are few corresponding to high tides. In addition most of these images were useless because coincided with cloudy skies. Because of this problem, in the First Progress Report there were bestowed some doubts on the successful achievement of this task. This task will now be resumed, but only for small high tides, which are more frequent and therefore can coincide with the image dates. As explained in task 12, this task will complement measures to be taken with a high resolution GPS.
11. Data bases construction in a GIS environment. Point 3 of the Joint Document (October 2002)
This activity continued in two ARC VIEW systems at the Department of Geography and at the Department of Geology. Social, economic, and geological information is being merged with basic cartography and satellite information in the first of these systems. Based on discussions among the different groups, progress is being made on the definition of the nature of data to be included in the database. It was estimated that the construction of the GIS database adapted to the information of Project LA26 would be completed by March 2003, but the inclusion of new data and the use of the system will continue throughout the year 2003.
There was a mini-course on the use of GIS (Geographic Information Systems) to improve the capacities of the personnel involved in GIS use. Lic Sebastián Ludueña lectured the course to the researchers of Project LA 26 at the Geography Institute, UBA. Ms. Silvia González, Mr. Diego Ríos and Ms. Mariana Gasparotto attended this course as well as Mr. Álvaro Ponce, a member of Project LA32. The work was focused on the SIG ARC VIEW The participants were trained in the formulation of databases using information related with the subject of the study (social vulnerability), the utilization and assemblage of satellite images, and the utilization of complementary instruments of the GIS program. 3
Mr. Álvaro Ponce, a biologist and member of the Project LA32 team, made a work sojourn in Buenos Aires from 3 to 6 December 2002. The object of his course was to obtain information and training on conceptual, methodological, and technical aspects of the analysis of social vulnerability, in particular, the use of GIS. Mr. Ponce also worked with Dr. Claudia E. Natenzon in theoretical and methodological aspects of social vulnerability of Project LA32. He was availed of documents, reports and the preliminary reports on the handling of vulnerability. The small relevance of applying a vulnerability index (statistical approximation on a census base) to such a restricted case study as that of the fishermen in the study area of LA 32 was discussed. Suitable geographic scales and data necessary for an assessment of this kind were also discussed.
12. Topographic measurements and fieldwork will be carried out to produce detailed altitude level maps of coastal areas subject to possible floods (November 2002)
Topographic maps of the coastal area and its zone of influence were made using 1:50.000 IGM maps. The shoreline between Punta Rasa (southern limit of the Rio de la Plata) and the Paraná delta was digitized. The area includes the Samborombón Bay and the coastal area between Punta Piedras and San Fernando, which contains highly populated urban centers. The maps show the most important topographic features and 1.25 and/or 2.50-m. contours according to data availability where the geomorphologic conditions of a coastal plain make it impossible to interpolate values without making serious mistakes. The reference coordinate system is Gauss-Krugger, the system used by the Military Geographic Institute. The digital format is DWG with AutoCad references, which will make it possible to be used at a later stage in a Geographic Information System.
Two maps were digitized, one of the Punta Rasa-Punta Piedras section (Fig. 1 of Annex Task 12), which includes the Samborombón Bay, and the other of the Punta Piedras-San Fernando area (Fig 2 of Annex Task 12), which includes the most important urban centers such as Buenos Aires, La Plata, and the Great Buenos Aires cities of San Isidro, Quilmes and Avellaneda.
Not only the coastal areas were mapped but also the inland zones taking mainly into consideration the tributaries of the Rio de la Plata. This will make it possible at a later stage to identify the areas likely to be flooded by marine transgression through the drainage network.
The Samborombón Bay has a low coast populated with lowly towns (General Lavalle and San Clemente del Tuyú). Near the Bay there are cattle breeding areas and highways connecting the region to important tourist centers. It can be said that the area is one of the most vulnerable in Argentina to rise in sea level. Two zones can be distinguished: the high northern area and the southern area practically at sea level. Direct flooding can occur when there is a rise in sea level because the zones are very low. There are two coastal towns in this low area: San Clemente del Tuyú and General Lavalle, which will be seriously affected by a rise in sea level. In the high zones the effect will be an increase in erosion rates causing shoreline retreat.
The area between Punta Piedras and the Parana delta (Fig. 2 of Annex Task 12) shows a low coast touching on a higher one to the north of Matanza-Riachuelo Rivers. This zone corresponds to the most densely populated coastal towns in Argentina, including the City of Buenos Aires, San Isidro, Vicente Lopez, Avellaneda and Quilmes whose low zone will be seriously affected by the rise in sea level. 4
The expected sea level rise in the XXI century will be no more than 1m. Therefore the present topography is not sufficient to analyze the increase of vulnerability of coastal areas. The digitized maps (Fig 1 and 2 of Annex Task 12) will be used as a base for a new map with higher resolution. For this purpose, it will be used field measurements with a GPS system that is being acquired with collateral funds. This system measures altitude with a resolution of 0.05 m. In very low areas of the Samborombón bay where the access is very difficult, satellite images of the area under different tide conditions will be used as a complement.
13. Election of future climate scenarios in cooperation with Project LA32 Point 6 of the joined document (September 2002)
As expressed in the first report, the mean water level of the Rio de la Plata (RP) estuary responds to the wind field and to the discharge of its tributaries. Therefore, the variables required from climate scenarios are surface mean winds over the RP and over the outer adjacent ocean and precipitation over the RP basin. Surface winds are not a standard output of the GCM scenarios. However, this variable is strongly coupled with sea surface pressure (SLP) fields. Consequently, wind scenarios are going to be developed through SLP scenarios.
5
The first step was to evaluate the ability of the GCMs to reproduce the present features of the SLP over a region that encompasses the RP. Therefore, we selected six available SRES-A2 scenarios data in the Modelle and Daten (MOD) web-page of IPCC (www.dkrz.de/ipcc/ddc/html/SRES/SRES_all.html). We also included a comparison with a GCM data provided by the Laboratoire de Meteorologie Dynamique (LMD), France. Table 1 presents a list of the GCMs considered in the analysis and the available period for present climate of their experiments. The observed data considered for the evaluation of the GCMs outputs are the National Centers for Environmental Prediction (NCEP) reanalyses available from the Climate Diagnostics Center web-page (www.cdc.noaa.gov) for sea-level pressure and the University of Delaware rainfall dataset available from climate.geog.udel.edu/~climate/html_pages/precip_ts2.html
model Institution Period HADCM3 Hadley Centre for Climate 1950-2000 Prediction and Research CSIRO-mk2 Australia's Commonwealth 1961-2000 Scientific and Industrial Research Organization ECHAM4/OPYC3 Max Planck Institute für 1990-2000 Meteorologie GFDL-R30 Geophysical Fluid Dynamics 1961-2000 Laboratory NCAR-PCM National Centre for Atmospheric 1981-2000 Research CCCma Canadian Center for Climate 1950-2000 Modeling and Analysis L8-LMD Laboratoire de Meteorologie 1950-2000 Dynamique
Table 1. Global Climate Models (GCMs) considered in the analysis.
Sea level pressure Differences between the monthly and annual mean sea level pressure (SLP) fields over the South American region defined by the latitudes 20°S to 47°S and the longitudes 45W° to 67°W were computed between each GCM data and the NCEP reanalyzes for the different periods available. SLP was selected as indicator to evaluate the goodness of each GCM to reproduce the regional circulation features. The comparison with observed monthly and annual SLP mean fields indicates that only five models (HADCM3, CSIRO-mk2, ECHAM4, GFDL-R30 and L8-LMD) have an acceptable agreement with the observed SLP fields and are able to represent the position of the pressure systems and its annual cycle. In the case of the GFDL-R30 and L8-LMD models, SLP is considerably overestimated all over the region, but their gradients are acceptably represented. Since circulation is related to pressure gradients, the performance of these two models was considered acceptable. Figures 1 to 5 of Annex Task 13 present the SLP difference fields for January, April, July and October for the five models with best performance.
As the Río de la Plata estuary is the focal point of the present study, the GCMs outputs were evaluated in a smaller region presented in Figure 1. Monthly spatial correlation coefficients were 6 calculated between the seven GCMs SLP data listed in Table 1 and the NCEP reanalyzes (Figure 1). Results show that most models have a poor correlation with the observed data during the austral winter months (the only exception is the ECHAM4/OPYC3 model) and high correlation values during the austral summer. Figure 6 also show the poor representation of the SLP fields resulting from the CCCma, L8-LMD and NCAR-PCM models. Consequently, further analysis will be based on the remaining four models.
1.0
0.8
0.6
0.4
HADCM3 0.2 CSIRO CCCMA
correlation coefficient 0.0 NCAR ECHAM4 GFDL -0.2 LMD
-0.4 January March May July September November February April June August October December
Figure 1. Monthly spatial correlation coefficients between SLP GCMs outputs and the NCEP reanalysis
On the annual basis, most models overestimate the annual mean sea-level pressure. Figure 6 of Annex Task 13 presents the annual SLP difference fields with NCEP/NCAR reanalysis for the four models that best agree with the observed data. Though there is some differences in the gradient of SLP, they are small in the RP area and the adjacent ocean.
Conclusion: Models HADCM3, ECHAM4/OPYC3, CSIRO-mk2 and GFDL-R30 represent adequately the mean annual SLP fields and most of their annual cycle. These models are then selected for future SLP and low-level circulation scenarios.
Precipitation Monthly and annual mean precipitation rate differences between each GCM output and the University of Delaware database over the South American region defined by the latitudes 20°S to 47°S and the longitudes 45W° to 67°W were computed in a grid of 0.5º lat. x 0.5ºlon. for 1950-99 period. Comparisons were performed for the four models with best agreement inn the SLP fields: HADCM3, ECHAM4/OPYC3, CSIRO-mk2 and GFDL-R30. Figures 7 to 10 of Annex Task 13 show the differences for January, April, July and October. In all cases, precipitation is largely underestimated in most of the Río de la Plata basin. This error appears in the analysis of the annual mean fields (Figure 11).
Conclusion: The four models have common errors in reproducing the precipitation field over the RP basin. They underestimate the precipitation rate over eastern Argentina, southern Brazil and Uruguay, simulating a precipitation field that is about 50 % or less of the observed one. The best- simulated precipitation field is that of the HADCM3, which in that area simulates an annual rainfall 7 only 75 % of the observed. However, the simulated field for some months only reaches 50 % of the observed values. Other common feature of the four models is that they overestimate precipitation in northwestern Argentina and southern Bolivia.
The fact that the four models have the same error pattern indicates that one or more processes leading to precipitation are not well represented in all of them. One possible cause for this could be the low resolution of the models. Other cause could be a not appropriated convective scheme since in that area most of the rainfall is of convective origin.
Alternatives for precipitation scenarios: The best alternative is to construct high-resolution scenarios. It will be intended to run the PRECIS and the ETA models with high resolution over South America, at least for limited periods of time to asses if the problem with precipitation is caused by the low resolution of the GCM models. Presently, there are daily outputs of HADCM3 and GFDL-R30 available and we expect to get the PRECIS model.
The other possibility is to use the HADCM3 scenarios with some sort of correction accounting for systematic errors. There is some experience for Southern Brazil with Climate prediction model outputs, which indicates that this alternative may work. However, it will remain some doubts because if some basic mechanisms are not well reproduced, systematic errors will not necessarily be the same under new climate conditions. This alternative will be recommended to Projects La 27 and LA 29 until a better solution could be find.
Remaining activities. To complete this task, future regional SLP scenarios from the SRES-A2 outputs of the HADCM3, ECHAM4/OPYC3, CSIRO-mk2 and GFDL-R30 models will be constructed, and then, it will be derived from them the corresponding surface wind scenarios.
Regarding precipitation, as already explained, it will be intended to construct a high-resolution scenario.
REFERENCES Camilloni, I and M. Bidegain: Climate simulation by GCM in southeastern South America. Workshop on Climate Change and the Rio de la Plata. Montevideo 2002.
Kalnay et al., 1996: The NCEP/NCAR Reanalysis 40 years -project. Bull. Amer. Soc. 77: 437-471
14. Training in the hydro-dynamical model HamSOM (August 2002)
During August 2002 Dr. Simionatto and Dr Nuñez (Consultants) worked with Dr Menéndez and collaborators in the use of the HamSOM model for the Project objectives. As it was anticipated in the First Report, there was no certainty that this model could be handed to the personnel of the Project. Therefore two actions were taken. First it was decided to implement a similar model (3 dimensional model) with free code access, the POM model. This activity is reported under task 23. Second, it was required to the consultants to produce with the HamSOM model specific results to help the development of the own models. In addition, the consultants share their experience on the modeling of the South Atlantic and the Rio de la Plata and facilitate processed bathymetric data.
The two questions to answer with the HAMSOM model were: 8 i) How large should be the spatial domain to include satisfactory the water level response to wind forcing? The HamSOM version managed by the consultants is a 3D model which comprises three different scales; a large scale sub model extending along the whole Argentine coast (model A), a medium scale sub model which extension is similar to RPP-3D (model B), and a short scale sub model similar to RP2000 (Simionato 2000, Simionato et al. 2001) (Figure 1 of Annex Task 14). ii) How good is the water level response to the winds produced by weather storms.
To answer these questions, the consultants run 5 experiments with the HamSOM model. Each of them corresponds to weather storms that produced high level on the waters of the RP coasts.
Figure 2 of Annex Task 14 indicates that the answer to the first question is that a domain like the B of figure 1 of the Annex Task 14 is enough.
Figure 2 of Annex Task 14 showing one of the five experiments, also permits estimating of how well the model can reproduce water levels in the Rio de la Plata. Since this is a very elaborated model, its performance indicates the best results that could be expected with a simpler model.
15. Study of weather storms over the region embracing the RP using NCAR/NCEP reanalysis for the period 1950-2000. Study of frequency and strength of these systems and of its seasonal and interannual variability, its trends or decadal variability (August 2002)
Most of this activity and its results were described in the First Report. The analysis of the synoptic situations associated with extreme water levels in Buenos Aires. It was found that the two more frequent modes are not related to weather storms, but to intense anticyclones to the south or west of the RP. These situations are more frequent in summer and in the transition seasons respectively. The third mode, less frequent, is however in the average associated to higher maximum water levels on the Argentine coast. These situations are associated with a low pressure over the north of the Rio de la Plata, a typical situation of cyclogenesis. It was elaborated a manuscript that includes this findings and those reported in the First Report, Annex Task 19.
16. Development of future scenarios for the Paraná delta growth (December 2002)
The objective of this task was to determine the possible advance of the delta front. To this end it was considered necessary to compile historical data from existing maps showing the delta front progression. The methodology of comparing 18th century maps with contemporary ones was complemented with an analysis of aerial photographs and satellite images of the last decades. Modern data (the last 40 years) show that the delta is moving forward approximately 70 m a year.
Evidence of the advance of the Paraná delta. The advance of the delta can be appreciated in at least three aspects:
1) The mouth of the Reconquista River (Fig 1 of Annex Task 16) was practically free from obstacles in 1731, it was partially obstructed by small islands in 1802 and 1829, and it was totally blocked in 890, i.e. there was no direct communication between the Reconquista and the Parana de las Palmas rivers. 9
2) The mouth of the Lujan river underwent a similar process: it was free from obstacles in the 1731, 1756 and 1783 maps but not in 1731 sketch and in the 1762 and 1784 maps. There is certain confusion about the situation in the 18th century although we have accepted the data of the sketch because it was made by a resident of the zone or a person directly familiar with it. It can nevertheless be clearly seen, on the analysis of the more recent maps that the old mouth to the north of the Luján river in the Paraná de las Palmas river was further away from the distal part of the delta
Therefore, in the 1731 sketch, the Luján River and the Reconquista River flow into the Paraná de las Palmas. In later maps (end of 19th century) both the Lujan and the Reconquista rivers flow into the Río de la Plata because of the continuous accumulation of sediments. Finally, at the beginning of the 20th century, only the Luján River flows into the Río de la Plata and the Reconquista flows into the Luján.
3) In the 17th century maps, few islands can be observed in the delta while in later maps their number increases.
With the data obtained to date it is possible to say the delta advance has slowed down since 1950 to date as compared to the 1890 – 1950 period as can be seen in Figure 2 of Annex Task 16. Future evolution during the XXI century will depend on the impact on the Rio de la Plata estuary of Climate Change- Therefore, this task will continue when the Rio de la Plata´s scenarios will be developed.
17. Joint Course on Climate Change with Project L32 as explained in Point 11 of the joint document (September 2002)
An intensive course on Climate variability and anthropic influences was lectured at the University of la República (UdelaR) in Montevideo during October 2002 as a joint activity of Projects LA 32 and LA 26. From Project La26 participated V. Barros and S. Bischoff. The course was part of the Master of Science program on Environmental Sciences of the UdelaR and it was basically similar to a regular course offered at the Master of Science Program on Environmental Sciences of the University of Buenos Aires. However the course was adapted to include aspects of vulnerability and adaptation as well as matters of Uruguay. More details and the topics of the course are in Annex Task 17.
18. Joint workshop with Project L32 as explained in point 10 of the joint document (September 2002)
The workshop was held in Montevideo in September 25-27, 2002. It included general presentations from both Projects and individual presentations as well discussions on common subjects. The participants of our Project were V. Barros, S. Bischoff, A. Menendez, C. Natenzon, R. Kokot, I. Camilloni, W. Vargas, M. Re and G. Escobar. The last two were funded with the collateral funds of the University of Buenos Aires Project. All the participants made presentations. The proceedings of the Workshp will be reported by Project LA 32.
10 19. Writing of a paper manuscript on the study of weather storms over the region embracing the Rio de la Plata using NCAR/NCEP reanalysis for the period 1950-2000 (October 2002)
A manuscript on this subject entitled: ¨ Surface level atmospheric conditions associated to extreme surge tides in the Rio de la Plata estuary ¨ was prepared by Gustavo Escobar, Walter M. Vargas and Susana A. Bischoff . It is being submitted to the International Journal of Climatology. Copy of the manuscript is in Annex Task 19.
20. Estimate of extreme streamflow events. Statistical approach based on historical data and a conceptual approach based on the relationship of rainfall and discharge with SST in the sub-basins of the Paraná and Uruguay rivers. Point 1 of the Joint Document (November 2002) . Paraná River The greatest monthly discharge anomalies of the Upper Paraná of the 1904-1998 period were examined with focus on the contribution from the sub-basins and the climate forcing of these events. The major discharge anomalies in Corrientes originated in the central Upper Paraná basin. The contributions from the Paraguay and the northern Upper Paraná rivers to these anomalies were relatively small. About two thirds of the major discharge anomalies in Corrientes occurred during El Niño events, and none of these major anomalies took place during La Niña events. The major discharge anomalies that were related to El Niño occurred either in the spring of the year of El Niño onset or in the autumn of the following year (autumn (+)) accompanying the precipitation signal of El Niño in eastern subtropical South America. The top discharges of the Paraná River at Corrientes occurred in the autumn (+) whenever El Niño SST anomaly in El Niño 3 region persisted until this season. The remaining third of the major discharge that were not related to El Niño, took place during the austral spring or the austral summer of neutral periods. In each season, they share a common SST anomaly pattern in the proximity of the South American coasts.( Paper in Annex Task 21)
Uruguay River A manuscript is being written with the results described in July in the First Report. There are three main conclusions. First: The greatest peak discharges are modulated by synoptic storms, not lasting more than a few days Second: the greatest peak discharges were associated to rainfalls that follows some days of strong warm and humid low- level flow from the northwest over the basin Third: At seasonal scale, discharges are greatly modulated by the ENSO phases, even more than in the Paraná River, with almost all the greatest discharges during the El Niño phase.
It is now required the future precipitation scenarios to estimate the future discharges
21. Writing of a paper manuscript on extreme streamflow events in the Paraná and Uruguay rivers (December 2002)
11
The manuscript ¨ The greatest discharge events in the Paraná River and their climate forcing¨ by Inés Camilloni and Vicente Barros was submitted to the Journal of. Hydrology. Copy in Annex Task 21
22. Consultation about demands and communication of Project partial results with stakeholders through mail and email (December 2002)
- Characterization of social and institutional stakeholders associated to Project LA26. A summary of characterization of social-institutional stakeholders associated to the Project, as informed in the first progress report, is presented in Annex B4 of the First Report. The outstanding features and background information that have been considered relevant in the selection of each stakeholder for inclusion in the consultation process were shown in that Annex.
- Inter-consultation with social stakeholders. Questionnaire and preliminary results Inter-consultation with social stakeholders associated with the project was based on the following questions:
1. What are the general links between the aims of the project and the aims of your own projects or activities? 2. Which aspects of the project do you consider to be unclear, or are unknown to you? 3. On which subjects or aspects of the project would you like to receive additional technical information? 4. What is your opinion on the methodologies to be used in the project? 5. What information or product of the project do you consider to be directly applicable for the activities of your institution? 6. What information or product of the project do you consider not to be directly useful, yet of interest or applicable in future activities? 7. Do you consider that the information and the products of the project may be useful or of interest for any other institution, group, etc., with which your institution interacts? If so, which and in what way? 8. Would you add any objectives to the project? 9. Would you add or modify the products to be obtained? 10. Do you identify any particular aspects in which you/your institution could make contributions to the project? If so, which? What specific contributions? 11. Upon analysis of the project, its objectives and products, can you think of any future activities or exchange between your institution and the research team of the project? 12. Could you suggest consultation with any other key persons from your institution who could provide information? If so, please provide references. 13. Provide guidelines on methodology and frequency of consultations. 14. Provide information on the institution - profile - activities. Recommended sources.
Four of the six associated stakeholders consulted have sent replies: City Foundation, Federal Emergency System (SIFEM), Redes and the Defendant of the People of Buenos Aires. A summary of each reply is given below.
Summary of reply from City Foundation This Foundation shares the aim of elaborating reliable and scientifically rigorous information that will allow responsible planning and management of coastal areas. 12
The Foundation requests: To receive information on the coastal fringe of the urban area of Buenos Aires, diagnoses and projections on the pattern of floods.
Remarks Concerning the proposed methodology, the Foundation suggests, based on its own experience, that emphasis be placed on consultation with local inhabitants, who know the problem though their own, direct experience. The Foundation thinks it would be useful to predict changes in coastal fringe patterns in the short term. It also suggests that the authorities, investors and the local community need to know about these changes before decisions are made. They state that there are organizations along the coastal fringe that are concerned about these problems, but sometimes have limited access to information and decision-making instances.
Contributions of City Foundation to Project LA26 They suggest incorporating in the Project communication of results (during and after the process) to those concerned. Should the project wish to widen the scope of the consultation process with the community, they are willing to provide contacts with groups, organizations, etc.
Summary of reply from SIFEM The main interest expressed by this organization is the sharing of information for the elaboration of risk maps. The products of the project will allow validation of data from the La Plata Basin: discharge regimes, especially in the Paraná Delta front.
They request: To receive information on climatic, geologic and hydraulic variables.
Remarks: All the products of the project, as well as its applications, are useful for the aims of SIFEM, for its base organisms, and for the provincial organisms related to emergency management. They do not suggest any additional aims or products to be obtained from the Project.
Contributions of SIFEM to Project LA26: To make all the information compiled by SIFEM available to the project, to be integrated through GIS databases.
Summary of reply from REDES The aim of REDES is the participation of the civil society in matters of science and technology. For this reason, they are particularly interested in a further development of the inter-consultation component.
They request: They would be interested in receiving information about means of evaluating results of the inter- consultation process.
Remarks
13 They believe that the design, implementation, and results of the inter-consultation process are useful to them. They do not suggest any additions to the objectives or products to be obtained from the Project.
Contributions of REDES to Project LA26 They inform that an Ibero-American Network of groups devoted to research on and management of participation of the civil society, and democratization of science and technology, is currently being built. This network is a potential receptor of products and results of the Project.
Summary of reply from the Defendant of the People of Buenos Aires The Defendant organized a Seminar-Workshop on “Adaptation of Buenos Aires City and its Urban Area to Climate Change” in November 2001. Proposals from the meeting that have a more direct bearing to project LA26 are the following: - To implement a rain measuring network in those watersheds affecting the Buenos Aires suburban area, as an essential part of a system to forecast water level peaks and issue flood warnings that include estimates of rain intensity through remote sensing. - To elaborate a program of environmental indicators of sustainability related to climate change. - To implement legislation, regulations and recommendations for construction systems and selection of materials and products to be used in construction of houses in areas identified as subject to flooding.
The Defendant of the People requests: They suggest that the study on influence of the rise of ground water levels in the whole area be taken into account when analyzing coastal flooding.
Remarks They consider the work methodology proposed in LA26 to be correct. They would not modify the products to be obtained, or include any new ones. They consider that the information that will emerge from LA26 is highly useful for government institutions of diverse areas, such as urban planning, environment, social development, social emergencies and civil defense.
Contributions of the Defendant of the People to Project LA26 They have not been able to identify any aspect of the project in which they could contribute.
REFERENCES De Marchi, Bruna and Silvio Funtowicz (1994) General guidelines for content of information to the public. Directive 82/501/EEC- Anex VII. Community Documentation Center on Industrial Risk. JRCEC, EUR 15946 EN. Hemmati, M. (2002) Principles of stakeholder participation and partnership. Mimeo. Natenzon, Claudia E. y Héctor A. Poggiese (2002) “Collaborative planning and co-management: The development plan for Zudañez, Chuquisaca, Bolivia”. En: Implementing sustainable development: integrated assessment and participatory decision-making processes. H. Abaza, A. Baranzini, editors. Great Britain,UNEP/ Edward Elgar (141-154). ISBN 1 84064 913 5
23. Implementation of the hydrodynamical models (November 2002)
Description of the main characteristics of the hydrodynamics of the Río de la Plata (RP) and the Continental Shelf has been presented in several papers (Framiñán et al. 1999, Campos et al. 1999,
14 Piola et al. 2000, Menéndez 2001).In this Project, numerical simulation of the flow dynamics is being performed with three hydrodynamic models, namely:
i) RP2000: It is a high-resolution (1 km x 1 km) 2D-Horizontal model of the Río de la Plata, extending from its head down to its mouth (Figure 1 of Annex Task 23), implemented at the National Water Institute (Jaime & Menéndez 1999). It is based on software HIDROBID II, developed by Menéndez (1990). ii) RPP-2D: It is a lower-resolution (2.5 km x 2.5 km) 2D-Horizontal model which, in addition to the Río de la Plata, includes an extended area of its maritime front that goes beyond the Continental Shelf (Figure 2 of Annex Task 23). It is also based on software HIDROBID II (Menéndez 1990). iii) RPP-3D: It is a 3D model, which extends over the same domain as the previous one. It is based on software POM (Blumberg & Mellor 1987, Mellor 1998).
The objective of RP2000 is to reproduce the hydrodynamics of the Río de la Plata with high resolution, taking as boundary conditions results provided by the larger-scale models. The model is able to represent adequately the water levels. The calculated depth-averaged velocities are also representative, except at the outer river, where, due to the 2D nature of the model, density stratification (due to salinity intrusion) cannot be taken into account.
Model RPP-2D is designed to include fetch distances, long enough to build up the storm surges which penetrate through the river mouth. It has the same possibilities and limitations as RP2000. It provides the boundary conditions for the latter one at the river mouth.
The objective of model RPP-3D is to study the dynamics of stratification along the outer Río de la Plata. Its 3D nature allows it to reproduce such dynamics.
Finally, HANSOM-CIMA model was used as a reference model in order to provide results to compare the present developments. It is based on software HAMSOM (Backhaus 1983, 1985).
IMPLEMENTATION OF MODEL RPP-2D In the previous Report, the implementation of model RPP-2D was presented. As an illustration, in figures 3 and 4, of Annex Task 23 instantaneous water level contour lines and velocity fields for two different stages are shown. Validation of this model is reported as task 27.
IMPLEMENTATION OF MODEL RPP-3D Prior to implementation of model RPP-3D, some work had to be done in order to prepare the original code POM, as downloaded from the Web. This consisted in writing subroutines for bathymetric data reading, grid and mask generation, implementation and reading of boundary conditions, parameterization of resistive effects and preparation of output for post-processing.
As a first step in getting acquainted with POM and, in addition, in interpreting the main phenomena to be simulated, a series of runs were made on a simplified problem of similar dimensions to the present one: a prismatic channel with a wave entering through its southern border.
15 A 50 m deep horizontal bottom was initially considered, but a lateral step was later introduced where the water depth jumps abruptly to 1000 m. A non-reflecting boundary conditions was imposed at the northern border. The incoming wave was taken as sinusoidal, with 12 hours period and 1.5 m amplitude around a mean water level of 0.80 m. In the following table, the five cases are described:
Case Geometry Incoming wave Coriolis A Without step Uniform Yes B With step Uniform No C With step Uniform Yes D With step Decreasing exponentially Yes Uniform on platform, null E With step Yes on deep zone
After this experience, preliminary runs were made for the Río de la Plata and its maritime front, using forcing data available from model RPP-2D. Figures 6 and 7 show plan view of water levels and the velocity field for two instants of time.
REFERENCES Backhaus, J.O., 1983, A semi-implicit scheme for the shallow water equations for application to shelf sea modelling, Continental Shelf Research, 2(4), 243-254. Blumberg, A.F., Mellor, G.L., 1987, A description of a three-dimensional coastal ocean circulation model, in Tree-Dimensional Coastal Ocean Models, Vol. 4, edited by N. Heaps, pp. 208, American Geophysical Union, Washington, D.C.. Campos, J.D., Lentini, C.A., Miller, J.L., Piola, A.R., 1999, Interanual variability of the sea surface temperature in the South Brazilian Bight, Geophysical Research Letters, 26(14), 2061- 2064. Destuynder, V., 2002, Modelación Hidrodinámica Tridimensional del Río de la Plata, Report LHA-INA 214-01-02. Framiñán, M.B., Etala, M.P., Acha, E.M., Guerrero, R.A., Lasta, C.A., Brown, O., 1999, Physical characteristics and proceses of the Río de la Plata estuary, In: Perillo, G.M., Piccolo, M.C., Pino, M. (Eds), Estuaries of South America. Their geomorfology and dynamics, Springer- Verlag, Berlin, pp. 161-194. Jaime, P., Menéndez, A.N., 1999, Modelo hidrodinámico Río de la Plata 2000, Report LHA-INA 183-01-99, INA, Argentina, September. Mellor, G., 1998, User Guide for A Three Dimensional, Primitive Equation, Numerical Ocean Model, Princeton University, 1-43. Menéndez, A. N., 1990, Sistema HIDROBID II para simular corrientes en cuencos, Revista internacional de métodos numéricos para cálculo y diseño en ingeniería, Vol. 6, 1. Menéndez, A.N., 2001, Description and modeling of the hydrosedimentologic mechanisms in the Rio de la Plata River, VII International Seminar on Recent Advances in Fluid Mechanics, Physics of Fluids and Associated Complex Systems, Buenos Aires, Argentina, October. Piola, A.R., Campos, E.J., Möller, O.O., Charo, M., Martinez, C., 2000, Subtropical Shelf Front off eastern South America, Journal of Geophysical Research, 105(C3), 6565-6578. Servicio de Hidrografía Naval (SHN), Tablas de Marea 1997, Argentina.
16 Simionato, C., 2000, Oceanographic Investigations of the Argentinean Continental Shelf and the Rio de la Plata, Report CIMA/CONICET-UBA, Argentina. Simionato, C., Nuñez, M.N., Engel, M., 2001, The Salinity Front of the Río de la Plata – a numerical case study for winter and summer conditions, Geophysical Research Letters, 28(13), 2641-2644.
24. Geomorphology description and study of the evolution of the coastal area and construction of geomorphology maps (February 2003)
It was found necessary to made a geological description, necessary to assess the endurance of the coastal areas to the aggression of the sea
Geology A geological map was made of the coastal area of Samborombón Bay (Fig. 1 of Annex Task 24), which includes the digitization of the different units and their lithological features represented in the same format as the topographic maps.
The variable lithology identifies the type of rock or sediment present in the coastal area. The dates were obtained from surveys made for this project and previous studies: Tricart (1973), Fidalgo et al. (1975), Parker et al. (1990), Codignotto and Aguirre (1993) and Kokot (1999). In the Samborombón Bay zone we can separate two areas identified in Fig 1 of Annex Task 24, which shows the old shoreline, geologically represented by Pleistocene sandstone outcrops. The outcrops in the Punta Piedras area consist of Pleistocene sandstone firmly cemented with calcium carbonate, which in general have different formational names. In the lower zones corresponding to lakes or close to the rivers there are sediments of silts and lower proportion of sands adjudicated to the Lujan and La Plata formations. There are tuff gravel insertions. There are aeolian deposits over these of sandy and clayey silts and silty sands.
The coast is formed by tidal flat clayey sediments and a line of cheniers where the crab swamps are located. In the continental area, beyond the present shoreline, there are Holocene beach ridges and barrier islands formed by sand with abundant sea mollusks. Spalletti et al. (1987) studied the sedimentology and Codignotto and Aguirre (1993) and Aguirre (1996) describe the geomorphology, genesis and fauna associated to these deposits.
Between Punta Rasa and Punta Médanos (located to the south of the area under study) the outcrops correspond to dune and Holocene beach ridge deposits of fine and medium sands with bivalve fauna and gastropoda partly cemented with calcium carbonate. The area was formed during Holocene transgression (Dangavs 1983) and started growing from the cape to the south of Punta Mogotes (Violante 1988) where the deposits were studied by Teruggi 1949). Tidal flat deposits are formed of clay, silt and fine sand. Alluvial, generally sandy deposits are found in the valleys of the principal rivers. Beach ridge deposits corresponding to barrier spits which form the present shoreline between Punta Rasa and the south of Punta Médanos are formed of sands with mollusk fossil remains. (Codignotto and Aguirre, 1993 and Kokot, 1995, 1997).
Coastal outcrops, represented by unconsolidated sediments and rock show the resistance to coastal erosion in relation to the attack force of wave energy. These outcrops indicate that the Punta Piedras area, formed by consolidated rocks, offers greater resistance to erosion than the rest of Samborombón bay, which is composed of unconsolidated sediments.
17 Geomorphology A geomorphologic map (Fig.2 of Annex Task 24) was made based on the digitalization of the different geomorphic units. The geomorphology of the area was interpreted using the Landsat 5TM 224/085 30m- resolution satellite image of March 3 1998 provided by the National Commission for Space Research. SHN aerial photographs. Scale 1-40,000 and field tasks.
The use of satellite images and the digital treatment combining bands and applying filters made it possible to differentiate the areas of interest and separate the units which stand out in the image because of the unequal presence of water and vegetation. This was particularly useful in the tidal flat area where different units were separated.
FLUVIAL LANDSCAPE The northern area is higher and the landscape was formed by fluvial action and constitutes are flat area furrowed by rivers which drain in part in the Samborombón Bay and in part towards the coastal area north of Punta Piedras. This area is separated from the Samborombón Bay zone by a small cliff in a zone formed by tidal flats classified as follows: Risen tidal flat: this is not subject to current sea action and was formed during the Holocene sea transgression some 6,000 years BP (Codignotto and Aguirre, 1993). Little organized drainage is identified on this surface due to the small slope of the area but it becomes organized following the route controlled by the old tidal channels Extraordinary tidal flat: this is an area, which is flooded during extraordinary and/or meteorological tides. When changes in sea level occur caused by storms, a band some 2 km wide that in normally is higher than high tide is submerged. In this way a sublitoral environment is formed which is constituted by a high crab site (Tricart 1973) where there is series of ponds which are flooded during these episodic elevations during storms. These ponds are not in general connected by tidal channels and the water level drops slowly by evaporation. On this beach the waves are not very effective due to the resistance produced by contact with the bottom, which is practically flat. Nevertheless, all along the beach a certain erosive effect can be observed carrying fine suspended material. Semidiurnal tidal flats: this is a coastal strip, which is exposed by the cycle of semidiurnal tides. This is a surface slightly sloping to the sea and furrowed by well-developed tidal channels between General Lavalle (Fig. 3 of Annex Task 24) and San Clemente del Tuyú. Near the latter, its direction is controlled by the presence of beach ridges. Cheniers: This is a ridge shaped morphological zone with little relief located in the central area of the Samborombón Bay. Beach ridges: these are present in the north center of the Samborombón Bay and in the southern part forming Punta Rasa and a spit which lies between Punta Médanos and Punta Rasa. Codignotto and Aguirre (1993) explain the genesis of the area. Kokot (1997) studies the beach ridge deposits and explains the acting beach dynamics. Dunes: This is the zone of coastal dunes on the eastern coast of the Punta Médanos-Punta Rasa area. Alluvial plain: The most important are the ones of the Salado and Samborombón rivers located in the northern part of Samborombón Bay. This landform can also appear at the mouths of some of the minor streams near to the General Lavalle zone.
SALADO RIVER BASIN The Salado River flows into the Rio de la Plata in the Samborombón Bay after crossing approximately 650 km from its sources at an altitude of 100 m above sea level (CFI 1962). The Salado River system includes the Samborombón River and the Vallimanca and Las Flores 18 streams where the slope is 0.1 – 0.3 m/km and the area is 94,000km2. The lower stretch runs 98 km with a slope of 0.013 from the La Tigra pond to Samborombón bay. Channels 9, 11 and 12 drain the low basin. Streams A, 10 and 18 drain low, adjacent areas and channel 15 relieves the Salado River. The channels collect the waters of the high basins taking them to an area of embankments for their discharge, avoiding the flooding of fields in the low basin.
Geomorphologic Evolution The area of influence corresponding to the Rio de la Plata has a complex hydrodynamic, thus creating many landforms. The present coastal forms have developed on a Pleistocene erosive platform. During the last Pleistocene transgression the sea covered the NE part of the province of Buenos Aires, Argentina. This level reached about 10 m of the present sea level (Fig. 4A of Annex Task 24). Later a regression and another transgression made the formation of a group of barrier islands possible between P. Piedras and Conesa (Fig. 4B of Annex Task 24). This formation started approximately 7,000 years BP with a level of 5m over the present sea level. This process ended some 3,500 years ago.
At present the coastal area between Mar del Plata and Punta Piedras presents erosion of different intensity according to which stretches of the coast are considered. (Codignotto, 1996). Due to the effect of the waves coming from the southeast, concentrated erosion started at a point located in Villa Gessell (Fig.4B of Annex Task 24). This causes on one hand beach ridges which moved to the south and created the Mar Chiquita pond and on the other generated a big barrier spit in the north (Fig.4C of Annex Task 24). Finally, a small regression and progradation occurred to the present sea level. The relict forms of both barriers are 2.5 to 5 m above the present sea level (Fig. 4D of Annex Task 24). Today, the sector between Mar del Plata and Punta Médanos presents marked erosion. The only sector of natural accretion in the north between Punta Médanos and Punta Rasa shows indices of anthropic erosion.
Samborombón bay has very varied geomorphological characteristics along its coast. Within the Samborombón Bay, represented basically by elevated tidal flats (1.80 – 0.25 m above sea level) and the present tidal flat, clear indices of incipient erosion can be observed. The northern area, Punta Piedras, has a small cliff, which prevents direct flooding. The rest of Samborombón bay, however, constitutes a low area where transgression occurs through river courses and existing tidal channels. Different landforms offer a different resistance to erosion, such as the beach ridges compared to tidal flats and channels.
REFERENCES Aguirre, M.L., 1996. Cambios ambientales y climáticos en la región costera bonaerense durante el Cuaternario tardío. Evidencias malacológicas. IV Jornadas Geológicas y Geofísicas Bonaerenses. Junín: 35-45. CFI, 1962. Recursos Hidráulicos Superficiales Vol. I, 1962. CFI. Tomo IV. Codignotto, J.O. 1996. Cuaternario y Dinámica Marina. XIII Argentine Geological Congress. V. A. Ramos y M. A. Turic, 17-28. Codignotto, J.O. and Aguirre, M.L., 1993. Coastal evolution, changes in sea level and molluscan fauna in northeastern Argentina during the Late Quaternary. Marine Geology, (110): 163-175. Dangavs, N.V.,1983. Geología del complejo lagunar Salada Grande de General Lavalle y General Madariaga, provincia de Buenos Aires. RAGA, 38(2): 161-174. Fidalgo, F., F. De Francesco y R. Pascual, 1975. Geología superficial de la Llanura Bonaerense. VI Argentine Geological Congress. Bahía Blanca. pag. 103-138. Kokot, R.R., 1997. Littoral drift, Evolution and Management in Punta Médanos, Argentina. Journal 19 of Coastal Research, 13(1):192-197. Kokot, 1999. Cambio Climático y evolución costera en Argentina. Doctoral Thesis FCEyN (UBA) 329 pp,.
25. Develop of a Social Vulnerability Index to flooding in a GIS environment. Point 3 of the Joint Document (February 2003)
- Delimitation of study area In order to develop a social vulnerability index and its expression in a GIS context, it was necessary, as a first step, to delimit the geographic area of study. Criteria were established to delimit the area that could be affected by a rise in average sea level as a result of climate change and hence to define the political-administrative units involved.
The first delimitation of the study area was carried out through the identification of the area directly affected by floods, considering the political-administrative units involved based on two criteria: a) that they be located on the coastal area of the La Plata river; b) that they include the area comprised between 5 m above average sea level and the coastline. The 5 meter mark is a first estimate, based on assumption of a maximum scenario of sea-level rise in the year 2100 (1 m for the neighboring region in the South Atlantic) and the maximum tidal peak registered (4.05 m). These figures are provisional and will be adjusted as indicated in results of studies currently underway under other Project tasks.
It should be noted that the application of an exclusively physical-natural criterion in the delimitation of the study area is not an exclusive or excluding condition for the characterization of social vulnerability, for the following reasons: i) When the littoral area is affected, the rest of the territory that is part of the political- administrative units involved will also suffer the socioeconomic effects of the phenomenon. Political decisions that may be proposed and eventually made on the potentially affected area are largely circumscribed to the political-administrative units involved. ii) The socioeconomic and demographic information compiled from the National Censuses of Population and Housing (CNPyV), necessary for the characterization of social vulnerability is consolidated in political-administrative units (Municipalities/Districts) and sometimes in smaller units (census fractions and radii).
Since the 5-meter-above-sea-level contour line comprises a number of political-administrative units that include those located in the coastal area of the Plata River, we decided to consider all political- administrative units that contain within their boundaries all areas below 5 m above sea level potentially liable to be affected. Therefore low areas bordering the Reconquista River in San Fernando County, and low areas in the floodplain of the Matanza-Riachuelo basin, located within Buenos Aires city (for example, neighborhoods such as Villa Soldati and Nueva Pompeya) were included. The low areas of the continental sector of Tigre County located between the urban sector and the locality of Dique Luján, which clearly illustrate the growth of closed urban polderized complexes, were also included.
- Available demographic information Information on the so-called “primary context” or “directly affected” area (counties of Buenos Aires Province plus Buenos Aires City), including information on demography from the National Censuses of 1991 and 2001, is presented in Table 1 of Annex Task 25.
20 - Polygon of census fractions and radii Given that census fractions generally coincide with the county districts, the next task was to identify the polygon of districts comprising the area in the Buenos Aires counties that will be directly affected.
Using the different possibilities provided by the GIS computerized program - ArcView 3.1, different views of the area were superimposed. These views are associated with two different types of information: The 5-meter contour line. The political-administrative units and their corresponding census fractions and radii, according to the 1991 National Census of Population and Housing (CNPyV), carried out by the National Institute for Statistics and Censuses (INDEC). Once this superposition had been completed, and with the aid of satellite images and topographical maps on a 1:50,000 scale published by the IGM (Military Geographic Institute), it was possible to obtain a delimitation of the study area. This area includes political-administrative units located between Tigre County (Buenos Aires Province) in the Northwest and General Lavalle County (Buenos Aires Province) in the Southeast, and also Buenos Aires City.
Based on this delimitation, a table showing the fractions and radii of the political-administrative units included in the study area was drawn up. Given the large territorial dimensions and the great number of census radii present in some sectors (Buenos Aires Metropolitan Area [BAMA] and La Plata City), the study area was divided in two in order to obtain a clearer graphic representation. Map 1 of Annex Task 25 shows the political-administrative units of the BAMA sector. Map 2 of Annex Task 25 shows the distribution of the census fractions with respect to the 5-meter contour line of Buenos Aires City.
The following criteria were used to define the polygon: Any census radii and fractions crossed by the 5-meter contour line is incorporated in the study area. An exception is made when the areas concerned present no population; in such case, they are not considered part of the study area.
In addition, the population data for the census radii pertaining to the BAMA political- administrative units were systematized and the total population corresponding to these units was identified. As an example of this task, Table 2 of Annex Task 25 shows the results for one of the administrative units analyzed. Table 1 summarizes the results of this task for all the administrative units considered.
TABLE 1 – TOTAL POPULATION OF STUDY AREA. BAMA SECTOR
Political-Administrative Units Population in affected area (inhab. – NPC 1991) Tigre 142,500 San Miguel 6,146 Hurlingham 2,850 Tres de Febrero 25,235 San Martín 46,824 San Fernando 95,151 San Isidro 30,553 21 Vicente López 8,967 Capital Federal 343,199 La Matanza 43,843 Ezeiza 3,348 Esteban Echeverría 20,003 Lomas de Zamora 176,889 Lanús 159,845 Avellaneda 274,121 Quilmes 68,146 Berazategui 22,171 TOTAL FOR BAMA 1,469,791
Upon analysis of Table 1, it may be inferred that even taking into account only these political- administrative units of the BAMA, the potentially affected population is of about one million and a half inhabitants. Buenos Aires City and suburban counties such as Avellaneda, Lomas de Zamora, Lanús and Tigre are among those units likely to be most affected, in terms of potentially affected population (about 1,000,000 people), by situations of transitory flooding in a future context of a rise in the average sea level.
- Critical review of the concept of vulnerability For this research, social vulnerability has been defined based on the conditions of the social group (social, economic, cultural, political dimensions), prior to the occurrence of the catastrophic event, in terms of its “differential capacity” to face it and recover from it.
When faced with a possible disaster, the social ensemble -all those who are subject to being potentially affected by it- may be identified. The members of this group share certain features defined in terms of exposure (territorial and material aspects) but are however heterogeneous in terms of response capacity (economic, cultural, and political aspects). This ensemble is consequently heterogeneous. The differences within it must be taken into account when establishing priorities in a context of resource scarcity.
Some authors view heterogeneity in a dichotomous way, linking it to a poverty or non-poverty situation and consequently, to a situation of social inclusion/exclusion. Others identify a series of nuances and grades, in which multiple intermediate situations exist between both extremes. Who is to be included, or not, within the vulnerable group depends on the criterion to be applied. The first vision (dichotomous) considers a group and excludes another. But in reality, social vulnerability is multidimensional. Therefore, the nuances and grades that express this multi-dimensional condition should be considered.
Taking into account these previous concepts, we have performed a revision of the bibliography submitted through the different activities of the AIACC, and identified different definitions of the concept of social vulnerability. Special consideration was given to the guidelines proposed in the Technical Report Nº 3 (“Characterizing current and future vulnerability”, T. Downing et al.), and to the different ways of addressing the issue, partially summarized in the paper by T. Downing et al., Vulnerability Indices (UNEP Policy Series 3, 2001).
- Social vulnerability index: Selected definition and indicators. The social vulnerability index makes it possible to identify situations of greater social vulnerability within a given group of administrative units. Its scope and limitations are related to the objective of 22 identifying units in which the process is apparently more intense, for which reason they are more relevant and of greater interest in terms of analyzing the causes of this vulnerability.
The index includes indicators related to the following aspects: a) demography b) living conditions of the population and c) structural production and consumption processes. The indicators selected in connection with aspects a) and b) are listed below, and a brief discussion regarding their pertinence is included in Annex Task 25B.
1. Demographic aspects: 1.1. Total population 1.2. Relative population variation 1.3. Population density 1.4. Young potential dependence index 1.5. Elderly potential dependence index 2. Living conditions 2.1. Percentage of UBN (Unsatisfied Basic Needs) households 2.2. Percentage of households with women as family heads 2.3. Total child mortality rate 2.4. Neonatal mortality rate 2.5. Percentage of population without access to social security
These indicators were chosen on the basis of data availability for all the administrative units under survey, which implied reducing their number. The data employed were those corresponding to the whole of Buenos Aires province for the year 1991, the last census available to date for most of the indicators and administrative units. In all cases, a classification in five categories was made, using the system of natural breaks provided by the GIS. Then the data were plotted and classified in five categories, and the breaks were analyzed on a curve. In most cases, the categories proposed by the GIS were maintained, while in the rest of the cases they were adjusted, changing the (upper or lower) limit so as to obtain a more significant variation of the data, and consequently, the highest possible heterogeneity.
Finally, the social vulnerability index was formulated and classified according to the following table:
Social vulnerability index (preliminary) Classification Classes GIS (equal GIS (naturales intervals) breaks) Very low 15-18 15-19 Low 19-21 20-21 Medium 22-24 22-24 High 25-27 25-27
Of these two classifications, the one provided by the GIS through natural breaks was selected, since it was the one that showed greater heterogeneity in the distribution. The social vulnerability map for Buenos Aires province and that of the study area are shown in Map 3 of Annex Task 25.
3. Production and consumption processes
23 These aspects of social vulnerability have not been fully elaborated to date, and are in the process of selection and analysis. As a first step, a search for information sources on economic activities of the political-administrative units of the study area was carried out. The following sources were selected: The 1994 National Economic Census –NEC-, INDEC (National Institute for Statistics and Censuses); The 1991 National Census of Population and Housing –CNPyV-, INDEC; The 1999 Annual Report on Statistics of Buenos Aires Province, Provincial Department of Statistics, Ministry of Economy of Buenos Aires Province.
A preliminary selection includes the following indicators: Rate of unemployment Gross Added Value in $ (pesos) Jobs occupied in manufacturing industry, commerce and services Rate of activity
These indicators are discussed in Annex Task 25 B, where their pertinence to the characterization of social vulnerability is also briefly discussed.
REFERENCES Barrenechea, Julieta; Elvira, Gentile; Silvia, González y Claudia, Natenzon (2000) “Una propuesta metodológica para el estudio de la vulnerabilidad social en el marco de la teoría social del riesgo”. En: IVª Jornadas de Sociología. Facultad de Cs. Sociales; UBA. Buenos Aires, 6 al 10 de noviembre. Beck, Ulrich (1998) La sociedad del riesgo. Hacia una nueva modernidad. Barcelona, Paidós. Burton, Ian (2002) How should we frame adaptation science for policy making? Mimeo. Burton, Ian; Jones, R; Lim, B. (2002) Adaptation to climate change starts with human - environment interactions developed to cope with climate variability: A risk management approach. Mimeo. Downing, T. E. et. al. (2001) Vulnerability Indices, Climate Change, Impacts and Adaptation. Nairobi, UNEP, 92p. IPCC (2001b) Climate change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change, UNEP/WMO, Cambridge University Press, UK. Kasperson, Roger (1992) “The social amplification of risk: Progress in developing an integrative framework”. In: Krimsky & Golding, editors. Social Theories of Risk. Praeger Publishers, USA. Yohe, Gary; (2001) Indicators for Social and Economic Coping Capacity – Moving Toward a Working Definition of Adaptive Capacity. September 2001
27. Selection of sea level scenarios according to TAR IPCC (January 2003)
This task will be started in the first part of year 2003. It will be considered not only the mean sea global rise scenarios, but also the predicted regional increase in the South Atlantic.
In addition it should be considered if the coast of the Rio de la Plata is having a subsidence that might be significant in a century range. Based on radiometric dating of marine shells found at different heights above mean sea level at 15 localities distributed over more than 4,500 km, the general tendencies for the Argentina coast have been analyzed.
24 During the Holocene, the maximum transgression may have occurred between 4,000 and 6,500 yr. BP. Estimates of the relative rates of uplift for the localities range between 0,21 and 1,63 mm/yr., while the general tendency for all the coast is of the order of 0,7 mm/yr. There is clear evidence that maximum rates are associated with interbasin regions while minimum ones are found in the basins. This difference reflects the influence of neotectonic processes acting during the last 10,000 yr. The southern end of the country shows uplift rates about twice as large as those observed near Buenos Aires, indicating a differential process (Fig. 1 of Annex Task 27).
It must be noted that the Samborombón Bay lies in the Salado basin area and that during the last 6,000 years it suffered a drop in sea level of 0.61m/year, a trend that changed according to the Buenos Aires tidal map data about 1900.
28. Validation of the ETA model and the hydrodynamical models (February 2003)
CALIBRATION OF MODEL RPP-2D The calibration of model RPP-2D was undertaken through various stages, namely: i) Purely astronomical tide: comparison with water level data from Tide Tables. ii) Purely astronomical tide: comparison with recorded water level data for a calm period. iii) Normal tide condition: comparison with recorded water level and velocity. iv) Storm tide condition: comparison with recorded water level.
Purely astronomical tide from Tide Table Calibration results for this situation were presented in the previous Report.
Purely astronomical tide from records Within the time interval extending from January 1 to 31, 1985, there were detected two periods of relative calm. They can be observed in figure 1 and 2 of Annex 28, where the recorded water levels at Buenos Aires and Mar del Plata stations are compared with the water levels as predicted by the Tide Table.
The two periods are the following:
Period 1 5 to 10 January, 1985 Period 2 16 to 20 January, 1985
Results for the first period are shown in figures 3 and 4 of Annex Task 28. Though the comparison is reasonable for the present purpose, work is still going on in improving it through a better definition of the incoming tidal wave through the southern border.
Normal tide condition Current velocity records undertaken by the company Hidrovía S.A., concessionary of the maintenance dredging of the navigation channels of the Río de la Plata, were used for comparison. The measurement period runs from June to October 1996. They correspond to ten stations located relatively close to each other. In the following table the station location and corresponding period of measurement is presented.
25 Station Latitude Longitude Starts Ends Frequency 40- 35° 18’ 56° 41’24’’ 06/09/96 11:36 03/10/96 12:36 10 min 519.PRM 35’’ 10- 35°18’35’’ 56°42’0’’ 14/06/96 09:26 25/07/96 08:36 10 min 521.PRN 12- 35°16’12’’ 56°50’24’’ 14/06/96 13:21 24/07/96 10:51 10 min 518.PRN 13- 35°21’36’’ 56°43’12’’ 14/06/96 13:25 24/07/96 09:55 10 min 519.PRN 20- 35°18’36’’ 56°31’12’’ 24/07/96 11:57 13/08/96 13:17 10 min 519.PRN 24- 35°24’36’’ 56°31’12’’ 24/07/96 12:13 13/08/96 23:33 10 min 518.PRN 21- 35°11’24’’ 56°49’48’’ 25/07/96 09:25 13/08/96 18:15 10 min 521.PRN 30.519.PR 35°18’36’’ 56°41’24’’ 13/08/96 14:42 06/09/96 11:02 10 min N 315- 35°13’12’’ 56°37’12’’ 13/08/96 19:27 07/09/96 20:47 10 min 521.PRN 335- 35°19’48’’ 56°27’36’’ 14/08/96 00:36 07/09/96 20:36 10 min 518.PRN
As no wind records were available at the time of calibration, the runs were made without taking into account the wind action. Hence, only the period running from 1 to 9 July was considered, as it corresponded to a relatively calm situation. In figures 5 and 6 of Annex Task 28 the comparison between recorded and simulated eastern and northern velocity components are presented. The agreement is considered quite satisfactory. Results for the period extending from July 20 to September 7, 1996 are presented in figures 7 and 8 of Annex Task 28. Wind influence can be noted where strong departures between the two signals are observed. Work is going on to incorporate wind data, already available.
Storm tide condition Wind data obtained with preliminary ETA model results for five storm events occurred within the time interval 1980-2000 were used for simulating the associated hydrodynamic conditions. Specifically, the events are the following:
Event Date E1 06/Dic/1982 E2 06/Mar/1988 E3 12/Nov/1989 E4 31/Aug/1991 E5 16/May/2000
Each event spans along 73 hours. As the simulation results obtained with winds calculated with the preliminary ETA model were not satisfactory, the wind data base was switched to NCEP/NCAR, with a much lower resolution (see figure below). In addition, following the experience with HANSOM-CIMA model, the relatively weak intensities provided by this database were increased by 26 a factor 1+e-V/(15m/s), with V the velocity module. Figure 9 of Annex Task 28 shows the wind fields from NCEP and the ETA model.
As an illustration, figure 10 of Annex Task 28 shows water levels for Oyarvide Station, for the November 1989 storm. A satisfactory agreement is observed. Note that the level of agreement is similar to that obtained with HANSOM-CIMA, Figure 11 of Annex Task 28.
In order to separate meteorological from astronomical tidal effects, the latter ones were filtered out. In the case of water level records, the Tide Table was used. For the simulations, new runs were undertaken without considering astronomical effects. The figure 12 of Annex Task 28 allows the comparison for pure meteorological effects. It is considered as satisfactory.
29. Running of the ETA and the hydrodynamic models for the dates of the oceanographic campaign conducted by Project LA 32 as explained in point 7 of the join document (March 2003)
This activity will be implemented in the first part of 2003, once the models will completely validated.
30. Selection of some cases of typical weather storms and analysis of them with the ETA model to estimate the surface wind fields (December 2002)
Five weather storms were selected to represent different synoptic situations associated with strong southeasterly winds, which are the winds that produce floods in the Argentine coat of the RP. These situations were:
Dates Year December, 5 to 9 1982 March, 5 to 9 1988 November, 10 to 15 1989 August 29 to September 5 1991 May 14 to 20 2000
The high resolution ETA model was nested in NCEP/NCAR reanalysis of the initial day of the run, which was always 24 hours later than the earlier date shown in the preceding table. In all the cases, the resulting wind fields at surface levels show considerably less strength than the respective fields from the NCEP/NCAR reanalysis, Figures 1 and 2 of Annex Task 30. Regarding wind direction, there are no significant differences between both fields. When the wind stresses were incorporated in the hydrological models, they result insufficient to generate the wind tide observed. See report on task 28.
As a result of these experiments, it was concluded that a major revision of the conditions of the experiments is required. It is now being explored the size and shape of the domain used to run the ETA model. Other analyses are now being performed on the surface temperature cycle, which is not well reproduced, perhaps of a too general description of soil conditions. Experiments with different surface drug conditions are also performed.
27 31. Development of strong waves scenarios (October 2002)
The aim of this work was to establish the present mean conditions of sea and swell in the Rio de la Plata and to assess the possible changes in the wave climate of the Rio de la Plata due to future climate variability. The present wave climate for the outer region of the Rio de la Plata (RP) was characterized based on the single wave data set (1996–2001) available, measured by Hidrovia SA. Bidimensional distributions of heights and periods for eight wave directions clearly enabled to identify swell and sea conditions in the region. The former conditions were used as initial conditions in a numerical computer propagation and transformation program to obtain the wave characteristics in the proximity of the coast of Buenos Aires. The program includes refraction, shoaling and bottom friction.
Results show that from the outer RP upstream to Atalaya (See Fig 1 of Annex Task 31 for locations), waves are formed by a combination of sea and swell conditions. North of Atalaya, swell cannot reach the coast of Buenos Aires hence waves in this region are only locally generated (sea). The Hindcasting Methodology was applied to determine mean sea (local waves) conditions on the coast of Buenos Aires (RP). Mean winds from the 10-year climatological statistics from Aeroparque and Ponton Recalada were used. The results were conveniently validated using the in-situ wave data available. The directional wave climate was thus obtained, for the inner and intermediate RP and for the regions identified as Punta Piedras, Bahia Samborombóm and Punta Rasa.
Estimates of change in the wave climate of the Buenos Aires coast (RP) were computed under the hypothesis that for changes in local winds over the RP, swell will be considered invariable (given that they are waves incoming the estuary from very distant sites where they were formed) and only mean sea (local waves) climate will change. Details in Annex Task 31.
Travel activities
The PI of the Project V. Barros made in January a short trip (one-day) to coordinate the development scenarios activity with M. Bidegain (Task 16)
The Co-PI M. Caffera made two short trips to Buenos Aires to work with I. Camilloni and V. Barros in the extreme discharges of the Uruguay River (Task 20)
As reported in Task 18, V. Barros, S. Bischoff, A. Menendez, C. Natenzon, R. Kokot, I. Camilloni, W. Vargas, M. Re and G. Escobar attended the joint LA 26-LA 32 workshop held in Montevideo in September 25-27, 2002. The last two were funded with the collateral funds of the University of Buenos Aires Project.
As reported in task 17, V. Barros and S. Bischoff lectured in an intensive course on Climate variability and anthropic influences in Montevideo during October 2002.
Dr Menendez and Dr. Codignotto made short trips to the Samborombón bay area to make field work.. Other trips of Dr. Kokot were paid with collateral funds from the University of Buenos Aires Project.
C) Description of Difficulties Encountered and Lessons Learned 28
Task 10
We had difficulties with this task that were discussed under the Task 10 report.
Task 12
Because of the lack of available high-resolution altitude maps, the topography was digitized with a resolution of 1.25 m. This is not enough for the Project requirements and therefore, field measurements will be taken with a GPS.
Task 13
There was a delay in having some of the SRES-A2 scenarios available in the Modelle and Daten (MOD) page of IPCC. However, outputs from the ECHAM4/OPYC and from GFDL-R30 were obtained directly from the Max Planck and the Geophysical Fluid Dynamics Laboratory respectively.
One important difficulty was that, as reported under task 13, all the models considerably underestimate the precipitation over the Rio de la Plata basin. The patterns of errors with respect to the observed fields share similar features in all models. This and the nature of these patterns seem to indicate that these errors can be attributed to the low resolution of these models. Therefore an experiment with a high-resolution model will be intended.
Task 14
As anticipated in the First Report, it was not possible to have a transfer of the HamSOM model code. Therefore, it was decided to implement a similar model (3 dimensional model) with free code access, the POM model. This activity is reported under task 23.
Task 28
As explained under task 28, the ETA model, at least in our code version, underestimate surface winds and overestimate the diurnal cycle of temperature. This leads us to a new process of adjustment and validation.
D) Description of Tasks to be performed in the Next Eight-Month Period
Tasks numbers as in the working plan. It is indicated when the task was already initiated as reported in part B. In brackets the estimated end date.
10. INITIATED. Photo interpretation of dry, normal and flood events (Scale 1: 20 000 and 1: 60 000) (April 2002)
As explained in Point B, this task was made for a few cases with very high water level. The problem was that most of them had cloudy skies, and thus the satellite image was of little help to estimate 29 equal altitude lines on the terrain. In this new intent, it will be selected a wider range of cases with different water levels to asses altitude contours in low lands that are frequently subject to flooding from storm tides. These low lands in the Samborombón bay are of difficult access, and therefore, it will be difficult to take field measurements with a GPS system, as is going to be done in the rest of the area.
11. INITIATED. Data base construction in a GIS environment. Point 3 of the Joint Document. (December 2003 or later) This will be a continuous activity along the Project, including outputs of the tasks.
12. INITIATED. Topographic measurements and fieldwork will be carried out to produce detailed altitude level maps of coastal areas subject to possible floods (April 2003)
The maps reported in task 12, point B are going to upgraded with higher resolution as a result of field measurements to be taken with a GPS system, images from Landsat satellites 5 and 7, and interpolation based on geomorphology.
13. INITIATED. Election of future climate scenarios in cooperation with Project L32 (June 2003)
1) Annual and monthly mean sea level scenarios for the periods 2000-2050 and 2050-2100 will be computed from the four models selected, as it was explained in Part B of the Report.
2) From the sea level scenarios, it will be developed their respective surface wind scenarios.
3) With daily data from at least two models, it will be assessed the performance of these models to reproduce the statistical features of the synoptic situations that lead to strong easterly and southeasterly winds over the Rio de la Plata and the adjacent ocean.
4) If the models performance of the features described in 3 were satisfactory, the statistics of these synoptic situations will be estimated for the 2000-2050 and 2050 and 2100 scenarios. Otherwise, it will be used an incremental approach with respect to present statistics.
Regarding precipitation, as explained in task 13 of part B of this report, it will be intended to develop a high-resolution scenario. This activity will take the whole year 2003.
16. INITIATED. Development of future scenarios for the Paraná delta growth. (December 2003)
The past evolution of the Delta during the last 300 years is going to be completed by July. Future evolution od the Delta will depend on many variables, one of the most important is the future level of waters in the inner estuary of the Rio de la Plata. Therefore, scenarios will be constructed after tasks 32 and 33 will be well advanced.
21. INITIATED. Writing of a paper manuscript on extreme streamflow events in the Paraná and Uruguay rivers (April 2003) 30
The paper on the Paraná River was already written. Remains the manuscript on the Uruguay River.
22. INITIATED. Consultation about demands and communication of Project partial results with stakeholders through mail and email (March 2003)
This task is almost completed, but it will be continued with a consultation to a greater group of stakeholders. In March 2003, a one-day workshop will be held to present the Project results to stakeholders and to receive from them suggestions and demands. Forty participants from 30 governmental and non-governmental organizations will be invited. In the same workshop, it will also be presented results from the University of Buenos Aires Project on Floods on the Paraná and Uruguay Rivers that provide the collateral funds to the Project.
22. INITIATED Develop of a Social Vulnerability Index to flooding in a GIS environment. Point 3 of the Joint Document (July 2003)
The social vulnerability index is going to be improved by the inclusion of indicators of production and consume.
27. INITIATED Selection of sea level scenarios according to TAR IPCC (June 2003)
This task will be undertaken, once the subsidence of the Argentine coast of the Rio de la Plata will be conveniently assessed.
28. INITIATED Validation of the ETA model and the hydrodynamic models (April 2003)
It remains to calibrate the ETA model in order to get appropriated surface winds to force the hydro- dynamical models
29. Running of the ETA and the hydrodynamic models for the dates of the oceanographic campaigns conducted by Project LA32 as explained in point 7 of the joint document (June 2003)
32. Development of mean and extreme scenarios of water level with hydrodynamic models (July 2003)
33. Development of extreme scenarios of water level with hydrodynamic models under different storm weather scenarios (July 2003)
34. Writing a manuscript on the future mean and extreme scenarios of water level (August 2003)
31 35. Engineering implications and prospective of the geomorphological evolution of coastal area complementing the geologist point of view. This includes both the new coastal geography arising from sea level rise and the advancement of the Paraná Delta front (December 2003)
36. Identification of critical zones of social vulnerability to flooding (July 2003)
E) Anticipated Difficulties in the Next Eight-Month Period Task 13
The running of a high-resolution regional model nested in outputs from GCMs of lower resolution implies a great challenge because of many factors, related to the availability of computational resources and lack of sufficient experience in such activity.
Sensitivity analysis indicates that only the greatest and exceptional discharges have some influence on the Rio de la Plata level. On top of that, Task 20 showed that these exceptional discharges are closely related to El Niño events. Therefore, a shortcut could be taken, to estimate the frequency of the exceptional discharges if the GCMs properly represent the ENSO phases.
F) Collateral Funds As explained when the Project was submitted to AIACC, The University of Buenos Aires through a Program of Special Projects have been granted funds to a Project with similar objectives but with a large geographical scope because includes the study of floods of the Uruguay and Paraná and Paraguay rivers. The PI is the same as in the AIACC LA 26 Project and so are the Co-Pi that work in the University of Buenos Aires. Due to the economic difficulties of the country during the last year, the granted funds were not available to the Project until July 2002. Nevertheless, these funds were very useful to upgrade computers and to grant fellowships to 3 students that participate of Tasks 13, 16 and 23. These funds will only be available util December 2003 and will be applied to buy a GPS and to increase the number of fellowships.
G) Connections with the National Communication According to the instructions, I paste the answers I sent a few weeks ago
Connections between the Project and the preparation of the National Communication under the UNFCCC for countries relevant to your project
For the time being, the plans for the preparation of the UNFCCC are managed by the Foreign Affairs Ministry we had the support of the Foreign Affairs Ministry for our project when presented to AIACC and we keep them informed about our project.
Members of the Project team that assisted with the first national communication
32 Vicente Barros was the national director of the PNUD Project Arg/95/g/31 funded by GEF as an enabling activity to produce the First National Communication to the UBFCCC of Argentina. Walter Vargas was one of the two coordinators of Project Arg/95/g/31. Vicente Barros wrote the draft of the first national communication. Vicente Barros made the evaluation of the first communication OFD Uruguay on behalf of PNUD.
Participants in the second national communication
Argentina did not present yet the second communication. However in 1999 presented to the UNFCCC a revision of the First National Communication. In such revision the GHG inventories of 1990 and 1994 were revised and a new inventory of 1997 was reported. Vicente Barros coordinated the project and prepare the draft for the revision of the first national communication.
Rapport with committees or persons responsible for national communications about the AIACC Project
In Argentina is not clear who is responsible for this activity. The plans for the Second Communication were being made in the Foreign Affairs Ministry by Dr. Estrada Oyuela. Recently, it was also incorporated the Secretary of Environment. Vicente Barros and Walter Vargas participated of informative meetings at the Foreign Ministry were the first steps of the planning activity were reported to key experts.
Plans for communicating in the future with Committees or personsin charge of the Second national Communication about the AIACC project
It is planned that a steering committee will be establish to direct the Second Communication activities. We expect to continue participating of the informative meetings with the steering committee .
Input to committees or persons responsible for national communication to the objectives, methods or plans from the AIACC project
In a panel on climate change and vulnerability in Buenos Aires about November 2001, Dra Bischoff of our team described the project other panel member was Dr. Estrada Oyuela who found important to include part of the objectives of the AIACC LA 26 Project in the Second Communication
Future input of the Project to committees or persons responsible for the National Communication
There were not specific requirements. Though we expect them after the steering committee is established
Commitment to use information from the Project in the preparation of the Second National Communication
33
There is no yet a formal commitment, but we learnt in the informative meetings that it will be a selection of groups of national experts for each vulnerability activity based on their qualifications. Walter Vargas, Claudia Natenzon; Angel Menéndez, Susana Bischoff and Jorge Codignotto are considering to make a proposal as a group to participate of a vulnerability study related to our project. We do not know if other group of experts will make a proposal in this subject. We consider this very unlikely because of the limited human resources in the field. In any case, the Project results will be public since we are preparing reports to the University of Buenos Aires similar to those that are regularly submitted to AIACC. This implies a public access to the reports. For instance, as a part of an external evaluation, the University of Buenos Aires held a meeting with stakeholders in October 2002. In that meeting we were asked to present our results. The project is going to have a similar meeting in march 2003. The aim will be to present results and get input from stakeholders. this time the steering committee of the second national communication if established will be invited. Other members of our team are considering to participate in other activities of the second national communication with other groups of experts, Vicente Barros in the 2000 GHGs inventory and Ines Camilloni in vulnerability to floods in the great rivers of the northeast of Argentina
H) Attached Documents Fifteen annexes with more detailed information about the tasks reported in point B of the document are attached.
34 ANNEX TASK 12
Figure 1. Topographic map of Samborombón Bay.
Figure 2. Topograhic map between Buenos Aires City and Punta Piedras.
Annex 13
SLP - HADCM3-NCEP - JANUARY (1950-2000) SLP - HADCM3-NCEP -APRIL (1950-2000) -20 -20
-25 -25
-30 -30 E E D D U U T T I I T T A A L -35 L -35
-40 -40
-45 -45
-65 -60 -55 -50 -45 -65 -60 -55 -50 -45 LONGITUDE LONGITUDE
SLP - HADCM3-NCEP - JULY (1950-2000) SLP - HADCM3-NCEP -OCTOBER (1950-2000) -20 -20
-25 -25
-30 -30 E E D D U U T T I I T T A A L -35 L -35
-40 -40
-45 -45
-65 -60 -55 -50 -45 -65 -60 -55 -50 -45 LONGITUDE LONGITUDE
Figure 1. SLP difference fields (hPa) between the HADCM3 model data and the NCEP reanalyses for January, April, July and October.
SLP - CSIRO MK2-NCEP -JANUARY (1961-2000) SLP - CSIRO MK2-NCEP -APRIL (1961-2000) -20 -20
-25 -25
-30 -30 E E D D U U T I T I T T A A L L -35 -35
-40 -40
-45 -45
-65 -60 -55 -50 -45 -65 -60 -55 -50 -45 LONGITUDE LONGITUDE
SLP - CSIRO MK2-NCEP -JULY (1961-2000) SLP - CSIRO MK2-NCEP -OCTOBER (1961-2000) -20 -20
-25 -25
-30 -30 E E D D U U T T I I T T A A L L -35 -35
-40 -40
-45 -45
-65 -60 -55 -50 -45 -65 -60 -55 -50 -45 LONGITUDE LONGITUDE
Figure 2. SLP difference fields (hPa) between the CSIRO-mk2 model data and the NCEP reanalyses for January, April, July and October.
SLP - ECHAM4-NCEP -JANUARY (1990-2000) SLP - ECHAM4-NCEP -APRIL (1990-2000) -20 -20
-25 -25
-30 -30 E E D D U U T T I I T T A A L -35 L -35
-40 -40
-45 -45
-65 -60 -55 -50 -45 -65 -60 -55 -50 -45 LONGITUDE LONGITUDE
SLP - ECHAM4-NCEP -JULY (1990-2000) SLP - ECHAM4-NCEP -OCTOBER (1990-2000) -20 -20
-25 -25
-30 -30 E E D D U U T T I I T T A A L -35 L -35
-40 -40
-45 -45
-65 -60 -55 -50 -45 -65 -60 -55 -50 -45 LONGITUDE LONGITUDE
Figure 3. SLP difference fields (hPa) between the ECHAM4/OPYC3 model data and the NCEP reanalyses for January, April, July and October.
SLP - GFDL R30-NCEP -JANUARY (1961-2000) SLP - GFDL R30-NCEP - APRIL (1961-2000) -20 -20
-25 -25
-30 -30 E E D D U U T I T I T T A A
L -35 L -35
-40 -40
-45 -45
-65 -60 -55 -50 -45 -65 -60 -55 -50 -45 LONGITUDE LONGITUDE
SLP - GFDL R30-NCEP - JULY (1961-2000) SLP - GFDL R30-NCEP - OCTOBER (1961-2000) -20 -20
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Figure 4. SLP difference fields (hPa) between the GFDL-R30 model data and the NCEP reanalyses for January, April, July and October.
Figure 5. SLP difference fields (hPa) between the L8-LMD model data and the NCEP reanalyses for January, April, July and October.
SLP - HADCM3-NCEP - ANNUAL (1950-2000) SLP -CSIRO mk2-NCEP - ANNUAL (1950-2000) -20 -20
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-30 -30 E E D D U U T T I I T T A A L L -35 -35
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SLP - ECHAM4-NCEP - ANNUAL (1950-2000) SLP - GFDL R30-NCEP - ANNUAL (1950-2000) -20 -20
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-65 -60 -55 -50 -45 -65 -60 -55 -50 -45 LONGITUDE LONGITUDE
Figure 6. Annual mean SLP difference fields (hPa) between the HADCM3, ECHAM4/OPYC3, CSIRO-mk2 and GFDL-R30 model data and the NCEP reanalyses.
PP HADCM3-UDEL -JANUARY (1950-1999) (mm/dy) PP HADCM3-UDEL -APRIL (1950-1999) (mm/dy) -10 -10
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PP HADCM3-UDEL -JULY (1950-1999) (mm/dy) PP HADCM3-UDEL -OCTOBER (1950-1999) (mm/dy) -10 -10
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Figure7. Precipitation difference fields (mm/day) between the HADCM3 model data and the University of Delaware rainfall dataset for January, April, July and October.
PP CSIRO-UDEL -JANUARY (1961-1999) (mm/dy) PP CSIRO-UDEL -APRIL (1961-1999) (mm/dy) -10 -10
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PP CSIRO-UDEL -JULY (1961-1999) (mm/dy) PP CSIRO-UDEL -OCTOBER (1961-1999) (mm/dy) -10 -10
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Figure 8. Precipitation difference fields (mm/day) between the CSIRO-mk2 model data and the University of Delaware rainfall dataset for January, April, July and October.
PP ECHAM4-UDEL -JANUARY (1990-1999) (mm/dy) PP ECHAM4-UDEL -APRIL (1990-1999) (mm/dy) -10 -10
-15 -15
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PP ECHAM4-UDEL -JULY (1990-1999) (mm/dy) PP ECHAM4-UDEL -OCTOBER (1990-1999) (mm/dy) -10 -10
-15 -15
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Figure 9. Precipitation difference fields (mm/day) between the ECHAM4 model data and the University of Delaware rainfall dataset for January, April, July and October.
PP GFDL R30-UDEL -JANUARY (1961-1999) (mm/dy) PP GFDL R30-UDEL -APRIL (1961-1999) (mm/dy) -10 -10
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PP GFDL R30-UDEL -JULY (1961-1999) (mm/dy) PP GFDL R30-UDEL -OCTOBER (1961-1999) (mm/dy) -10 -10
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Figure 10. Precipitation difference fields (mm/day) between the GFDL-R30 model data and the University of Delaware rainfall dataset for January, April, July and October.
PP HADCM3-UDEL - ANNUAL (1961-1999) (mm/dy) PP CSIRO-UDEL - ANNUAL (1961-1999) (mm/dy) -10 -10
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PP ECHAM4-UDEL - ANNUAL (1961-1999) (mm/dy) PP GFDL R30-UDEL - ANNUAL (1961-1999) (mm/dy) -10 -10
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Figure 11. Annual mean precipitation difference fields (mm/day) between the HADCM3, ECHAM4/OPYC3, CSIRO-mk2 and GFDL-R30 model data and the NCEP reanalyses.
ANNEX TASK 14
: Fig. 3 Domains for the three HANSOM-CIMA nested models .
Fig. 2. Comparison between observations (black) and outputs from HamSOM models at stations Palermo, Oyarvide, San Clemente and La Plata during the storm of May 2000.. In blue model results when wind forcing is included in domains B and C, while in red when this forcing is included in the three domains A, B y C.
2 ANNEX TASK 16
Figure 1. Location Map of Paraná Delta Front.
3
Figure 2 Delta Progradation of Paraná River (Reference Point: mouth of Reconquista River
Delta Progradation
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
Delta Progradation (km.) 1.0
0.0 1880 1900 1920 1940 1960 1980 2000 Year
4 ANNEX TASK 17 MASTER ON ENVIRONMENTAL SCIENCES FACULTY OF SCIENCES, UNIVERSITY OF LA REPÚBLICA
PROJECTS AIACC LA 26 and LA 32
Climate variability: Human effects and evaluation of vulnerability and adaptation
Coordinator: Dr (Ocean) Gustavo Nagy (FC-UdelaR, Uruguay) Lecturers: Dr. (Met) Vicente Barros, Dr. Susana Bischoff (FCEN, UBA) Argentina MSc (Clim) Mario Bidegain, MSc (Env) Mario R. Caffera Ec. MSc (Rec Nat) Gustavo Sención, Dr. Gustavo Nagy, (FC-UdelaR) Uruguay
Introduction What is Global Change? Importance of present climate variability and of its vulnerability and adaptation assessment.
1. The Climate System Elements of climate. The climate systems and subsystems. Radiation in the climate system. Solar radiation. Diffusion in the atmosphere. Absorption. Optical depth. Reflection. Terrestrial radiation. Radiation balance. Hydrosphere, Criosphere and Lithosphere. Meridional transport of heat and energy and its climatic implications
2. Causes of Climate Variability Terrestrial orbit variations. Solar radiation variability. Uplifting and continental drifting. Volcanism and atmospheric composition variability. Internal variability. Feedback mechanisms. Predictability. Transitivity and attractors. Consequences of the semi-transitive features of the atmosphere.
3. The Observed Climate Variability and its Impacts Global temperature in geological eras. Ice ages. The last 50 M years. The present ice age. Glacial and interglacial periods. The optimum thermal of the Holocene. The climate changes at the beginning of civilizations. The extinction of the Viking colony in Greenland. The end of the optimal thermal in the Middle Age and the Small Ice age: Social and economic impacts in Europe. Other cases of climate change impact in history. Features of the climate variability in the instrumental period. Interannual variability and trends.
4. The Global Warming (‘Climate Change’) The problem. Green house gases (GHG). The radiation forcing. GHG lifetime. Chemistry and other sinking mechanisms. The geo-chemical cycle of the main GHGs. Aerosols. The observed climate changes. Attribution of the observed climate change. The future climate. Impacts.
5. The International Response to Climate Change GHG emission sources from different productive sectors. Technological prospective: Primary sources of energy. Generation of secondary energies, transport and consume of energy. Agriculture and carbon sinks. The interests at play in climate change: Productive sectors, equity and ideological aspects. The position and interests of some countries. The United Nation Framework Convention on Climate Change. The role of the multilateral organisms: The IPCC and GEF. The Kyoto Protocol. The flexibility mechanisms: The carbon market. The Kyoto Protocol ratification.
5 6. Uruguay, Argentina and the Climate Change The changes and recent trends: their impacts. Regional vulnerability to Climate Change. Governmental response. Profile of GHG emissions. Mitigation options.
7. El Niño – Southern Oscillation (ENSO) Sea-atmosphere interaction in the tropical Pacific. Impacts in the inter-annual climate variability. Influence of ENSO phases in the regional climate variability (Eastern South America). Other patterns of Climate variability.
8. Climate Models and Scenarios The XXI century climate. Projections and SRES scenarios. Climate models. Precipitation, temperature and sea level pressure scenarios for eastern South America.
9. Socioeconomic Scenarios Global socioeconomic scenarios. Projections or outlooks into the future world. SRES scenarios (A1, A2, B1 and B2) National SRES scenario (A1 2000-2050). Socioeconomic scenarios for the assessment of vulnerability and adaptation.
10. Assessment of vulnerability and adaptation to Climate Change Vulnerability and adaptation definitions. Frameworks for vulnerability studies. Elements of the vulnerability. Concepts, problems and methods for the vulnerability assessment and adaptation. Vulnerability indexes
6 ANNEX TASK 19
CLIMATIC AND SYNOPTIC DIAGNOSIS OF SUDESTADAS IN THE RIO DE LA PLATA Gustavo Escobar (*) Departamento de Ciencias de la Atmósfera y los Océanos Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires Tel. 54 11 4576 3364 ext Fax 54 11 4576 3364 ext 21 e-mail: [email protected]
Walter Vargas Departamento de Ciencias de la Atmósfera y los Océanos Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires CONICET Tel. 54 11 4576 3364 ext 30 Fax 54 11 4576 3364 ext 21 e-mail: [email protected]
Susana Bischoff Departamento de Ciencias de la Atmósfera y los Océanos Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires Tel. 54 11 4576 3364 ext 18 Fax 54 11 4576 3364 ext 21 e-mail: [email protected]
7
1.-Introduction
The sudestada is a phenomenon which affects the coastal zone of the Rio de la Plata, flooding its shores and causing severe damage to the population, not only on the coast but also to a great number of inhabitants of the city of Buenos Aires and greater Buenos Aires and both merchant and sports navigation. It is associated to strong, persistent winds from the east - south quadrant and it is often accompanied by rainfall.
This phenomenon may be quantified either by calculating a. the associated social and economic impact or b. the level reached by the Rio de la Plata in each case.
In the latter case the level of the Rio de la Plata is taken at the Palermo tidal gauge (Riachuelo Dock F (j= 34º34’S, l = 58º23’W) (Naval Hydrography Institute Figure 1) identifying the different risk levels according to Balay (1961):
2.50 m = alert level 2.80 m = emergency level 3.20 m = evacuation level
Studies referring particularly to sudestadas on the Rio de la Plata can be found in Celemin (1984) who compiles and describes synoptically the sudestadas from 1940 to 1982 and classifies their intensity according to the strength of the wind, the fraction of sky covered by clouds and rainfall.
mild: ½V½Þ 10 1 15 kt, overcast sky, moderate: ½V½Þ 15 a 30 kt, cloudy sky and some precipitation, strong: ½V½Þ >30 kt, precipitation in the whole region.
Ciappesoni and Salio (1997) made the first systematic study of sudestadas and circulation fields in the middle troposphere in a 5 year sample (1990-1994). To make this study the authors used a Rio de la Plata level higher than 2.50 m at the Riachuelo Dock F and divided the sudestadas using the Celemin classification (1984).
8 Related to this event but stressing associated circulation aspects, Schwerdtfeger (1954), Rivero and Bischoff (1971), Necco (1982), Jusem and Atlas (1991) and Seluchi (1995) studied the occurrence of cyclonic vortices in South America and particularly cyclogenesis over northeastern Argentina. In this paper the authors want to add to the knowledge of sudestadas by developing a Climatology which will make it possible to differentiate associated circulation prototypes using the NCEP/NCAR database for 1951/2000 and the hydrological data from the Naval Hydrography Institute database which define the occurrence of the sudestadas.
2.-Parameters and data
To estimate the levels of the Rio de la Plata it is necessary to take the definitions established for the different components of this variable:
Astronomical tide: sea level fluctuation caused by astronomical effect obtained from the tide gauge.
Storm surge: real river level – level of the astronomical tide.
The storm surge depends on the intensity and persistence of the wind from the east-south quadrant in the Rio de la Plata and defines the meteorological sudestada. This always causes water level elevations so we may consider the existence of a biunivocal relation between a sudestada and a water level elevation in the Rio de la Plata. Data from the Naval Hydrography Institute (1951/2000) were used in this paper (1962/1963 are missing).
· height of the storm surge · time at which peak storm surge occurred · observed level of the Rio de la Plata obtained from the tide gauge · duration of event in hours
9 In all cases the Rio de la Plata level was associated to winds in the east -south quadrant. For this reason the appraisal of the behavior of the parameters obtained from the SHN data will be made using the definition of sudestada in relation to storm surge height. During the process of development, maturity and waning of the sudestadas there is an increase and a decrease of the values that define a storm surge and a rise followed by a drop in the level of the Rio de la Plata. The behavior of the two variables, however, does not always occur in the same phase and sometimes the peak storm surge comes before or at the same time as the peak water level rise of the Rio de la Plata (Ciappesoni-Salio, 1997).
3.- Analysis of sudestadas in the Rio de la Plata
In order to determine the characteristics of the behavior of sudestadas, the selected cases were studied starting with the storm surge, in the whole period for which the data are available.
Storm surge over 1.60m Persistence for more than 24 hours Number of cases: 297
The annual distribution of sudestadas according to the criterion established appears in Figure 2. Peak occurrence may be observed during the summer and at the beginning of spring and autumn. This behavior is most frequently accompanied with surface winds in the east-south quadrant as shown by the statistics at the Aeroparque station (j= 34°34’S, l= 58°25’W). Table I shows the monthly climatic frequency corresponding to 1981/1990. With climatic data on the annual progress of the monthly distribution of sudestadas, the annual frequency progress was calculated for the different decades in order to study variability on that scale and then measure the stability of monthly distribution frequencies. Figure 3 shows decadal frequency of water level elevations with a storm surge of more than 1.60 m. It shows a peak frequency in the 1951-1960 decade. During the following decade there is a reduction in absolute frequency but it must be remembered that there is no information for 1962 and 1963 so that this relative minimum does not seem to be representative. However, a correction for the number of years shows the same low. In the 3 following decades there is an increase in absolute frequency going from 57 cases in 1971-1980 to 79 cases in 1990 – 2000.
10 For the analysis of another statistical feature of the sudestadas, Figure 4 shows the distribution of the storm surge heights. The distribution parameters reached the following values: mean = 193 cm., minimum = 161 cm., maximum = 348 cm., standard deviation = 28.9 cm. The distribution has a negative exponential shape with rare cases of surges higher than 300 cm. The probability that the storm surge reach a height from 200 to 300 cm. is l5.1%. This indicates certain characteristics of the circulation fields which mark how far the circulation may be qualified as rare. The duration of the sudestadas associated to storm surges higher than 1.60 m. is a measure of the possible impact as regards running off of tributaries. Figure 5 shows the duration frequencies in 20 hour intervals with a variation range of 150 hours. The distribution of durations is expressed in hours. The distribution parameters reached the following values: mean = 47 hours, minimum = 25 hours, peak = 175 hours, standard deviation = 22 hours. As in the previous case, the distribution is negatively exponential showing that durations longer than 60 hours are only reached with a probability of 20.5%. Persistence of 20 to 60 hours determines the most probable ranges (they occur in 79.1%) to be considered when estimating risks. Since extreme events imply a greater impact and are rarer it is necessary to study whether under more restrictive conditions in the definition of water level rise the features found are preserved or changed. Which is why we define peak rise as: Storm surge greater than 2.05 m. Persistence greater than 24 hours Number of cases: 72
The selection of this minimum spot height of the storm surge corresponds to the minimum value of the upper quartile determined using the climatic distribution of all the values available of storm surge levels and the events thus defined will be called extreme storm surge events. The annual distribution of sudestadas according to this criterion is shown in Figure 6. New occurrence peaks can be observed at the end of summer and spring. This indicates that the statistical structure of the sudestadas is maintained for the different thresholds of the storm surge values taken in this case. The decadal distribution shows, as in the previous case, that the absolute frequency of the most extreme sudestadas increases successively in the last three decades. This behavior may be observed in Figure 7.
11 4.- Circulation and sudestadas
To identify the circulation fields associated to extreme storm surges 12-hourly NCEP – NCAR reanalyses (00 and 12UTC) in the 1951 to 2000 period were used. Circulation was analyzed at the 1000 hPa level in the 20° to 60° S latitude, 130° to 40° W longitude domain at points of the 2.5° x 2.5° lat-long grid. Following the Celemin definition, the occurrence dates of the sudestadas for which synoptic situations were selected were: 26/8/51 31/5/52 13/1/53 8/9/54 22/10/55 25/11/56 13/1/57 27/7/58 19/2/59 14/4/59 10/5/59 18/8/72 2/10/80 12/9/81 5/11/81 22/2/82 19/6/82 17/9/90 6/10/90 23/10/90 5/11/90 27/11/90 2/6/91 31/8/91 15/1/92 22/3/92 17/1/93 7/2/93 20/2/93 1/3/93 20/3/93 29/3/93 3/4/93 15/4/93 9/6/93 30/8/93 1/3/94 31/8/94 10/3/98 17/9/98 5/12/98 28/6/99 29/10/99 8/7/00
The day of the event is day 0. For each event sequences were selected every 12 hours in 1000 hPa geopotential height maps starting at 9 p.m. of the day previous to the event (00 GMT of day 0) and ending at 9 a.m. of the following day (12 GMT of day 1).
The 1000 hPa geopotential height fields associated to each of the dates of the sudestadas were then averaged for every hour. In this way the average sequence of the 1000 hPa height fields was obtained (Figure 8). The sequence of the mean pressure field shows the entry of an anticyclone with W – SW axis which eventually could be associated to a baroclinic zone which on day 0 lies at 00Z over the south of Brazil. With this pressure configuration over the Rio de la Plata moderate winds which persist and intensify with the passing of time blow from SE. On the other hand, in the NE of Argentina, a low pressure zone is observed which together with the anticyclone described previously create a region with a strong pressure gradient causing moderate SE winds over the Rio de la Plata.
12 Another feature of importance is the intensification of the anticyclone which, on entering the continent, reaches its peak on day 1 at 00 Z over the south of the Province of Buenos Aires. This anticyclone separates from the Subtropical Anticyclone of the South Pacific and enters the continent along roughly parallel 40ºS. The above description responds to the mean surface motion field associated to sudestadas over the Rio de la Plata estuary. However, the individual analysis of each event shows a significant variability with respect to the composite field which it is necessary to divide into modes or models responsible for parts of this variability.
5.- Surface circulation associated to sudestadas in the Rio de la Plata estuary: determination of the main variation modes
5.a) Classification of events
Having defined sudestadas, it is necessary to examine first the mean conditions of this circulation feature using mean fields and their variability during the whole period covered by the information and then to try to make a stratification which would be as stable as possible using objective techniques. These should make it possible to separate dominant prototypes or models in the partial samples and in the whole. On this occasion the data used cover the 1951 - 2000 period (1962 and 1963 are missing), the occurrence date and the time the peak storm surge occurs, the height of the storm surge, the water level observed (using a tide gauge), the duration of the event in hours and the maps of the selected pressure levels.
For the first classification those cases were selected in which the sudestada persisted at least than 24 hours and the storm surge was higher than 160 cm. This spot height was chosen by the Naval Hydrographic Institute. 297 cases were found in the whole 1951 to 2000 period. Associated synoptic situations were selected according to the dates of the sudestadas. Geopotential height data were taken every 6 hours (00Z, 06 Z, 12 Z and 18 Z) at 1000 hPa from NCEP – NCAR reanalyses for 1951 – 2000. The domain used was between latitudes 20º S and 60º S and the 80º W and 40º W meridians and the information was distributed on 2.5º latitude x 2.5º longitude grid points. As local time of peak river level rise was available for each occurrence, the reanalysis data of Z time closest to the local time was used.
5 b) Mean 1000 hPa geopotential height fields
13
In view of the difficulty of interpreting surface pressure fields, the 1000 pHa fields were chosen because they are the closest to the former and have the same structure, although at a limit level, for the appraisal of winds associated to sudestadas. The total mean 1000 hPa geopotential height field and the average fields associated to extreme sudestadas by decade (Figure 9 a to f) were calculated. The mean 1000 hPa geopotential height field shows a cyclone centered in the south of the Province of Buenos Aires over parallel 40º S. With this pressure configuration, the Rio de la Plata is affected by moderate SE winds which cause water level elevations over the estuary area. These pressure fields also create a very peculiar structure when compared with the mean fields of the total sample. The latter fields show western or mild northeast winds or calm principally at the southern edge of the anticyclone (which is the area with SE winds during the sudestadas). According to this, it is already possible to say that this circulation structure associated to a sudestada is an important anomaly in the mean circulation state. When mean fields associated to sudestadas are analyzed by decades, similar features are observed in general terms. Some differences however can be seen such as a weakening of the anticyclone during the 51/60 period (Figure 9 b) and a slight strengthening of the pressure gradient over the estuary in the 61/70, 81/90 and 91/00 decades (Figure 9 c, e and f). These results should reflect changes in the frequency of sudestadas or at least in their intensity. In fact, figure 2 shows that the frequencies or number of sudestadas per decade are concurrent with the increase or reduction of the intensity of the above mentioned anticyclone. Increases were mainly observed in the last two decades.
5.c) 1000 hPa circulation field variability associated to sudestadas
The above description of the mean surface motion field associated to sudestadas in the Rio de la Plata estuary shows little interdecadal variability. Apart from the interdecadal variability observed in the circulation field associated to the occurrence of sudestadas, it is possible to observe the variability between each event. One way of synthesizing this surface circulation variability associated to sudestadas in the Rio de la Plata is to use a methodology which makes it possible to obtain the modes of circulation field variations in a relation orthogonal to each other.
14 To be able to determine the circulations or groups of them responsible for this variability, the main modes of surface circulation variation associated to extreme sudestadas in the Rio de la Plata are obtained. This was done by T-mode Principal Component (PC) Analysis. (Green et al, 1978). To this end, 297 1000 hPa geopotential height fields associated to the 297 selected sudestadas were studied. Then, applying this objective classification method, the main patterns (PCs) of 1000 hPa geopotential height were obtained. Figure 10 (left) shows the first three PCs associated to the principal circulation modes in the atmosphere when a sudestada occurs in the Rio de la Plata and the explained variance for each mode. Figure 10 (right) shows the composition of associated cases for each of these components. PC 1 which explains 33.4% of the variance (upper left panel in Figure 10) shows a model representing an anticyclone over the center of the Province of Buenos Aires which causes SE winds in the Rio de la Plata. In view of the pressure configuration, this anticyclone which is presumably post-frontal enters the continent around parallel 35º S and joins the cold front in the south of Brazil. Figure 10 too (upper right panel) shows the composition of cases associated to this circulation pattern. It shows clearly a low pressure region associated to the cold surface front which extends from the NW to the SE, from Paraguay to the southern Atlantic Ocean.
PC 2 which explains the 29.2% of the variance (Figure 10 center left panel) presents a model which represents a more intense high pressure system on the continent and a deep low- pressure system in the south Atlantic ocean with its center at approximately 55º S, 45º W. With this surface pressure configuration there is a strong irruption of cold air in the whole south of the country, producing S/SE winds in the Rio de la Plata estuary. Finally, PC 3 which explains the 13% variance (Figure 10 bottom left panel) presents a model similar to a well defined low pressure system over Uruguay associated to cyclogenesis in northeastern Argentina. At the same time, a strong anticyclone can be seen in Argentine Patagonia with its center at about 47º S. Both intense pressure systems (extratropical cyclone over northeastern Argentina and high pressure in the south of the country) generate a strong pressure gradient over the NE of the province of Buenos Aires causing strong SE winds over the Rio de la Plata (as shown by the fields associated with the highest correlation coefficient). As the results show, the circulation variability and consequently the occurrence of sudestadas can be classified with acceptable precision using an objective method.
15 Annual distribution of major 1000 hPa circulation modes associated to sudestadas
The annual distribution of sudestadas associated to each of the major circulation modes obtained from the classification was analyzed. The selection of cases for each mode was made considering the series of loading factors of each one of the three PCs starting with correlations greater than 0.65. According to this criterion, 107 cases were obtained for mode 1, 85 for mode 2 and 18 for mode 3. Figure 11 shows the series of loading factors which determine to which mode events belong according to the data given in previous paragraphs. No low frequency variability were found in the series although in mode 3 high correlations are more frequent towards the end of the period studied which means a variation in climate climatic jump in the circulation under study. Figure 12 shows the annual distribution of sudestadas for each of the 3 circulation modes. The distribution shows that mode 1 (Figure 12, above) predominates during the summer and in August and November. Mode 2 (Figure 12 center) shows two peaks in autumn and spring. On the other hand, as can be seen from comparing this with Figure 2 these two modes determine the annual storm surge frequency variation. Finally, Mode 3 (Figure 12, below) prevails in winter and has few events in the summer. This is due to the presence of a low pressure system and consequently a more marked baroclinicity that occurs almost only in winter. The statistical features of the 3 modes are shown in Table II: Although the circulations corresponding to mode 3 do not produce the maximum height absolute, the middle and minimum values are the highest implying that the presence of low pressures changes the properties of associated sudestadas.
Conclusions
The Rio de la Plata sudestadas are very important climatic and hydrological phenomena because of the mostly negative impact they produce, especially in the most acute cases and phases. From the point of view of the general circulation of atmosphere, the circulation associated to them, constitutes a mean field anomaly of great importance on the synoptic scale as winds with an eastern component appear in a region that is usually dominated by different wind directions. On the other hand, this property makes study methods and discrimination of the circulation
16 variability modes easier as they form separable samples which can therefore be treated by orthogonal methods.
The results show that sudestadas are basically formed by a combination of a high pressure system to the south of the river and a relative or very deep low pressure zone to the north of the river, which give rise to winds from the SE sector and produce special hydrological effects on the estuary and further up the Rio de la Plata.
The sudestadas occur during the whole year, the least frequently in winter. The ones that do occur in winter however have a special characteristic: they have an intense and considerably developed low pressure system which occurs rarely and forecasting their consequences is difficult. This may be seen and confirmed in the mode structures which explain most of the variability of the sudestadas sample since it is mode 3 which generates the said circulation. This would indicate that the greatest frequency of extreme sudestadas is associated to the development of low pressure systems to the north of the Rio de la Plata.
Decadal variability is lowest from 1960 to 1970 and increases after that, suggesting a low frequency change. Although this is not proved here, the increased occurrence of mode 3 in recent years supports it.
The similarity of statistical structures and resulting modes for storm surge heights of more than 160 cm. show a degree of stability and similarity of meteorological processes between the occurrence of extreme sudestadas and the ones with lower values.
It would be useful to define one or various indices identifying sudestada circulation in past geopotential height fields to obtain a way of generating a sudestada probability scenario in the Rio de la Plata using computational models for the future.
Aknowledgments
This work was funded by Assessments of Impacts and Adaptations to Climate Change, a project of the Global Environment Facility that is implemented by the United Nations Environment Programme and co-executed by START and the Third World Academy of Sciences. The
17 opinions expressed herein reflect those of the authors and do not necessarily reflect the views of the sponsoring organizations. The authors are grateful to Dr. Vicente R. Barros for his helpful and ideas, comments and discussions on many topics of this study.
References
- Balay, Marciano A.: El Río de la Plata entre la atmósfera y el mar. Servicio de Hidrografía Naval, Buenos Aires, 1961. -Celemin A. – Manolidis N. Situaciones Meteorológicas Generadoras de Oleaje Gran Altura y de Crecientes Extraordinarias del mar en la Zona de Mar del Plata. Meteorológica Vol XIV. N 1y 2 1983. - Celemin, A., 1984: Meteorología práctica. Edición del autor. Mar del Plata. Argentina. 153 pag. -Ciappesoni H- Salio Paula: Pronóstico de Sudestada en el Río de la Plata. Meteorológica Vol. 22 ,N - .1997 - Green, P. E. & Carol. 1978. Analysing Multivariate Data. The Dryden Press. Illinois, U.S.A, 519 pp. - Jussem J. C.y Atlas R., 1991: Diagnostic evaluation of the numerical model simulations using the tendency equation. Mon. Wea. Rev., Vol. 199, N° 12, 2936-2954. - Necco, G., 1982 a: Comportamiento de los vórtices ciclónicos en el área sudamericana durante el FGGE: ciclogénesis. Meteorológica, Vol. XIII, N° 1, 7-20. - Necco, G., 1982 b: Comportamiento de los vórtices ciclónicos en el área sudamericana durante el FGGE: trayectoria y desarrollos. Meteorológica, Vol XIII, N° 1, 21-34. - Rivero O. R. y Bischoff S., 1971: Ciclogénesis, movimiento y distribución de depresiones en los Océanos Atlántico y Pacífico Sur durante el período abril 1967-mayo 1968. Meteorológica, Vol 1,2 y 3, 476-523. Schwerdtfeger, W., 1954: Análisis sinóptico y aspectos climatológicos de dos distintos tipos de depresiones báricas en el norte de Argentina. Meteoros, Vol 4, 301-323. Seluchi M., 1995: Diagnóstico y pronóstico de situaciones sinópticas conducentes a desarrollos ciclónicos sobre el este de Sudamérica. Geofísica Internacional, Vol 34, 171-186.
18
-30
-31
-32
-33
-34 RIACHUELO DOCK F -35 RIO DE LA PLATA
-36
-37
-38
-60 -59 -58 -57 -56 -55 -54 -53 -52 -51
Figure 1: Geographical location of Riachuelo Dock F.
ANNUAL DISTRIBUTION OF SUDESTADAS IN THE RIO DE LA PLATA STORM SURGE OVER 1.60M 35
30
25
20
15
FREQUENCY 10
5
0 Expected E F M A M J J A S O N D Normal MONTHS
Figure 2: Annual distribution of sudestadas in the Rio de la Plata. Storm surge over 1.60m.
19
DECADAL DISTRIBUTION SUDESTADAS IN THE RIO DE LA PLATA STORM SURGE OVER 1.60 M 90 80 70 60 50 40 30 FREQUENCY 20 10 0 1950 1960 1970 1980 1990 2000 YEARS
Figure 3: Decadal distribution of sudestadas in the Rio de la Plata.
STORM SURGE HEIGHT 140 130 120 110 100 90 80 70 60 50 FREQUENCY 40 30 20 10 0 140 160 180 200 220 240 260 280 300 320 340 360 CENTIMETERS
Figure 4: Distribution of storm surge height (cm).
20
SUDESTADA DURATION 180
160
140
120
100
80
FREQUENCY 60
40
20
0 0 20 40 60 80 100 120 140 160 180 HOURS
Figure 5: Distribution of sudestadas duration (hours).
ANNUAL DISTRIBUTION OF SUDESTADAS IN THE RIO DE LA PLATA STORM SURGE OVER 2.05 M 10 9 8 7 6 5 4
FREQUENCY 3 2 1 0 Expected E F M A M J J A S O N S Normal MONTHS
Figure 6: Annual distribution of sudestadas in the Rio de la Plata. Stor surge over 2.05m.
21
DECADAL DISTRIBUTION OF SUDESTADAS IN THE RIO DE LA PLATA STORM SURGE OVER 2.05M 22 20 18 16 14 12 10 8
FREQUENCY 6 4 2 0 1950 1960 1970 1980 1990 2000 YEARS
Figure 7: Decadal distribution of sudestadas in the Rio de la Plata.
22
MEAN GEOPOTENTIAL HEIGHT AT 1000 hPa - DAY 0 / 00 U.T.C. -20
-30
-40
-50
-60 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40
MEAN GEOPOTENTIAL HEIGHT AT 1000 hPa - DAY 0 / 12 U.T.C. -20
-30
-40
-50
-60 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40
MEAN GEOPOTENTIAL HEIGHT AT 1000 hPa - DAY 1 / 00 U.T.C. -20
-30
-40
-50
-60 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40
Figure 8: Average sequence of the 1000 hPa height fields associated to sudestada events.
23 MEAN GEOPOTENTIAL HEIGHT - 1951 / 2000 MEAN GEOPOTENTIAL HEIGHT AT 1000 hPa - 1951 / 1960 -20 -20
-25 -25
-30 -30
-35 -35
-40 -40
-45 -45
-50 -50
-55 -55
-60 -60 -80 -75 -70 -65 -60 -55 -50 -45 -40 -80 -75 -70 -65 -60 -55 -50 -45 -40
MEAN GEOPOTENTIAL HEIGHT AT 1000 hPa - 1961 / 1970MEAN GEOPOTENTIAL HEIGHT AT 1000 hPa - 1971 / 1980 -20 -20
-25 -25
-30 -30
-35 -35
-40 -40
-45 -45
-50 -50
-55 -55
-60 -60 -80 -75 -70 -65 -60 -55 -50 -45 -40 -80 -75 -70 -65 -60 -55 -50 -45 -40 MEAN GEOPOTENTIAL HEIGHT AT 1000 hPa - 1981 / 1990MEAN GEOPOTENTIAL HEIGHT AT 1000 hPa - 1991 / 2000 -20 -20
-25 -25
-30 -30
-35 -35
-40 -40
-45 -45
-50 -50
-55 -55
-60 -60 -80 -75 -70 -65 -60 -55 -50 -45 -40 -80 -75 -70 -65 -60 -55 -50 -45 -40
Figure 9: Mean 1000 hPa geopotential height fields associated to sudestadas. a) average for 51/00, b) average for 51/60, c) average for 61/70, d) average for 71/80, e) average for 81/90, f) average for 91/00.
24 1 CPs - 33,4 % 1 CPs - COMPOSITES (Storm Surge > 160 cm) -20 -20
-25 -25
-30 -30
-35 -35
-40 -40
-45 -45
-50 -50
-55 -55
-60 -60 -80 -75 -70 -65 -60 -55 -50 -45 -40 -80 -75 -70 -65 -60 -55 -50 -45 -40
2 CPs - 29,2 % 2 CPs - COMPOSITES (Storm Surge > 160 cm) -20 -20
-25 -25
-30 -30
-35 -35
-40 -40
-45 -45
-50 -50
-55 -55
-60 -60 -80 -75 -70 -65 -60 -55 -50 -45 -40 -80 -75 -70 -65 -60 -55 -50 -45 -40
3 CPs - 13 % 3 CPs - COMPOSITES (Storm Surge > 160 cm) -20 -20
-25 -25
-30 -30
-35 -35
-40 -40
-45 -45
-50 -50
-55 -55
-60 -60 -80 -75 -70 -65 -60 -55 -50 -45 -40 -80 -75 -70 -65 -60 -55 -50 -45 -40
Figure 10: Principal Components (PCs) (left) and composite 1000 hPa height fields (right).
25 FACTOR LOADING 1 - STORM SURGES > 160 cm
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1
CORRELACION 0 -0.1 -0.2 -0.3 -0.4 -0.5 FL1 -0.6
H130251 H310552 H040753 H010955 H090558 H160459 H071060 H270461 H090862 H170967 H230869 H300672 H180474 H210276 H160577 H030479 H140980 H160781 H260482 H100283 H160484 H170186 H100187 H240989 H071190 H270592 H210493 H010394 H200495 H200497 H020298 H131298 H291099 FECHAS
FACTOR LOADING 2 - STORM SURGES > 160 cm
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 FL2 0.1
CORRELACION 0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 H130251 H310552 H040753 H010955 H090558 H160459 H071060 H270461 H090862 H170967 H230869 H300672 H180474 H210276 H160577 H030479 H140980 H160781 H260482 H100283 H160484 H170186 H100187 H240989 H071190 H270592 H210493 H010394 H200495 H200497 H020298 H131298 H291099 FECHAS
FACTOR LOADING 3 - STORM SURGES > 160 cm
1 0.9 0.8 0.7
0.6 0.5 0.4 0.3 0.2 0.1
CORRELACION 0 -0.1 -0.2
-0.3 -0.4 -0.5 FL3 -0.6 H130251 H310552 H040753 H010955 H090558 H160459 H071060 H270461 H090862 H170967 H230869 H300672 H180474 H210276 H160577 H030479 H140980 H160781 H260482 H100283 H160484 H170186 H100187 H240989 H071190 H270592 H210493 H010394 H200495 H200497 H020298 H131298 H291099 FECHAS
Figure 11: Series of factor Loading for each component.
26 ANNUAL DISTRIBUTION - STORM SURGES > 160 cm 1 CPs 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3
NUMBER OF OBSERVATIONS 2 1 0 E F M A M J J A S O N D MONTHS
ANNUAL DISTRIBUTION - STORM SURGES > 160 cm 2 CPs 14 13 12 11 10 9 8 7 6 5 4 3 2 NUMBER OF OBSERVATIONS 1 0 E F M A M J J A S O N D MONTHS
ANNUAL DISTRIBUTION - STORM SURGES > 160 cm CPs 3 6
5
4
3
2
1 NUMBER OF OBSERVATIONS 0 E F M A M J J A S O N D MONTHS Figure 12: Annual distribution of sudestadas. Mode 1 (above), Mode 2 (center) and Mode 3 (below).
27
J F M A M J J A S O N D N 178 167 149 152 187 148 133 133 125 170 160 190 NE 140 132 123 124 69 68 110 98 123 113 132 150 E 241 238 189 143 100 89 136 205 225 204 217 222 SE 131 124 120 97 106 92 126 142 151 102 121 146 S 107 140 154 151 124 143 152 146 146 142 143 100 SW 51 58 72 85 116 113 93 62 66 86 55 38 W 54 50 73 103 126 138 93 80 54 63 60 45 NW 44 44 67 53 114 115 77 48 51 57 68 55 CALM 54 47 53 92 58 94 80 86 59 63 44 54
Table I: Monthly winds frequency at Aeroparque station (j= 34°34’S, l=58°25’W). Period 1981/1990.
28 PC 1 VARIABLE N MEAN MINIMU MAXIMU M M HEIGH 107 253. 202 403 0 STORM 107 189. 161 348 SURGE 6 ASTRON. 107 63.3 29 148 WAVE DURATION 107 40.2 25 113 PC 2 VARIABLE N MEAN MINIMU MAXIMU M M HEIGHT 85 251.0 202 366 STORM 85 189.0 161 295 SURGE ASTRON.WA 85 62 31 110 VE DURATION 85 50.9 25 175 PC 3 VARIABLE N MEAN MINIMU MAXIMU M M HEIGHT 18 285. 215 350 1 STORM 18 226. 164 304 URGE 1 ASTRON. 18 58.9 32 91 WAVE DURATION 18 70.1 37 108
Table II: Statistical parameters of the variables analyzed for each of the three PCs (PC1 above, PC2 center, PC3 below).
29
ANNEX TASK 21
The greatest discharge events in the Paraná River and their climate forcing
Inés A. Camilloni Department of Atmospheric and Ocean Sciences, University of Buenos Aires/ CIMA-CONICET Buenos Aires, Argentina Fax 54 11 4576 3356/3364 ext. 12 e-mail: [email protected]
and
Vicente R. Barros Department of Atmospheric and Ocean Sciences, University of Buenos Aires/ CONICET Buenos Aires, Argentina Fax 54 11 4576 3356/3364 ext. 12 e-mail:[email protected]
April 2002
REVISED: November 2002
Corresponding author: Inés Camilloni Ciudad Universitaria. Pabellón II. 2do Piso.
30 1428. Capital Federal Tel. 55 11 4576 3356/3364 ext. 28 Fax 55 11 4576 3356/3364 ext. 12 e-mail: [email protected]
31 Abstract
The greatest monthly discharge anomalies of the Upper Paraná of the 1904-1998 period were examined with focus on the contribution from the sub-basins and the climate forcing of these events. The major discharge anomalies in Corrientes originated in the central Upper Paraná basin.
The contributions from the Paraguay and the northern Upper Paraná rivers to these anomalies were relatively small.
About two thirds of the major discharge anomalies in Corrientes occurred during El Niño events, and none of these major anomalies took place during La Niña events. The major discharge anomalies that were related to El Niño occurred either in the spring of the year of El
Niño onset or in the autumn of the following year (autumn (+)) accompanying the precipitation signal of El Niño in eastern subtropical South America. The top discharges of the Paraná River at
Corrientes occurred in the autumn (+) whenever El Niño SST anomaly in El Niño 3 region persisted until this season. The remaining third of the major discharge that were not related to El
Niño, took place during the austral spring or the austral summer of neutral periods. In each season, they share a common SST anomaly pattern in the proximity of the South American coasts.
Key words: flood; El Niño; Paraná; river discharge
32 1. Introduction
The Paraná River is the most important tributary of the Río de la Plata estuary, contributing with more than 85 % of the Río de la Plata streamflow. It begins at the confluence of the Grande and Paranaíba rivers and its main tributaries are the Paranápanema, Iguazú and Paraguay rivers
(Fig. 1). Its drainage basin covers 2.6 x 106 km2. Upstream from the confluence with the
Paraguay at Corrientes, the river is known as the Upper Paraná, and downstream from this place as the Middle Paraná up to 32°S. From this point on is called Lower Paraná. The Upper Paraná flows mostly in areas with steep terrain that favors the runoff (Tossini 1959). On the other hand, the Middle and Lower Paraná flow in a gently sloping plain up to the river outlet at the Río de la
Plata. The last sector of the river becomes a delta and together with the Uruguay River forms the estuary of the Río de la Plata.
The mean discharge of the Upper Paraná is about 16,000 m3/s and only increases less than
1,000 m3/s downstream from Corrientes (Argentine Secretariat of Energy 1994). During the greatest floods, monthly discharges at Corrientes exceed twice, and even three times, this value.
On the other hand, the contributions from the Middle and Lower Paraná basins to the great discharges are relatively small (data available through the National Department of Water
Resources website http://www.mecon.gov.ar/hidricos/mapashidricos/mapageneral.htm). The only important exception was during 1998 when the Middle Paraná had an important contribution from the extraordinary April rainfall.
Large areas of land along the margins of the Middle and Lower Paraná are subject to severe floods. A better understanding of the atmospheric forcing of these floods can help prevent future disasters such as those of 1983 and 1998. In 1983 more than 100,000 people were evacuated
(Anderson et al. 1993) and losses amounted to more than one billion American dollars.
Most of the literature about the Paraná streamflows has dealt with statistical analysis of discharges, remote climate forcing or descriptions of individual events. For instance, García and
33 Vargas (1996, 1998) and Genta et al (1998) have identified a positive trend in the Paraná discharges and its tributaries since 1976, and Mechoso and Robertson (1998) analyzed decadal teleconnections between sea surface temperature (SST) and the Paraguay and Paraná streamflows. There are also consistent evidences of the link between the Paraná discharge and the
El Niño-Southern Oscillation (ENSO). For example, Aceituno (1988) found a weak negative correlation between discharges at Corrientes and the southern oscillation index (SOI) during
November-April, and Amarasekera et al (1997) reported a positive correlation between the annual discharge at Corrientes and the equatorial Pacific SST averaged on quarters lagging ahead of the discharge year. Depetris et al (1996) reported a significant coherence-square between SST at the equatorial Pacific and discharge at Corrientes in the neighborhood of the 2.5 years period.
They reported the extraordinary magnitude of the 1982/83 flood, which coincided with the strong
El Niño event of 1982, and commented that four other large floods also occurred in coincidence with El Niño events. Camilloni and Barros (2000) studied the river response to El Niño 1982-83 and 1997-98 events.
Despite the aforementioned contributions, a complete description of the greater flood features and its causes is still lacking. Therefore, this article focuses on the contribution from the sub- basins upstream from Corrientes to the major discharges of the Paraná, and on the possible climate forcings of these events. The major discharges in the Middle and Lower Paraná themselves are not part of this study due to the lack of long-term series at stations downstream from Corrientes. However, since the Middle and Lower Paraná discharges are mostly determined, with some lag, by the Upper Paraná discharge, the conclusions are also useful for the understanding of floods in these sectors of the river.
The paper is organized as follows. Hydrological and meteorological data are described in section 2. Section 3 examines the greatest discharge anomalies that have occurred during the last century while the climatic forcings associated to these events are discussed in section 4. Section 5
34 discusses the hydrological response to the extraordinary 1982-83 El Niño event and conclusions are summarized in section 6.
2. Data
The study is based on monthly discharges at 5 gauging stations. This allows the estimate of contributions of some sub-basins to the Upper Paraná River discharge (Fig, 1). Table 1 shows their record periods and mean annual discharges.
Discharges at the Brazilian gauging stations of Jupiá, Itaipú and Salto Caxias were obtained from the Brazilian National Operator of the Electric System (BNONS). Because dams on the
Upper Paraná and on the Iguazú River have modified the natural flow of these rivers, especially after 1980, the discharge data provided by the BNONS was unregulated. Data from the Argentine stations of Corrientes and Puerto Bermejo were taken from the National Department of Water
Resources (NDWR). Puerto Bermejo discharges do not require corrections because there are no dams on the Paraguay River. On the other hand, dams upstream from Itaipú affect Corrientes streamflow. The comparison between the regulated and the natural monthly flows at Itaipú indicates that the regulation upstream from this location has varied from -7,000 m3/s to +4,600 m3/s, being negative in summer and positive in winter and spring. However, in the case of the great positive discharge anomalies, these differences were smaller. They were about 5% -or even less- of the Corrientes discharge anomalies, with only one exception that reached nearly 10%.
Downstream from Itaipú, the great dams of Itaipú and Yaciretá do not introduce important alterations in the river flow.
Monthly rainfall series were taken from a data set assembled by Willmott and Matsura (2001).
These data are available in a 0.5º x 0.5º grid for the period 1950-99. The relation between sea surface temperature (SST) and river discharges was studied using the monthly SST data set
GISST version 2.3b obtained from the British Atmospheric Data Center (BADC 2002).
35 El Niño and La Niña periods that occurred after 1950 were determined in accordance with the
ENSO events listed by Trenberth (1997). ENSO events before 1950 were determined according to Kiladis and Diaz (1989).
3. Major discharge events
Table 2 shows the greatest discharge anomalies at Corrientes calculated with respect to the
1931-80 monthly means. The sixteen events listed correspond to the period 1904-2000, and they were selected following the criterion that the discharge anomalies were at least three times the standard deviation of the respective month. If two consecutive months met this requirement, only the one with the greatest anomaly was retained. Hereinafter, these discharge anomalies will be referred to as the major discharge anomalies. The magnitude of these extraordinary discharges at
Corrientes minimizes the possible impact of water management by upstream dams.
The cases listed in Table 2 constitute events that must necessarily have been caused by considerable monthly precipitation anomalies over a large area of the upstream basin. Because of their size and time scale, these precipitation anomalies could be likely linked to a common large- scale climate forcing. To facilitate the discussion of this aspect, Table 2 includes a classification of the events according to the season and the phase of El Niño-Southern Oscillation (ENSO).
The monthly discharge anomalies at the gauging stations of Jupiá and Puerto Bermejo represent respectively the northern Upper Paraná and the Paraguay discharges. In the case of
Jupiá, the discharge anomalies corresponding to the month previous to the event in Corrientes were also included due to the possibility of a zero to one-month lag in the streamflows between these stations (Camilloni and Barros 2000). Table 2 also shows the contribution from the basin corresponding to the central sector of Upper Paraná and of the Iguazú rivers, calculated by subtracting the discharges at Jupiá from the sum of the discharges at the gauging stations of Salto
Caxias and Itaipú. The corresponding basin will hereinafter be referred to as the central Upper
36 Paraná basin. Similarly, the difference between the Corrientes discharges and discharges at
Itaipú, Puerto Caxias and Puerto Bermejo represents the contribution from the Upper Paraná basin between the confluence of the Iguazú and Paraguay rivers with the Paraná. Its respective basin will be addressed in this paper as the southern Upper Paraná basin. Regulated discharges at
Itaipú were used in this latter case because dams upstream from Itaipú regulate Corrientes discharges.
It cannot be expected an accurate quantitative balance between the discharges and the upstream contributions shown in Table 2. Even assuming that all of the discharges were carried on downstream, it is impossible to achieve an accurate balance at monthly scale, because the discharge propagation cannot be correctly captured with a one-month time resolution. In addition, the lag time between rainfall in the different sub-basins and the discharge response at the gauging stations at their outlet spreads from less than a month to one or more months (Camilloni and
Barros 2000). Therefore, Table 2 allows the assessment of only the bulk magnitude from the sub- basin contributions to every major discharge event in Corrientes.
The greatest contributions to the major discharge anomalies in Corrientes came from the central and southern Upper Paraná basins, especially from the latter. In general, these contributions constituted about two thirds or more of the discharge anomaly in Corrientes. The only cases with important contributions from the northern Upper Paraná occurred during the extraordinary El Niño 1982-1983 or a few months after its end. Though always positive, the discharge anomalies in Puerto Bermejo were considerably smaller than those of the Upper
Paraná. Thus, the contribution from the Paraguay River to the major discharge anomalies in
Corrientes adds to the contribution from the Upper Paraná, although in a relatively low proportion. The negligible impact from the northern Upper Paraná on the major discharges at
Corrientes is peculiar, considering that the northern Upper Paraná contributes with almost 40% of
37 the annual mean discharge at Corrientes, and with little less than 50% of the Upper Paraná discharge.
Since with few exceptions, the major discharge events in Corrientes originate in the central and southern Upper Paraná basin, and especially in the last one, Table 3 presents the major anomaly contributions corresponding to this part of the basin [Itaipú + Salto Caxias - Jupiá] for the period 1931-98. The table includes a classification of these events according to the season and the phase of the ENSO. The 18 events listed are those whose anomalies were greater than at least three times the standard deviation for the respective month. As in the case of the Corrientes discharges, the greatest anomaly was registered in June 1983, but the rest of the events are not equally ranked as in the Corrientes case (Tables 2 and 3). However, there is a good correspondence between the great discharge anomalies in Corrientes and the anomalies in discharge contributions shown in Table 3. The contributions from the northern Upper Paraná to the major discharge anomalies in the central Upper Paraná are generally small -less than 25 %- or even negative, except for a few cases during 1982 and 1983 (Table 3). The correlation between monthly discharge contributions from the northern and central Upper Paraná is also small, only 0.25, indicating a weak relation between precipitation over these two neighboring basins.
4. Climatic forcing of the major discharge anomalies
4.1 The annual cycle
The rainfall regime in the Upper Paraná basin changes from a pronounced annual cycle in the north to a less defined cycle over the Iguazú, southern Upper Paraná and Lower Paraguay basins
(Camilloni and Barros 2000; Grimm et al. 2000). Over this region, the impact of the South
Atlantic convergence zone (SACZ) in summer is smaller than it is in the northern Paraná basin, and during winter and spring there is an important frequency of cyclogenesis (Gan and Rao 1991;
Rao et al 1996). In the Pantanal, rainfall presents a very pronounced annual cycle with a maximum in summer. However, due to the extreme flatness of this region and the small runoff associated thereto, this maximum appears with a delay of 5-8 months in the streamflow of Puerto
Bermejo (Camilloni and Barros 2000). As a result of this, the river discharge at Corrientes has an attenuated annual cycle, but even so, during the 1931-1980 period it showed a maximum of around 21,000 m3/s during February and March of and a minimum of 12,000 m3/s during August and September.
38 In spite of this well-marked annual cycle in the streamflow, the frequency of occurrence of the major discharge anomalies at Corrientes was higher in autumn and spring (Table 2). This is a consequence of the seasonal variation of the precipitation response to El Niño in the Paraná basin
(Grimm et al 2000) and the link between most of these anomalies and El Niño. This was also observed in the central Upper Paraná, where only 3 of the 18 major contributions to discharge anomalies correspond to the December-February period (Table 3).
4.2 ENSO relationship
There is a clear relationship between ENSO phases and the major discharge anomalies in the
Paraná River. In Corrientes, 11 out of 16 occurred during El Niño events (Table 2). In addition, none of them occurred during La Niña phase. In the case of the major contributions from the central Upper Paraná, the proportion during El Niño phase was about the same, namely, two thirds (Table 3). In the northern Upper Paraná, this proportion was lower, as only 6 of the 13 major discharge anomalies occurred during El Niño phase. In addition, there were no major discharge anomalies during La Niña phases in any of the three basins.
The hydrological response to ENSO may seem obvious, as the Paraná basin is part of a region that has a strong precipitation signal during ENSO events (Kousky et al 1984, Ropelewski and
Halpert 1987, 1996; Kiladis and Díaz 1989). However, this response varies along each ENSO phase, (Grimm et al 2000) and the monthly or seasonal correlation between the SOI and the
Paraná discharge is relatively weak (Aceituno 1988). On the other hand, the link between ENSO and the major discharge anomalies in Corrientes is more explicit (Table 2).
4.2.1 El Niño austral autumn
The top discharges of the Paraná River at Corrientes occurred during the austral autumn
(March to June) of the year following the onset of an El Niño event (autumn (+)). In all five of
39 the top-six major discharge anomalies that were simultaneous with the El Niño events of 1904-
05, 1982-83, 1991-92 and 1997-98, El Niño SST anomaly in El Niño 3 region (greater than
0.5°C) continued until May. In the other three El Niño events of the twentieth century in which El
Niño SST anomalies continued until the autumn (+) in El Niño 3 region, there were also important positive discharge anomalies in Corrientes. They occurred in March 1926 with 10,500 m3/s; in May 1930, with 11,600 m3/s; and in June 1987, with 10,900 m3/s. In addition, Camilloni and Barros (2000) showed that there is a significant (95% level) Spearman rank correlation (0.69) between El Niño 3 SST and Corrientes discharge during autumn (+) when all twenty-century El
Niño events are considered. Summarizing, during the twentieth century there was a great positive discharge anomaly at the outlet of the Upper Paraná. whenever El Niño 3 SST anomalies remained greater than 0.5°C until the autumn (+).
The anomalous circulation of ENSO events over the western Southern Hemisphere during the winter was attributed to stationary Rossby wave propagation forced by the anomalous equatorial warming in the Central Pacific (Karoly 1989). An analogous wave propagation was described by
Barros and Silvestri (2002) for the spring, and it could possible be similar in autumn (+). During this season, the anomalous circulation increases the advection of cyclonic vorticity in the upper troposphere and the advection of warm and humid air at low levels, enhancing the precipitation over the central and southern Upper Paraná (Grimm et al. 2000)
As result of these conditions, precipitation during the autumn (+) season is important over the central and southern Upper Paraná and lower Paraguay basins. Figure 2 presents the composite of rainfall anomalies for the March-May quarter corresponding to years when positive SST anomalies, over 0.5°C, persisted in El Niño 3 region until May. According to this figure, there is little chance that this teleconnection might influence the Upper Paraná discharges. In fact, none of the major discharges at Jupiá took place in autumn (+)
.
40 4.2.2 El Niño austral spring
Five of the peaks that rank among the major streamflow contributions from the central Upper
Paraná occurred in spring during El Niño phase (Table 3). This is in agreement with the general behavior of this streamflow contribution during the spring of the years of El Niño onset (spring
(0)). In fact, these contributions presented small negative anomalies only in two out of 18 El Niño events that occurred during the 1931-98 period, and in 10 cases their anomalies were considerably positive, ranging from 2,500 m3/s to 10,300 m3/s.
As in the case of the autumn (+), the greatest anomalies in the composite rainfall for the spring
(0) are in the Upper Paraná basin, but with the maximum centered 300 km to the south with respect to the autumn (+) (Fig. 3). This anomaly field is consistent with the increment of the cyclonic vorticity advection in the upper troposphere (Barros and Silvestri 2002) and with the enhancement of the subtropical jet over South America (Grimm et al. 1998) during the spring (0).
At this time of the year, the baroclinicity over subtropical South America is important, and its enhancement during El Niño years favors the already frequent cyclogenesis and the development of mesoscale systems (Gan and Rao 1991; Velasco and Fritsh 1987).
4.3 Other climatic forcings
One out of three of the major discharge anomalies took place during the austral spring
(September to November) or during the austral summer (December to February) of neutral periods and therefore, they were not forced by ENSO events. For their study, we will focus on the central Upper Paraná, where the neutral cases rank higher among the major discharge contributions than in the case of Corrientes (Table 3).
4.3.1 Neutral austral summer
41 The discharge contribution of the central Upper Paraná is significantly correlated at a 90 % level with January-February SST over most of the subtropical South Atlantic (Fig. 4). This is particularly true west of 20°W, a region where SST is related to low-level circulation and precipitation over subtropical South America during midsummer (Doyle and Barros 2002).
Another area of significant positive correlation is that of El Niño 1+2. However, there is no significant correlation with SST in the rest of El Niño regions, which is consistent with the lack of ENSO signal during midsummer. As a matter of fact, while precipitation has a strong ENSO signal in eastern subtropical South America during the spring (0) and autumn (+), this signal vanishes during January-February (Grimm 2000).
In view of the lack of El Niño signal in the midsummer precipitation in subtropical South
America, other climate forcing could have caused the peak discharge of January 1995 (El Niño month). Therefore, this case is discussed together with the two neutral cases. Actually, SST anomalies in the three summers with major discharge contributions in the central Upper Paraná share common features. They show positive anomalies along the Pacific coast of South America from the Equator to 30°S, as well as in the subtropical Atlantic west of 20°W. These features are consistent with the correlation pattern shown in Fig. 4, which favors the positive anomalies in the discharge contributions of the central Upper Paraná during summer.
4.3.2 Neutral austral spring
. When only neutral springs are considered, the discharge contribution from the central Upper
Paraná is negatively and significantly correlated at a 90 % level with September-October SSTs in both oceans near the coasts of South America, south of 20°S (Fig. 5). Over the eastern tropical
Pacific, positive significant correlations predominate to the south of the equator.
The SST anomalies corresponding to the four cases of the major discharge contribution in the central Upper Paraná are shown in Fig. 6. October 1935 and September 1990 present cold
42 anomalies off the coast of South America in both oceans, in accordance with the correlation pattern (Fig 6a and 6c). In the case of September 1989, the pattern in these regions is similar, although the anomalies are smaller (Fig 6b). Thus these features, which according to the correlation pattern (Fig. 5) favor positive discharge anomalies, have been associated to the major anomalies in the central Upper Paraná contribution. The anomaly pattern over the eastern tropical and subtropical Pacific of October 1998 was consistent with the correlation pattern (Fig. 6d) that indicates that warm anomalies in the tropical eastern Pacific south of the equator are predominantly associated with greater than normal precipitation over the Upper Paraná basin.
5. The extraordinary 1982-83 event
The impact of the strong El Niño 1982-83 event in the Paraná streamflow was the greatest recorded. The river anomaly discharge in Corrientes exceeded 10,000 m3/s from July 1982 to
December 1983 (Camilloni and Barros 2000). In that period occurred five out of the 16 major discharge anomalies, i.e. in July and December 1982 and in March, June and October 1983
(Table 2). In June 1983 was registered the greatest monthly discharge of the record initiated in
1904. The spatial extension of this impact was also exceptional, reaching the northern Upper
Paraná, where 3 out of the 13 major discharges occurred during 1982-83 including the top one registered in February 1983.
The peaks of March and June 1983 occurred during the autumn (+) of El Niño phase. During
June 1983, the magnitude of the SST positive anomaly at El Niño 3 region was the highest of the entire record, and it was considerably higher than in the average for El Niño events (Fig. 7).
Therefore, according to the Spearman rank correlation (0.69), this peak should be expected to be the highest among the autumn (+) discharges in Corrientes, as it actually is (Table 2).
The peak of December 1982 originated in November 1982 in the upper Middle Paraná basin, but it received contributions from the other basins, including the central Upper Paraná basin. This
43 case fits into the category of the spring (0) events that were associated with large positive discharge anomalies.
Other factors must have been influencing the extraordinary precipitation during the austral winter of 1982, because in other El Niño cases with greater SST anomalies in winter (0) the discharge response was smaller. Considering only the months when El Niño had already started, the rainfall anomalies during winter (0) were positive over the northern Upper Paraná basin (Fig.
8). This feature coincides with the 1982 case (Table 2). However, in half of El Niño cases that took place during the 1951-1998 period, the SST positive anomaly in El Niño 3 region during the austral winter (0) was equal to or greater than in the 1982 event. For instance, in the case of the
1997 event, the positive anomaly in the discharge contribution from the central Upper Paraná was only of 6,300 m3/s in July, contrasting with the 9,200 m3/s of 1982, although the respective SST at El Niño 3 region was almost 2º C higher than in 1982.
In the case of the October 1983 peak, the anomalous SST at El Niño 1+2 region was still extremely high (1.5º C) after the end of the El Niño episode (Fig. 9). For neutral springs, the correlation between the central Upper Paraná discharge contribution and SST at El Niño 1+2 region is significant and positive (Fig. 5). However, in October 1983, the contribution to the major discharge in Corrientes came also from the Upper Paraná and the southern Upper Paraná basin indicating that, as in winter (0), other climatic factors could be responsible for the great hydrological response of the Paraná River.
Although the conjunction of different factors could have contributed to the anomalous precipitation in the Paraná basin during the 1982-1983 period, the exceptional magnitude of these anomalies, and particularly their extension and persistence before, during, and after El Niño event require an additional and more comprehensive explanation.
6. Conclusions
44 Although the contribution from the central and southern Upper Paraná is only about 40% of the Corrientes mean discharge, the major discharges in Corrientes usually originated in these basins, especially in the central Upper Paraná. The contribution from the Paraguay River enhances the Upper Paraná major discharges, but in a relatively small proportion. On the other hand, the contribution from the northern Upper Paraná to the major discharge anomalies in
Corrientes is, not only generally small, but it is even negative in some cases.
There is a clear relationship between the phases of ENSO and the major discharge anomalies in the Upper Paraná. About two thirds of the major discharge anomalies in Corrientes and of the major anomalous contributions from the central Upper Paraná occurred during El Niño events. In addition, none of the major anomalies occurred during La Niña phase. This contrasts with the weak monthly or seasonal correlation between the Southern Oscillation index and discharges in
Corrientes, indicating that the major discharge anomalies were more related to El Niño phase than the rest of these anomalies.
The major discharge anomalies in Corrientes and major discharge contributions from the central Upper Paraná that were related to El Niño occurred either in spring (0) or in autumn (+), accompanying the seasonal variation of El Niño precipitation signal in eastern subtropical South
America. During the twentieth century, the top discharges of the Paraná River at Corrientes occurred in the autumn (+). In all of these events, El Niño SST anomaly in El Niño 3 region persisted until May (+) and also, whenever El Niño 3 SST anomalies continued until the autumn
(+), there was an important positive discharge anomaly in the Upper Paraná.
The remaining third of the major discharge contributions from the Upper Paraná took place during the austral spring or the austral summer of neutral periods. During the summer cases, there were positive anomalies along the Pacific coast of South America from the Equator to 30°S, as well as predominant positive anomalies in the subtropical Atlantic west of 20°W. During the neutral springs, the discharge contributions from the upper part of the Upper Paraná have
45 significant negative correlation with the September-October SSTs in both oceans south of 20°S in the proximity of the South American coasts, as well as significant positive correlation over the eastern tropical Pacific. The SST patterns for the neutral spring months with major discharge contributions from the central Upper Paraná were consistent with this correlation pattern, either in the eastern Pacific or near the South American continent, south of 20ºS. However, as in the case of summer, there is no indication that these SST patterns were always accompanied by great anomalies in the discharge contribution from the central Upper Paraná. Thus, the influence from transient components of the atmospheric flow over the precipitation associated with some of the major discharge anomalies cannot be discarded.
The extraordinary El Niño 1982-83 event was accompanied by the greatest monthly discharge registered in Corrientes and by a persistent anomalous high streamflow that went on from July
1982 to December 1983. Although the combination of different factors could have contributed to this long persistence during a year and a half, the exceptional magnitude of these anomalies and their spatial extension require a better understanding.
Acknowledgements
The authors are grateful to the British Atmospheric Data Centre (BADC) for providing access to the GISST dataset. This work was funded by the University of Buenos Aires and by
Assessments of Impacts and Adaptations to Climate Change (AIACC), a GEF/START/TWAS
Project.
References Aceituno, P., 1988. On the functioning of the Southern Oscillation in the South American sector.
Part I: Surface climate. Mon. Wea. Rev. 116, 505-524.
Amarasekera, K.N., Lee, R., Williams, E.R., Eltahir, E.A.B. 1997: ENSO and natural variability in the flow of tropical rivers. J. Hydrology 200, 24-39.
46 Anderson, R.J., Ribeiro dos Santos N.D., Diaz, H. F., 1993. An analysis of flooding in the
Paraná/Paraguay River basin. LATEN Dissemination Note #5, World Bank.
Argentine Secretariat of Energy, 1994. Estadística Hidrológica (Hydrological Statistics), 651 pp.
BADC, 2002. British Atmospheric Data Centre. Global ocean surface temperature (GISST) version 2.3b. (Available with restrictions from http://www.badc.rl.ac.uk/data/gisst/).
Barros, V., Silvestri. G.E., 2002. The relation between sea surface temperature at the subtropical south-central Pacific and precipitation in southeastern South America. J.Climate 15, 251-267.
Camilloni, I., Barros, V., 2000. The Paraná River response to El Niño 1982-83 and 1997-98 events. Journal of Hydrometeorology 1, 412-430.
Depetris, P.J., Kempe, S., Latif, M., Mook, W.G. 1996: ENSO-controlled flooding in the Paraná
River (1904-1901). Naturwissenschaften 83, 127-129.
Doyle, M., Barros, V., 2002: Midsummer low-level circulation and precipitation in subtropical
South America and related sea surface temperatures anomalies in the South Atlantic. J.Climate
15, 3394-3410.
Gan, M.A., Rao, V.B., 1991. Surface cyclogenesis over South America. Mon.Wea.Rev. 119,
1293-1302.
García, N.O., Vargas, W.M., 1996. The spatial variability of runoff and precipitation in the Río de la Plata basin. J. Hydro. Sci. 41 , 279-299.
García, N.O., Vargas, W.M., 1998. The temporal climatic variability in the 'Río de la Plata' basin displayed by the river discharges. Climatic Change 38 , 359-379.
Genta, J.L., Pérez-Iribarren, G., Mechoso, C.R., 1998. A recent increasing trend in the streamflow of rivers in Southeastern South America. J. Climate 11, 2858-2862.
Grimm, A.M., Ferraz, S.E.T., Gomes, J., 1998. Precipitation anomalies in Southern Brazil associated with El Niño and La Niña events. J. Climate 11, 2863-2880.
47 Grimm, A.M., Barros, V., Doyle, M., 2000. Climate variability in southern South America associated with El Niño and La Niña events. J. Climate 13, 35-58.
Karoly, D.J., 1989. Southern hemisphere circulation features associated with El Niño-Southern
Oscillation events. J. Climate 2, 1239-1252.
Kiladis, G.N., Diaz, H.F., 1989. Global climatic anomalies associated with extremes in Southern
Oscillation. J. Climate 2, 1069-1090.
Kousky,V.E., Kayano, M.T., Cavalcanti, I. E. A 1984: A review of the Southern Oscillation: oceanic-atmospheric circulation change and related rainfall anomalies. Tellus 36A, 490-504
Mechoso, C.R., Robertson, A.W., 1998. Interannual and decadal cycles in river flows of southeastern South America. J. Climate 11, 2570-2580.
Rao, V.B., Cavalcanti, I.F.A,. Hada, K., 1996. Annual variation of rainfall over Brazil and water vapor characteristics over South America. J. Geophys.Res. 101, D21, 26539-26551.
Ropelewski, C.H., Halpert., S. 1987. Global and regional scale precipitation patterns associated with El Niño/Southern Oscillation. Mon. Wea. Rev. 115, 1600-1626.
Ropelewski, C.H., Halpert, S., 1996. Quantifying Southern Oscillation-precipitation relationships. J. Climate 9, 1043-1059.
Tossini, L., 1959. Sistema hidrográfico y Cuenca del Río de la Plata. Contribución al estudio de su régimen hidrológico. Anales de la Sociedad Científica Argentina, Marzo-abril 1959, III y IV,
Tomo CLXVII, 41-64. (The hydrographic system and the La Plata River basin. A contribution to the study of its hydrological regime. Proceedings of the Argentine Scientific Society, Mar-Apr
1959, III and IV, Vol CLXVII, 41-64)
Trenberth, K.E., 1997. The definition of El Niño. Bull. Amer. Meteor. Soc. 78, 2771-2777.
Velasco, I., Fritsh, J.M. 1987. Mesoscale convective complexes in the Americas. J. Geophys.
Res. 92, D8, 9591-9613.
48 Willmott, C.J., Matsura, K. 2001. Terrestrial air temperature and precipitation: monthly and annual time series (1950-99) Version 1.02. (Available from http://climate.geog.udel.edu/~climate/).
49 FIGURE CAPTIONS
Figure 1. Gauging stations and rivers, 1: Jupiá, 2: Itaipú, 3: Corrientes, 4: Salto Caxias and
5: Puerto Bermejo.
Figure 2. Composite of rainfall anomalies for March (+) to May (+) of El Niño events that persisted until May in El Niño 3 region.
Figure 3. As in Figure 2, but for September to November of El Niño (0) years.
Figure 4. January-February field of the linear correlation between the central Upper Paraná discharge and SST. Significant correlation coefficients at the 90% level are shaded.
Figure 5. As in Figure 4, but for September-October of neutral years.
Figure 6. SST anomalies for (a) October 1935, (b) September 1989, (c) September 1990 and (d)
October 1998.
Figure 7. SST anomalies in El Niño 3 region for the 1982-83 event and for the average of the twentieth century El Niño events.
Figure 8. As Figure 2, but for June to August of El Niño (0) years.
Figure 9. As in Figure 7, but for SST anomalies in El Niño 1+2 region.
50
15S-15.0
r BOLIVIA e iv Paranaiba River R
y a u Grande River -20.0 g 1 20S a r a r P ve
e i R d PARAGUAY á u n t BRAZIL i ra t a a P l Iguazú River 25S-25.0 2 5 4
ARGENTINA 3
30S-30.0
Atlantic Ocean URUGUAY
35S-35.0 65W-65.0 60W-60.0 55W-55.0 50W-50.0 45W-45.0 40W-40.0
longitude
Figure 1
51
15S-15.0
20S-20.0 e d u t i t a l
25S-25.0
30S-30.0
-60.0 -55.0 -50.0 -45.0 -40.0 60W 55W 50W 45W 40W longitude
Figure 2
52
15S-15.0
20S-20.0 e d u t i t a l
25S-25.0
30S-30.0 -60.0 -55.0 -50.0 -45.0 -40.0 60W 55W 50W 45W 40W longitude
Figure 3
53
e d u t i t a l
longitude
Figure 4
54
e d u t i t a l
longitude
Figure 5
55
a) b) e e d d u u t t i i t t a a l l
longitude longitude
c) d) e e d d u u t t i i t t a a l l
longitude longitude
Figure 6
4 average of El Niño events El Niño 1982-83
3
2
1 SST anomalies (°C) 0
year 0 year + -1 J F M A M J J A S O N D J F M A M J J A S O N D months
Figure 7
15S-15.0
20S-20.0 e d u t i t a l
25S-25.0
30S-30.0 -60.0 -55.0 -50.0 -45.0 -40.0 60W 55W 50W 45W 40W longitude
Figure 8
58
6 average of El Niño events El Niño 1982-83 5
4
3
2
1 SST anomalies (°C)
0
year 0 year + -1 J F M A M J J A S O N D J F M A M J J A S O N D months
Figure 9
59
River Station Source Data period Annual mean discharge 1931- 1980 (103 m3/s)
Paraná Jupiá BNONS 1931-1998 5.9
Paraná Itaipú BNONS 1931-1998 9.1
Paraná Corrientes NDWR 1904-1998 15.9 Iguazú Salto Caxias BNONS 1931-1998 1.2
Paraguay Puerto Bermejo NDWR 1910-1998 3.5
Table 1. Gauging stations shown in Fig. 1. BNOS: Brazilian National Operator of the
Electric System, NDWR: Argentine National Direction of Water Resources.
60
Corrientes Jupiá Central Upper Paraná Southern Upper Puerto Bermejo (Northern Upper contribution Paraná contribution (Paraguay) Discharge peak date Paraná) Jun 1983 (Autumn - N(+)) 38.3 8.5 (5.4) 18.1 (13.3) 6.1 5.6 Jun 1992 (Autumn - N(+) 26.8 0.5 (2.5) 10.5 (13.3) 11.3 4.4 Dec 1982 (Spring/Summer - N(0)) 26.1 4.4 (2.3) 9.4 (9.5) 7.6 4.6 Mar 1983 (Autumn - N(+)) 24.2 8.4 (13.2) 8.8 (3.6) 3.8 3.4 Jun 1905 (Autumn - N(+)) 24.2 N/A (N/A) N/A (N/A) N/A N/A May 1998 (Autumn-N(+)) 23.0 0.4 (-1.0) 9.4 (16.3) 8.6 4.6(*) Oct 1998 (Spring - neutral) 21.0 0.8 (-0.4) 15.2 (12.2) 1.0 4.1(*) Oct 1983 (Spring - neutral) 20.5 5.9 (5.4) 6.4 (7.0) 6.0 2.2 Jul 1982 (Winter - N(0)) 18.8 2.9 (3.7) 9.2 (2.9) 3.6 3.1 Feb 1997 (Summer - neutral) 17.7 0.9 (7.4) 12.8 (-2.0) 2.2 1.8 Sep 1989 (Spring - neutral) 16.7 1.0 (1.1) 8.5 (4.5) 3.8 3.4 Sep 1990 (Spring - neutral) 16.4 0.9 (0.7) 7.9 (5.2) 5.7 1.9 Jan 1912 (Summer – N(+)) 15.9 N/A (N/A) N/A (N/A) N/A N/A Nov 1997 (Spring - N(0)) 15.6 1.1 (0.3) 9.8 (9.2) 1.6 3.1 Jan 1966 (Summer - N(+)) 15.4 3.3 (2.4) 2.6 (3.8) 6.5 3.0 Sep 1957 (Spring - N(0)) 15.0 1.3 (0.9) 10.3 (8.4) 1.3 2.0
Table 2. Maximum discharge anomalies at Corrientes and the corresponding discharge anomalies at Jupiá and Puerto Bermejo and discharge contribution anomalies of two sectors of the Upper Paraná. Previous month discharge or contribution anomaly is indicated in brackets. Values in 103 m3/s. (*) Discharge data for 1995-98 were estimated considering river level data.
Central Upper Paraná contribution Jupiá Itaipú+Salto Caxias
Discharge peak date
Jun 1983 (Autumn N(+)) 18.1 8.5 26.6 Apr 1998 (Autumn N(+)) 16.3 -1.0 15.3 Oct 1998 (Spring – neutral) 15.2 0.8 16.0 May 1992 (Autumn N(+)) 13.3 2.5 15.8 Feb 1997 (Summer – neutral) 12.8 0.9 13.7 Jan 1995 (Summer – N) 11.5 -1.3 10.1 Oct 1935 (Spring- neutral) 11.2 1.4 12.6 Jan 1990 (Summer – neutral) 10.8 3.9 14.7 Sep 1957 (Spring – N (0)) 10.3 1.3 11.7 May 1987 (Autumn N(+)) 10.2 1.4 11.6 Nov 1997 (Spring – N(0)) 9.8 1.1 10.9 Oct 1972 (Spring – N(0)) 9.6 2.6 12.2 Nov 1982 (Spring – N(0)) 9.5 2.3 11.8 Jul 1982 (Winter – N(0)) 9.2 2.9 12.1 Mar 1983 (Autumn N(+)) 8.8 8.4 17.1 Sep 1989 (Spring- neutral) 8.5 1.0 9.5 Sep 1990 (Spring- neutral) 7.9 0.9 8.8 Oct 1993 (Spring – N(0)) 7.8 0.9 8.8
Table 3. Maximum discharge contribution anomalies of the central Upper Paraná and the corresponding discharge anomalies at Jupiá and discharge contribution anomalies at Itaipú + Salto Caixas. Values in 103 m3/s.
62
ANNEX TASK 23
Fig 1 Domain for model RP2000
Fig. 2 Domain for model RPP-2D
63
6500000.00
6400000.00
6300000.00 5.00
6200000.00 1.80
1.60 6100000.00
1.40 6000000.00 1.20
5900000.00 1.00
0.80 5800000.00
0.60 5700000.00 0.40
5600000.00
5500000.00 6100000.00 6300000.00 6500000.00 6700000.00 6900000.00
64 Fig 3 Water level contour lines and velocity field from model RPP-2D
6500000.00
6400000.00
6300000.00 1.50
1.25 6200000.00 1.00
6100000.00 0.75
0.50 6000000.00 0.25
0.00 5900000.00 -0.50
5800000.00 -1.50
-2.50 5700000.00 -3.50
5600000.00
5500000.00 6100000.00 6300000.00 6500000.00 6700000.00 6900000.00
Fig 4. Water level contour lines and velocity field from model RPP-2D
65
Fig 6 POM Model Time 10.15 hrs
66
Fig 7 POM Model.Time 15.98 hrs
67
68
ANNEX TASK 24
Figure 1. Geology of Samborombón Bay.
Figure 2. Geomorphologic map of Samborombón Bay.
Figure 3. Satellital Image of wetlands near General Lavalle Town.
Figure.4 -A) Shoreline in the high Pleistocene, approximately 10m above present sea level. B. Position of the sea during the Holocene regression-transgression, 5m above present sea level. C. Position of the sea during Holocene regression. 2.5m above present sea level. 3,500 years BP. D. Present shoreline and coastal dynamics.
ANNEX TASK 25
TABLE 1 – AREA OF DIRECTLY AFFECTED POPULATION, AREA AND DENSITY OF POLITICAL-ADMINISTRATIVE UNITS Total Total Population Political- Area Population Population density for Administrative In sq. km for 1991 CNPyV 2001 CNPyV 2001 Units 2001 (inhab.) (inhab.) (inhab./km²) San Fernando 144,763 150,467 924 162.8 Tigre1 257,922 300,559 360 834.8 San Isidro 299,023 293,212 48 6108.6 Vicente López 289,505 273,802 39 7,020.5 C. A. De Bs. As. 2,965,403 2,768,772 200 13,843.9 Avellaneda 344,991 329,638 55 5993.4 Quilmes 511,234 518,723 125 4149.7 Berazategui 244,929 287,944 188 1531.6 Ensenada 48,237 51,171 101 506.6 Berisso 74,761 79,862 135 591.5 Magdalena2 22,409 16,495 1.863 8.9 Punta Indio3 ------9,279 1.627 5.7 Chascomús 43,650 45,093 4.225 9.1 Castelli 7,025 7,860 2.100 3.7 Tordillo 1,444 1,743 1.330 1.3 Gral. Lavalle 3,046 3,088 2.649 1.2 La Costa 38,603 59,577 226 263.6 Average Totals 5,296,945 5,197,285 16.195 2,413.9
1. In the case of San Fernando and Tigre counties, the sector of Delta islands has been included. 2. County whose area has been modified; it has transferred land for the creation of Punta Indio County. Provincial Law Nº 11.584/94. 3. Created with lands pertaining to the Magdalena County. Provincial Law Nº 11.584/94.
So far, the INDEC has only provided data from the 2001 CNPyV on total population, population by gender, area of political-administrative units (some of them recently constituted), population density, and population in private homes and in collective institutions. These data are given by county. The complete information of this last census would be available in the course of the year 2003.
TABLE 2 – IDENTIFICATION OF POPULATION FOR THE MABA COASTAL SECTOR, BY CENSUS FRACTIONS AND RADII Political- INDEC Census Census Radius/Radii Population administrative Code Fraction/s (inhabitants)
805 01 All the radii of the 23,121 Tigre fraction are included 02 ----- 25,996 03 ----- 31,249 “ 04 14 1,297 16 1,416 17 1,331 18 1,276 19 1,323 20 1,820 “ 07 10 3,437 11 2,079 14 1,847 15 1,882 “ 08 03 1,080 04 1,452 05 3,412 06 2,432 07 1,932 “ 09 All the radii of the 1,954 fraction are included 10 ----- 2,231 11 ----- 3,199 12 ----- 1,310 13 ----- 10,459 14 ----- 3,807 “ 15 01 2,185 02 2,487 05 1,901 06 1,768 “ 16 01 804 05 2,013 Total for Tigre: 142,500
MAP 3
ANNEX TASK 25B
1. Demographic aspects: 1.1. Total population The “total population” indicator is linked to the characterization of exposure. This indicator gives an idea of the number of people inhabiting the study area, per administrative unit (the counties). By using this indicator, we try to establish the coexistence or spatial coincidence of threat and society.
1.2. Variation in relation to population It is the percentage of increase or decrease of the population registered at the end of the period as compared to the population at the beginning of the period of study. Although the relationship between population growth and increase of vulnerability has not yet been fully assessed, this indicator may be considered to reflect social and economic processes of a wider scope that may be the main causes or dynamic pressures (Blaikie et. al.) in the construction of the conditions of insecurity.
1.3. Population density This indicator is linked to exposure, since it expresses the concentration of persons in a given territory that may be affected by potential risks. As concentration (density) increases, exposure and social vulnerability will increase accordingly. A higher population density, on the other hand, may imply spatial tensions, both in resource use (economic resources, human resources, etc) and in the rendering of services, which may lead to complicated situations when faced with the need to implement actions in an emergency or mitigation situation (movement of evacuated persons and goods, number of centers to be opened and available vehicles).
1.4. Young potential dependency index 1.5. Elderly potential dependency index These two indicators establish a ratio between the economically non-active population and the total potentially active population. The first one reflects the proportion of young up to the age of 15, with respect to the population between 15 and 64 years of age, while the second expresses the proportion of people older than 64 with respect to the age group between 15 and 64 years old. This is a useful differentiation, since the younger and older members of a social group are generally more vulnerable when faced with a given threat (they are less mobile, more dependent, less resistant).
2. Living Conditions 2.1. Percentage of the population in homes with UBN The UBN (unsatisfied basic needs) index is a combination of five indicators that denote situations of want or poverty: three of them represent critical levels of privation as related to the habitat, one is related to a loss of access to education, and the last one is related to the burden that the economically dependent members represent for the home income (thus complementing the information provided by the two potential dependence indices). By detecting all these unsatisfied needs, UBN allows for a better determination of the structural poor, who are generally a more vulnerable group.
2.2. Percentage of homes with female family head In the recent literature on risks and disasters, it is understood that, in general, the gender condition is an attribute that increases social vulnerability. This may happen in societies in which women are denied their basic rights (the right to vote, to inherit land) or in societies in which, for one reason or another, women become family heads. In the latter case, it is understood that a woman in charge of a home (comprising more than one member) plays several simultaneous roles: she supports that home from an economic, affective, and psychological point of view; she looks after and takes care of her children; she performs the domestic chores and obtains an income which, on account of the gender segmentation of the labor market, is lower in average to that of a male family head.
2.3. Total child mortality rate 2.4. Neonatal child mortality rate The mortality rate (the probability that a child may die during his first year of life) and neonatal child mortality (the probability that a child may die during the first 28 days of his life) are indicators that reflect several health situations related with the mother and the child’s health condition during the critical period comprising the first year of life. Given its sensitivity to changes in sanitary conditions, food conditions and other social factors, child mortality rate is considered to be a good general indicator of the health condition of a given population and, at the same time, it reflects situations of greater social vulnerability when faced with threats.
2.5. Percentage of the population with no access to health services The health status of a given social group is related to the degree of susceptibility of that group to be affected by the consequences of a dangerous event. It is generally understood that good health conditions will favor a better preparation, response and recovery, and the group will therefore be less vulnerable.
3. Production and consumption processes 3.1 Rate of unemployment: According to the definition in the 1991 CNPyV 1991 (INDEC), it is the percentage of unemployed population of the total economically active population. Unemployed persons are those who, although they are out of work, are actively looking for a job (open unemployment). This concept does not include other forms of precarious labor, such as people who perform temporary tasks while actively looking for an occupation, those who involuntarily work during less hours than those in a normal working day, unemployed persons who have suspended their search for jobs due to lack of apparent job opportunities, those occupying jobs in positions with remuneration below the minimum vital one or in positions below their qualifications, etc.The unemployed population has less monetary resources to face and recover from a disaster situation.
3.2 Gross Added Value in $ (pesos): According to the 1999 Annual Statistics Report of Buenos Aires Province, it refers to the difference between production value and intermediate consumption. It comprises job remuneration, taxes, depreciation, interests, exchange differences and exploitation surplus (prior to income taxes).
It would be more precise to use the geographic gross product –GGP- (which is defined as the gross value of goods and services, net of the value of elements and goods required in the production process, produced in a period of time by the production factors, within defined boundaries), since this index comprises the gross added value at basic prices plus specific taxes; however, the inconvenience of using the GGP is this indicator has been assessed at the provincial level, and it is not available for smaller political-administrative units (Counties/ Districts).
3.3 Occupied jobs in the manufacturing industry, commerce and services: This indicator assesses occupied jobs, classified in fields of activity (manufacturing industry, commerce, and services). Therefore, we propose the construction of a unique indicator resulting from adding up all occupied jobs in the above-mentioned fields of activity.
3.4 Other indicators currently under assessment Other indicators relative to economic activity and at the same time, indicators of social vulnerability are: Rate of activity, Rate of employment, Total bank deposits of inhabitants of the country in $ and US$, and Total number of registered cars.
Lastly, based on some indicators identified in the above-mentioned sources, another aspect related with resources and expenditure of the political-administrative units (Districts) could be added to the vulnerability index for a given year, taking into account the following: -District Resources (this item includes resources in thousands of pesos available to a given district for a given year) -District personnel for every 1,000 inhabitants (this indicator shows the proportion of district agents for every 1,000 inhabitants. It is assumed that a District with scarce population and a high number of district agents for every 1,000 inhabitants will be reflecting an over-occupation of jobs in the public service, as well as a low diversity of economic activities within the unit) -Amount invested in public works (this indicator shows the amount of resources, in thousands of pesos, invested in public works in general. It may be assumed that part of the sum invested in public works will be used to improve the living conditions of the population –in a wide sense- and/or to mitigate the degree of exposure to dangers through works of engineering (for example: chanels, dams, etc.)
ANNEX TASK 27
Figure 8. Rates of uplift for major structural features along the Argentine coast during the last 10,000 years. 1. C. Espiritu Santo 57° 40´ S 2. B. Langara 48° 30´ S 5. B. Solano 45° 40´ S 7. C. Valdez 42° 30´ S 9. Negro River mouth 41° 10´ S 11. B. Blanca 38° 50´ S 13. Mar Chiquita 37° 30´ S 14 B Samborombón 36° 00´ S 15 Near Paraná Delta 34° 05´ S
NEOTECTONIC FACTOR 2
1.5
1
0.5 Rate ( mm /yr)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Place
ANNEX TASK 28
Buenos Aires 2.50
2.00
1.50
1.00
0.50
0.00 0 86400 172800 259200 345600 432000 518400 604800 691200 777600 864000 -0.50 Medido SHN Predicción SHN
Fig. 1 Recorded and astronomical water levels for January, 1985. Time in seconds, levels in meters
Mar del Plata 2.50
2.00
1.50
1.00
0.50
0.00 0 86400 172800 259200 345600 432000 518400 604800 691200 777600 864000 Medido SHN Predicción SHN
Fig. 2 As in Fig 1
Buenos Aires January 1985 1.50
1.25
1.00
0.75
0.50 Water level (m)
0.25
0.00 96 120 144 168 192 Record Simulation Time (hrs)
Fig, 3 Comparison between recorded and simulated water levels for purely astronomical tide. Time 0 corresponds to hour 0 of January 5 ,1985
Torre Oyarvide January, 1985 1.75
1.50
1.25
1.00
0.75
Water level (m) 0.50
0.25
0.00 96 120 144 168 192
Time (hrs) Record Simulation
Fig, 4 As in Fig 3
Dirección U - Estación: 12.518 2/7/96 al 7/7/96 100
80
60
40
20
0
-20
-40
-60
-80
-100 744 768 792 816 840 864 888
u.12.518 u.sim1.3
Fig, 5 Recorded and simulated eastern water velocity for relatively calm conditions. Station 12 518 is at 35° 16´12´´ S, 56°50´24´´W
Dirección V - Estación: 12.518 2/7/96 al 7/7/96 100
80
60
40
20
0
-20
-40
-60
-80
-100 744 768 792 816 840 864 888
v.12.518 v.sim1.3
Fig, 6 As in Fig 5 , but for northern water velocity
Modelo Hidrodinámico del Río de la Plata Dirección V - Estación: 21.521 - Hora 0 : 00.00hs 20-7-96
100
80
60
40
20
0
-20
-40
-60
-80 120 144 168 192 216 240 264 288 312 336 360 384 408 432 456 480 504 528 552 576 600 v.21.521 v.sim2
Fig 7 Recorded and simulated eastern water velocity
Modelo Hidrodinámico del Río de la Plata Velocidad Total - 21.521 - Hora 0 : 00.00hs 20/7/96 100
90
80
70
60
50
40
30
20
10
0 120 144 168 192 216 240 264 288 312 336 360 384 408 432 456 480 504 528 552 576 600 Vtot.21.521 Vtot.sim2
Fig 8 Recorded and simulated northern water velocity
Fig 9 Wind fields from NCEP and Model ETA
Torre Oyarbide Tormenta 1989 2.0
1.5
1.0
0.5
0.0 nivel (m) -0.5
-1.0
-1.5 72 96 120 144 168 192 tiempo (hr) OBS SIM
Fig. 10 Recorded and simulated water level for the 1989 storm. Time 0 corrresponds to 00 GMT of November 11, 1989
Fig, 11Recorded water level and simulation with HANSOM-CIMA, for the 1989 storm
Palermo Tormenta 1989 4.0
3.0
2.0
1.0
nivel (m) 0.0
-1.0
-2.0 96 120 144 168 tiempo (hr) DIF (shn) dif (hid)
San Clemente Tormenta 1989
4.0
3.0
2.0
1.0
nivel (m) 0.0
-1.0
-2.0 96 120 144 168 tiempo (hr) DIF (shn) dif (hid)
Fig. 12 Recorded and simulated water level for the 1989 storm, with the astronomical tide effects filtered out. Time as in Fig. 10
ANNEX TASK 30
Fig. 1: Wind components along the weather storm of December 6, 1982. In the upper panel according to NCEP/NCAR reanalysis and in the lower panel according to the nested model of high resolution ETA. In red the zonal component of wind and in green the respective meridional component, both at 35º S y 57º W
Fig. 2. Pseudo stress of the wind calculated at the moment of maximum development of the weather storm in May 16, 2000. In the upper panel calculated from NCEP/NCAR reanalysis and in the lower panel from the high resolution nested model ETA.
ANNEX TASK 31
WAVE CONDITION EVALUATION ON THE COAST OF BUENOS AIRES RIO DE LA PLATA – FINAL REPORT
1. INTRODUCTION
The Rio de la Plata (RDP) is a very extensive estuary formed by the confluence of the rivers Paraná and Uruguay. It is located on the east coast of South America, at 35°S (Figure 1).The estuary is about 290 Km long and narrows from 220 Km at its mouth to about 40 Km at its upper end. The RDP can be divided into three regions: upper, with an averaged depth of less than 5m; intermediate, 5-10 m deep and occupied by several shallow sand banks, and an outer region with depths ranging from 10 to 20m. The main characteristics of this estuary are its shallowness and its increasing width (Balay, 1961).
100 R. O. del Uruguay
80 R ío
) d e l m Atalaya a P K l
( a
60 ta
e Buenos Aires c English n Province a
t Bank
s Pta. Piedras i D 40 Argentina Hidrovía's Samborombón Buoy Bay 20
depths in meters Pta. Rasa 0 0 20 40 60 80 100 120 140 Distance (Km) Figure 1 Study Area
Water level fluctuations in the RDP are the sum of three main constituents: tides, storm surges and wind waves. D’Onofrio et al. (1999) estimated the return periods of extreme water levels for some vulnerable low-lying areas of Buenos Aires. Their analysis combines the probability density functions of tides and surges. They obtained for example that the last 89 yr maximum (4.44 m) has a recurrence of approximately 265 yr.
Fiore, et al. (2001) carried out a statistical analysis of surges in Buenos Aires based on hourly residuals for the period 1905-2000. They obtained positive trends for positive and negative surges and explained them as a consequence of a mean sea level rise rather than an increase in the intensity of the storm surges.
Wave conditions over the RDP and their mean characteristics on the coast of Buenos Aires have never been analysed before. The lack of in-situ wave data in the region has only been interrupted in 1996 by the installation of a directional wave recorder Datawell Waverider by Hidrovia S.A. This data set was analysed by Anschutz (2000). In this work it was concluded that the wave climate at the measuring site is a combination of swell and sea fronts, with heights of 0.5 to 1.5 meters and peak periods ranging between 4 and 6 seconds if sea prevails or 10 to 12 seconds if swell prevails. Two-peak spectra were typically present in Anschutz’s analysis. The frequency separating the swell and sea conditions is approximately 1/6 Hz (T= 6 sec.).
The aim of this work was to establish the present mean conditions of sea and swell in the RDP and to attempt an evaluation of possible changes in the wave climate due to future climate variability. Due to the lack of in-situ wave information over the coastal area of Buenos Aires or its proximities, the aforementioned wave records from the outer RDP were used. The study is part of a GEF project on ‘Impact of global change on the coastal areas of the Rio de la Plata: Sea level rise and meteorological effects’.
2. DATA USED
A wave data set a single site within the entire RDP was available from 1996 to 2001. These observations were recorded by Hidrovia S.A. with a directional wave recorder Datawell Waverider. The instrument was moored at approximately 35° 40’ S and 55° 50’ W where the mean depth is 17 m (Figure 1). It was programmed to record every 2 hours 40 minutes. The series consists of 11,297 records gathered from June 1996 to November 2001.
The wave parameters are the characteristic height Hmo (computed as four times the squared root of the
20-minute record total variance) and the peak period. The latter, Tp, corresponds to the peak of the spectrum of instantaneous wave records.
In order to compute the refraction, shoaling and friction along the wave ray, from the buoy to the coast, a bathymetric grid of 1Km spatial resolution was built by digitizing Charts H-113 and H-116 from the SHN (Servicio de Hidrografia Naval).
Directional mean winds used for wave hindcasting have been obtained from the Report of climatological statistics published by the SMN for the period 1981–1990 (Estadisticas Climatologicas 1981–1990, 1992). For the inner and intermediate RDP, Aeroparque J. Newbery’s winds were used. For Punta Piedras, Bahia Samborombón and Punta Rasa, Pontón Prácticos Recalada’s winds were used. Fetch, mean windspeed (Ua), with Ua = 0.71 U 1.23 and frequency (%) for each of the eight directions used, are shown in Table 1. Also given are the names of the five areas selected and the locations from which wind statistics have been extracted from.
N NE E SE S SW W NW
4.5 4.1 4.5 5.5 ------4.8
Inner RDP 45 45 25 175 ------25
Aeroparque 16 12 18 12 ------7 Inter- 4.5 4.1 4.5 5.5 ------4.8 mediate RDP 63 75 200 200 ------113 (Atalaya) 16 12 18 12 ------7
7.8 8.0 8.5 8.9 9.3 -- -- 7.4 Punta Piedras 100 100 200 200 100 -- -- 175
11 16 19 13 10 -- -- 9
7.8 8.0 8.5 8.9 9.3 ------Bahía Sambo- Pontón 188 163 200 200 75 ------rombóm Recalada 11 16 19 13 10 ------
7.8 8.0 ------7.4
175 200 ------75 Punta Rasa 11 16 ------9
Table 1 shows fetch, mean wind speed (Ua) and frequency (%) for each of the eight directions used. Also given are the names of the five areas selected and the locations from which wind statistics have been extracted from.
References Ua - Mean Wind speed (m/s) Fetch (Km) Frequencies (%) 3. MEAN SEA AND SWELL PRESENT CONDITIONS ON THE COAST OF BUENOS AIRES (RDP)
3.1 Wave climate in the outer Rio de la Plata
For the outer region of the RDP, bi-dimensional distributions of heights and periods (Hmo and Tp) for each of the following eight wave directions N, NE, E, SE, S, SW, W and NW were built. Mean as well as maximum conditions were considered. The results are shown in Figures 2 (from a. to h. ).
24 H-T BIDIMENSIONAL DISTRIBUTION 24 22 Datawell Waverider - Hidrovía S.A. H-T BIDIMENSIONAL DISTRIBUTION 22 Wave direction: E Datawell Waverider - Hidrovía S.A. 20 Latitude: 35° 40' S Events: 3161 20 Latitude: 35° 40' S Longitude: 55° 50'W Total events: 11297 Longitude: 55° 50'W 18 Depth: 17 m Depth: 17 m Analysis period: 1996 - 2001 18 Wave direction: SE Events: 4646 16 Total events: 11297 16 Analysis period: 1996 - 2001 ) 14 ds ) 14 n s o d c n e o s 12 c ( e d s 12 ( o
ri d
e o
i
P r 10 e P 10
8 8
6 6
4 4
2 2
0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Height Height (meters) (meters) a) b)
24 2 4 H-T BIDIMENSIONAL DISTRIBUTION H-T BIDIMENSIONAL DISTRIBUTION 22 Datawell Waverider - Hidrovía S.A. 2 2
20 Latitude: 35° 40' S Datawell Waverider - Hidrovía S.A. 20 Longitude: 55° 50'W Latitude: 35° 40' S Depth: 17 m 18 Wave direction: S Longitude: 55° 50'W Wave direction: SW Events: 1607 1 8 Total events: 11297 Depth: 17 m Events: 539 16 Analysis period: 1996 - 2001 1 6 Total events: 11297 Analysis period: 1996 - 2001 ) 14 s ) 14 d s n d o n
c o
e c s 12 e ( (s 12 d o d i r o e eri P 10 P 1 0
8 8 3
6 6
4 4
2 2
0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Height (meters) Height c) d)
Figure 2: H-T bi-dimensional distributions for E, SE, S and SW wave directions. Number of cases are contoured at a 50 contour interval. 24 24 H-T BIDIMENSIONAL DISTRIBUTION H-T BIDIMENSIONAL DISTRIBUTION 22 22 Datawell Waverider - Hidrovía S.A. Datawell Waverider - Hidrovía S.A.
20 Latitude: 35° 40' S 20 Latitude: 35° 40' S Longitude: 55° 50'W Longitude: 55° 50'W Depth: 17 m Depth: 17 m 18 Wave direction: W 18 Wave direction: NW Events: 420 Events: 409 Total events: 11297 Total events: 11297 16 Analysis period: 1996 - 2001 16 Analysis period: 1996 - 2001
) 14 ) 14 s s d d n n o o c c e e
s 12 s 12 ( (
d d o o i i r r e e
P 10 P 10
8 8
6 6
4 4
2 2
0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Height (meters) Height (meters) e) f)
24 24 H-T BIDIMENSIONAL DISTRIBUTION H-T BIDIMENSIONAL DISTRIBUTION 22 22 Datawell Waverider - Hidrovía S.A. Datawell Waverider - Hidrovía S.A.
20 Latitude: 35° 40' S 20 Latitude: 35° 40' S Longitude: 55° 50'W Longitude: 55° 50'W Depth: 17 m Depth: 17 m 18 Wave direction: N 18 Wave direction: NE Events: 278 Events: 237 Total events: 11297 Total events: 11297 16 Analysis period: 1996 - 2001 16 Analysis period: 1996 - 2001
) 14 ) 14 s s d d n n o o c c e e
s 12 s 12 ( (
d d o o i i r r e e
P 10 P 10
8 8
6 6
4 4
2 2
0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Height (meters) Height (meters) g) h)
Figure 2cont: H-T bi-dimensional distributions for E, SE, S and SW wave directions. Number of cases are contoured at a 50 contour interval.
The results indicate that sea and swell conditions were present only in three of the eight wave directions analysed: S, SE, and E, though having different distributions. E waves showed a maximum of 200 sea conditions against 100 cases of swell with periods of approximately 5 sec and 8 sec, and heights of 0.8 to 1.25 m and 0.8 m respectively.
SE waves showed a maximum of 250 swell conditions against 100 cases of sea with periods of approximately 10 sec and heights of 0.8 m for the former, and approximately 5 sec and 1.25 m for the latter. S wave direction showed 25 swell conditions against a maximum of 100 seas, with periods of approximately 11 sec and 4 sec and heights of approximately 0.8 m and 1.25 m respectively.
The bi-dimensional distributions for the other five wave directions NE, N, NW, W and SW showed only sea conditions, all with similar distributions. A mean period of approximately 4 sec was common in all five directions. The most frequent height for NE, N and NW directions was 1 m and 1.5 m for SW and W directions.
The most frequent wave direction for the outer RDP was SE followed by E and S with 4646 (41%), 3161 (28%) and 1607 (14%) cases respectively over a total of 11,297 records. The maximum heights and associated periods for each of the eight analysed directions are given in Table 1. It can be seen that maximum heights corresponded to the E, SE and S waves, which as well were associated with the maximum periods. They were followed by SW wave direction. Lower heights were associated with shorter periods and were present in N, NE, W and NW directions.
General Wave Maximum Height Associated Period True Direction Direction (m) (sec) (degrees) N 2.41 4.8 0 NE 2.22 5.2 34 E 4.55 11.0 101 SE 4.39 8.7 152 S 4.55 8.8 174 SW 3.80 8.3 203 W 2.71 7.0 253 NW 2.51 6.7 321
Table 1 Maximum heights, associated periods and true directions for each of the eight analysed wave directions
Given the geographical position of RDP and its general NNW-SSE orientation, only the waves with E, SE and S directions are able to propagate from the mouth (outer region) to the intermediate and inner regions of the RDP. Swell and sea propagating from the mouth will be highly attenuated by refraction, shoaling and dissipation by bottom friction.
3.2 Mean swell conditions in the Rio de la Plata and, Buenos Aires coast.
Considering those mean wave conditions (characteristic wave height, period and direction obtained from direct observations at the mouth of the river) resulting from Section 3.1 wave propagation and transformation from the outer Rio de la Plata (RDP) towards the coast of Buenos Aires were analyzed by means of a numerical wave transformation computer program. Even though the observations correspond to the location 35° 40’S and 55° 50’W they can be thought as representative of the inner continental shelf adjacent to the RDP. This hypothesis is valid primarily for E, SE, and S ocean wave directions, the only three directions analyzed, given that they are those that will likely enter the estuary.
When a wave train is propagated towards the coast in a zone with irregular bathymetry and under a stationary but spatially variable current field, the wave number must satisfy the modified dispersion relation at any point (Watanabe, 1982). On the other hand, shoaling, refraction and bottom friction effects also transform the amplitude continuously. The refraction coefficient was computed using the classical methodology given by Griswold (1963). Friction and current field effects were also included.
Starting at an initial point in deep waters with wave height, period and direction of incidence obtained from data, the curvature of the ray (computed at this initial point) is used to obtain the change in the direction as the wave progresses a finite distance along the ray. The new refracted direction is obtained and a new position along the ray determined by adding the change to the initial direction. If the curvature at this second estimate of the point does not vary more than 0.001 radian/grid unit from the curvature at the first estimate of the point, the second estimate is accepted as the next point through which the ray passes. If the curvature does vary more than 0.001 radian/grid unit, the iteration continues until the variation is less than 0.001 radian/grid unit. When the criterion is met, the process continues and the obtained (new) point is used as a new starting point. The ray path continues being computed until it has traversed the whole bathymetry and reached the coast. A distance of one-half a grid unit is adopted for computing each point of the ray. A second-order, nonlinear differential equation must be resolved to determine the refraction coefficient at any point along the ray. The refraction coefficient may be smaller (divergence of energy) or greater than one (convergence of energy).
The shoaling coefficient may be based on wave celerity at any point by applying the linear wave- theory. It can be greater or smaller than one, but in shallow waters, near the coast, it is very close to or slightly greater than one. Bottom friction removes energy from waves by interaction of oscillatory wave-induced currents in the seabed, with the sediment and bed forms comprising the seabed. Friction effects always diminish the wave height along the ray. In order to obtain the rate at which energy is removed from waves we have adopted the formulation given by Putnam and Johnson (1942). The friction coefficient adopted in this work was 0.005 suggested by CARP (1992) as the most adequate value for the Rio de la Plata. Energy dissipation was computed along the ray using an integral expression.
Wave heights near the coast of Buenos Aires were computed by multiplying the three coefficients (refraction, shoaling and friction) by the wave heights measured in deep waters in the outer RDP (at the starting point). The results from the transformation computer program are shown in refraction diagrams (Figures 3 a. to d.) For those diagrams waves are assumed to be propagated in the given direction from the outer RDP towards the coast under non-local generated wave conditions. This means that two kinds of mean swell conditions in the RDP are analyzed: short swell, associated to sea in the outer RDP (T<6seg) and long swell, associated to swell in the outer RDP (T>6seg). Diagrams were constructed using initial heights of 1.25m in all cases, but similar conclusions can be obtained using heights having different values within the observed range.
Initial conditions: Initial conditions: 100 R. O. del Uruguay 100 R. O. del Uruguay wave direction: E wave direction: E Tp : 5 sec. Tp : 8 sec. Hmo : 1.25 m Hmo : 1.25 m 80 80 ) ) m m k k ( (
60 60 e e c c Buenos Aires Buenos Aires n n a a t t Province Province s s i i D D 40 40 Argentina Argentina
20 20
depths in meters depths in meters 0 0 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 Distance (km) Distance (km)
a) East Wave Direction – Period 5 sec b) East Wave Direction – Period 8 sec Initial conditions: Initial conditions: 100 R. O. del Uruguay 100 R. O. del Uruguay wave direction: SE wave direction: SE Tp :10 sec. Tp : 5 sec. Hmo : 1.25 m Hmo : 1.25 m 80 80 ) ) m m k k ( (
60 60 e e c c Buenos Aires Buenos Aires n n a a t t Province Province s s i i D D 40 40 Argentina Argentina
20 20
depths in meters depths in meters 0 0 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 Distance (km) Distance (km)
c) South-East Wave Direction – Period 5 sec d) South-East Wave Direction – Period 10 sec.
It can be observed that, in general, waves with short periods (sea, 4 to 5 sec) are the most likely ones to reach the intermediate region of the RDP. The effects of shallow water areas and banks (as the case of the English Bank) have an important role in wave propagation and transformation towards the coast, due to the fact that they yield wave breaking (ray crossing: caustics) producing the consequent wave attenuation. South wave diagrams are not shown given that waves from this direction have no effect on the coast of Buenos Aires, only on the coast of Uruguay.
Shown in Table 2 are the coefficients by which initial heights in the outer RDP were multiplied by in order to compute the wave heights in the proximities of the coast of Buenos Aires. Values are given for each of the analysed directions, characteristic periods and regions within the river. These coefficients were computed by multiplying the refraction, shoaling and friction coefficients (Kr, Ks and Kf, respectively) obtained through the transformation computer program. For example, a wave with a characteristic height of 1.25 m, SE direction, and a period of 5 sec in the outer Rio de la Plata, will become in Samborombón Bay, a wave with a characteristic height of 60% of its initial value. These results are of regional application for the proximities of the coast of Buenos Aires, but not for local use, in which case a specific study shall be done. For example, if the objective were to carry out a particular study of waves in a specific coastal location (close to a pier or to a coastal structure) a higher resolution grid shall be implemented.
Region E SE S
5 sec 8 sec 5 sec 10 sec 4 sec 11 sec
Upper RDP ------
Intermediate 0.1 0.1 0.4 0.6 ------Region of the RDP
0.7 0.4 0.4 0.6 ------Punta Piedras
Samborombón 0.6 0.9 0.6 0.9 ------Bay
Punta Rasa 0.8 0.1 ------(West Side)
Table 2 coefficients by which initial heights in the outer RDP were multiplied by in order to compute the wave heights in the proximities of the coast of Buenos Aires.
The results show that from the outer RDP upstream to Atalaya, waves are formed by a combination of sea and swell (short and long). North of Atalaya, significant swell cannot reach the coast of Buenos Aires hence waves in this region are only locally generated (sea). In the next Section 3.3 the results of the Hindcasting Methodology (SPM) applied to determine the mean sea conditions on the coast of Buenos Aires (RDP) are summarized.
3.3 Mean sea conditions in the RDP, Buenos Aires coast.
The Hindcasting Methodology (Coastal Engineering Manual, 2001) has been applied to five locations from the coast of Buenos Aires, for those wind directions in which wave generation is possible. As W and SW wind directions have no associated fetch, they were not considered in this analysis. Hindcasting has been applied to coastal sites off the surf zone. For SE and NW directions in the inner and intermediate areas of the Rio de la Plata (directions approximately parallel to the coastline), hindcasting points were taken even further offshore. In the central part of the coast of Bahia Samborombón, the N and S directions have no fetch associated, thus hindcasting was carried out at a point off the coast further North for South wind directions and at a point further South for North wind directions. At Punta Rasa, for the particular NE direction, a slightly offshore point was selected in order to avoid the natural sheltering of the geographic accident (cape). In shallow waters, the deep water methodology is applicable under the suggestion from Jensen, 1993 whose recent studies indicate that fetch-limited wave growth in shallow water appears to follow growth laws. These formulas are quite close to deepwater wave growth for the same wind speeds, up to a point where an asymptotic depth-dependent wave height is attained. In light of this evidence, it seems prudent to disregard bottom friction effects on wave growth in shallow water. Also, evidence from Bouws et al. 1985 indicates that wave spectra in shallow water do no appear to have a noticeable dependence on variations in bottom sediments. Consequently, it is recommended that deepwater wave growth formulae be used for all depths, with the constraint that no wave period can row past a limiting value as shown by Vincent (1985) given by: Tp = 9.78 (h / g )½ where h is the mean depth and g is the acceleration due to gravity.
It is desirable to have a simple method for making wave estimates. This is possible only if the geometry of the water body is relatively simple and if the wave conditions are either fetch-limited or duration-limited. Under fetch-limited conditions, winds have blown constantly long enough for wave heights at the end of the fetch to reach equilibrium. Under duration-limited conditions, the wave heights are limited by the length of time the wind has blown. These two conditions represent asymptotic approximations to the general problem of wave growth.
Given the nature of the meteorological data available, the fetch-limited case has been considered herein. In this case, the parameters required are the fetch F and the wind-stress factor Ua (adjusted wind-speed), with Ua = 0.71 U1.23 Where U (in m/s) is the mean wind-speed and represents the average value over the fetch. The spectral wave height Hmo and peak spectral period Tp are the parameters predicted. In this report, these values might be slightly overestimated due to the fact that fetch-limitation has been the single condition applied (duration-limitation condition has not been analyzed). Heights and periods for E and SE wave directions were multiplied by adjusting coefficients (0.4 and 0.7 respectively) in order to fit the hindcasting results with those preliminary results from Mean Swell Conditions in the Rio de la Plata (Section 3.2: Figure 3a, Figure 3c. and Table 2). Likewise, heights and periods from hindcasting for directions N, NE, S and NW for Punta Piedras, Bahia Samborombón y Punta Rasa were multiplied by adjusting coefficients of 0.4 and 0.7 respectively. For the inner and intermediate RDP those coefficients could not be computed, hence Hs and Tp values might be slightly overestimated. Table 3 illustrates the results obtained from hindcasting (i.e. Hmo significant height and Tp peak period). This table also shows the five different locations selected: Inner RDP: Mean heights were around or less than 0.7m and periods did not overcome 4 - 5 sec. Intermediate RDP: Mean heights did not overcome 0.8m and periods resulted similar to those occurred in the inner zone. Therefore, the inner and intermediate RDP can be described as zones with similar sea wave climates. The outer RDP area (Punta Piedras, Bahia Samborombon and Punta Rasa): sea heights were slightly larger than those in the inner and intermediate areas for the E and SE directions. Periods were also longer than those of the abovementioned areas. The highest mean heights observed corresponded to the E and SE directions in the outer RDP.
N NE E SE S SW W NW
0.6 0.6 0.6 0.7 ------0.4 Inner RDP 4 4 4 5 ------4
16 12 18 12 ------7 Aeroparque Inter.- 0.6 0.6 mediate 0.6 0.8 ------0.6 RDP (Atalaya 4 4 4 5 ------4 ) 16 12 18 12 ------7 0.5 0.5 0.9 0.5 0.6 -- -- 0.5 Punta Piedras 4 4 5 5 4 -- -- 4
11 16 19 13 10 -- -- 9
Bahía 0.6 0.6 0.8 0.8 0.5 ------Sambo- Pontón rombóm 5 5 5 5 6 ------Recalada 11 16 19 13 10 ------
0.6 0.6 ------0.4 Punta Rasa 5 5 ------4
11 16 ------9
Table 3 illustrates the results obtained from wave hindcasting for present conditions. Mean significant heights in meters and peak periods in seconds.
References
Heights (m)
Peak Periods (sec)
Frequencies (%)
4. PRESENT MEAN HEIGHT CALCULATION
With the intention of giving an idea of the present mean heights for each of the five RDP areas studied, those values were computed based one the figures in Table 1 by means of the sum:
Total height = H (N) x Freq (N) + H (NE) x Freq (NE) + H (E) x Freq (E) + H (SE) x Freq
(SE) + H (S) x Freq (S) + H (SW) x Freq (SW) + H(W) x Freq (W) + H(NW) x freq (NW) e.g. for the Inner RDP:
Total height = 0.6 x 0.16 + 0.6 x 0.12 + 0.6 x 0.18 + 0.7 x 0.12 + 0.4 x 0.07 = 0.39 m
5. FUTURE MEAN HEIGHT CALCULATION
Considering the hypothesis of an increase in the frequency of winds coming from the East of approximately 30% and considering a decrease in the frequency of winds from the West of the same magnitude, a rough estimation for future mean heights has been carried out for the five locations analysed (Table 4). Below there is an example of how these heights have been computed, for the inner RDP:
Total height = 0.6 x 0.16 + 0.6 x 0.12 + 0.6 x 0.18 x 1.3 + 0.7 x 0.12 + 0.4 x 0.07 = 0.42m
Present Future
Mean Height Mean Height
Inner RDP 0.39 0.42
Intermediate RDP 0.41 0.45
Punta Piedras 0.48 0.53
Bahia Sanborombón 0.47 0.49
Punta Rasa 0.20 0.20
Table 4 shows the results obtained from hindcasting for mean heights for present wave conditions and future wave conditions.
6. DISCUSSION AND SUMMARY OF CONCLUSIONS
For the outer region of the RDP, bi-dimensional distributions of heights and periods for each of the following eight wave directions N, NE, E, SE, S, SW, W and NW were built. The results indicate that sea and swell conditions were present only in three of the eight wave directions analysed: S, SE, and E, though having different distributions. The bi-dimensional distributions for the other five wave directions NE, N, NW, W and SW showed only sea conditions, all with similar distributions.
Given the geographical position of RDP and its general NNW-SSE orientation, only the waves with E, SE and S directions are able to propagate from the mouth (outer region) to the intermediate and inner regions of the RDP. Swell and sea propagating from the mouth will be highly attenuated by refraction, shoaling and dissipation by bottom friction. Considering those mean wave conditions resulting from Section 3.1 (characteristic wave height, period and direction obtained from direct observations at the mouth of the river) wave propagation and transformation from the outer Rio de la Plata (RDP) towards the coast of Buenos Aires were analyzed by means of a numerical wave transformation computer program.
It can be observed that, in general, waves with short periods (sea, 4 to 5 sec.) are the most likely ones to reach the intermediate region of the RDP. The effects of shallow water areas and banks (as the case of the English Bank) have an important role in wave propagation and transformation towards the coast due to the fact that they yield wave breaking (ray crossing: caustics) producing the consequent wave attenuation. South wave diagrams are not shown given that waves from this direction have no effect on the coast of Buenos Aires, only on the coast of Uruguay.
Wave heights in the proximities of the coast of Buenos Aires were obtained by considering the effects of refraction, shoaling and friction over the initial wave conditions in the outer RDP. The results show that from the outer RDP upstream to Atalaya, waves are formed by a combination of sea and swell (short and long). North of Atalaya, significant swell cannot reach the coast of Buenos Aires hence waves in this region are locally generated (sea) exclusively. The Hindcasting Methodology (Coastal Engineering Manual, 2001) has been applied to five locations from the coast of Buenos Aires, for those wind directions in which wave generation is possible. The results obtained from hindcasting are: Inner RDP: Mean heights were around or less than 0.7m and periods did not overcome 4 - 5 sec. Intermediate RDP: Mean heights did not overcome 0.8m and periods resulted similar to those occurred in the inner zone. Therefore, the inner and intermediate RDP can be described as zones with similar sea wave climates. Outer RDP (Punta Piedras, Bahia Samborombon and Punta Rasa): sea heights were slightly larger than those in the inner and intermediate areas for the E and SE directions. Periods were also longer than those of the abovementioned areas. The highest mean heights observed corresponded to the E and SE directions in the outer RDP.
Finally, considering the hypothesis of an increase in the frequency of winds coming from the East of approximately 30% and considering a decrease in the frequency of winds from the West of the same magnitude, a rough estimation for future mean heights has been carried out for the five locations analysed.
REFERENCES
Anschütz, Gustavo (2000) Comparison between SAR-ERS and Waverider Buoy Meaurements in the Outer Rio de la Plata.
Balay M. A. (1961) El Rio de la Plata entre la atmósfera y el mar. H-621 Servicio de Hidrografía Naval. Armada Argentina, 166 pp.
Shore Protection Manual (1984) U:S: Army Coastal Engineering Research Center
Coastal Engineering Manual (2002), U:S: Army Coastal Engineering Research Center
Fiore M.E., D'Onofrio E.E., Di Biase F., Stadelmann M., Statistical Analysis of storm surges in Buenos Aires. Fue presentado durante las jornadas “2001 Joint Assemblies of the International Association for the Physical Sciences of the Oceans and International Association for Biological Oceanography”, realizadas en Mar del Plata en Octubre de 2001.
D'Onofrio, E.E., Fiore, M.E., Romero, S.I. (1999), Return periods of extreme water levels estimated for some vulnerable areas of Buenos Aires. Continental Shelf Research, 19, 1681- 1693.