DFO Flood Event 4475

Uruguay, May 27- June 12, 2017

Flood Map

Layers, bottom to top (no transparent layers): Red is flooding mapped from ESA Sentinel 1 SAR data. Blue is a reference normal water extent. Light gray is all previously-mapped flooding. Urban areas (satellite-visible lights) are shown in dark gray.

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Event Reporting:

The Flood Observatory maintains a Global Active Archive of large flood events, 1985 to present. This listing is available to the public in both spreadsheet and GIS formats (both formats together provide the complete Archive). New events are entered into this archive each week. As of the end of 2016, there were 4432 events; each has a unique archive number. A single GIS polygon for each event defines in approximate terms the total area affected.

Event Mapping:

In some cases, severe or damaging floods become the focus of Observatory inundation mapping. As part of collaborations with other organizations, and the Global Flood Partnership, the Observatory's maps and other data are made available to the public. With attribution, they can be used freely, including for commercial purposes, under the terms of the Creative Commons license shown below. Geotif versions and GIS files are also provided for these maps through the links below.

This event is selected for Observatory production of map and GIS data products.This web page and associated image and map (GIS) files are the permanent Flood Observatory record of this event. As the flood event proceeds, additional flood extent layers are added; the objective is mapping of the maximum extent flooded.

This Event:

Provided here is brief information leading to the selection of this flood for mapping.

Media/Agency reports: According to FloodList: "Uruguay – Flooding Uruguay River Displaces 1,700 2 JUNE, 2017 BY RICHARD DAVIES IN AMERICAS, NEWS. Increasing levels of the Uruguay River and its tributaries have forced around thousands to evacuate their homes in Uruguay, Argentina and Brazil. Uruguay Uruguay's National Emergency System (SINAE) reports that flooding of the Uruguay River has displaced 1,754 in the departments of Salto, Paysandú and Artigas. Some of the evacuees have been in temporary accommodation for over 1 week. Some areas have been affected by flooding since 24 May after a storm brought heavy rain to river catchments. On May 26 evacuations were carried out in Artigas, Cerro Largo and Salto and in Paysandú two days later. By 30 May around 500 people had evacuated their homes. The number of those displaced has risen over the last 3 days after further rainfall in the Uruguay River basin. From the total number displaced, 573 were evacuated by the authorities to temporary shelters and 1,098 were self-evacuated and are staying in private homes or self-managed camps. SINAE says that those displaced are receiving comprehensive care, including shelter, food and medical supplies. The worst hit department is Salto, where almost 1,300 have been displaced. In Paysandú, 408 people have been displaced and 47 in Artigas. The department of Cerro Largo has also been affected by floods. However, 45 people who were evacuated earlier in Rio Branco in Cerro Largo have since been able to return to their homes. More heavy rain is expected early next week. With river levels already high and soil saturated, SINAE says that further evacuations are likely. Brazil and Argentina Parts of the neighbouring state of Rio Grande do Sul in Brazil have also been affected by flooding. As of 31 May over 2,500 people had been displaced. On 27 May evacuations were carried out in parts of Argentina as a result of flooding from the Uruguay River. According to the Telam news agency, 32 families were evacuated in Concordia and a further 17 families in Concepción del Uruguay."

In addition to the maps above, for web map service-based (WMS) information visit this DFO link. Zoom in to location of interest, and turn on appropriate event and other data layers. See this link for examples of WMS output for this flood.

Flood Magnitude: Moderate

The Flood Observatory uses three criteria to produce a summary flood magnitude estimate. This estimate is provided as moderate, major, very severe, and extreme.

How the estimate is produced: 1) Where at least one River Watch site is monitoring the flood, flood magnitude can be evaluated using a recurrence interval approach. In recurrence interval years, 1.5-5 is moderate, 5-10 is major, 10-25 is very severe, and > 25 is extreme. 2) A separate flood magnitude value is also calculated for each River Watch site. The flood hydrograph water volume is evaluated against the flood of record (which has a magnitude = 10). Four intervals also define this assessment: 1-3, 3-5, 5-7, and 7-10. 3) The flood inundation extent is visually evaluated in the flood map by comparison to maximum extent of flooding ever mapped. Three intervals are useful: moderate (significant flooding), major, and extreme (flood extent at many locations as large or larger than any previously mapped).

Related Data:

River Watch satellite gauging sites provide passive microwave radiometry-based measurements of daily river discharge. Click on the colored map dots to retrieve the discharge record. The discharge time series below is an example from Site 792.

International Charter/Copernicus/UNOSAT Responses:

The International Charter for Space and Major Disasters was invoked on June 6, 2017 (Activation Page). The requesting agency was: Sistema Nacional de Emergencias - Presidencia de la República. The Project Manager was: CONAE (Comisión Nacional de Actividades Espaciales), which is the Argentine Space Agency. The Charter's description of the event as of June 6 was: "Heavy rains caused severe flooding in Uruguays' Salto Department, Paysandú Department and Bella Unión city of the Artigas department displacing 3500 people. Uruguay's National Emergency System (SINAE) are visiting affected areas to assess the damage and prepare relief efforts. Many of the displaced people are already receiving food, shelter and medical care. Northern parts of Uruguay have been under a heavy rain warning since 24 May, and authorities expect further rain with flood waters set to continue rising." CONAE produced flood inundation maps using SPOT 6, SPOT 7, CARTOSAT-2, ALOS-2, RADARSAT-2, and TanDEM-X data and published these as large format .jpg file (see link to activation page above).

Copernicus was not activated. UNOSAT was not activated.

Image Data Sources:

NASA Landsat 8 and ESA Sentinel SAR data if used in this map were obtained from the the U.S. Geological Survey Hazards Data Distribution System. and the Sentinels Science Data hub, respectively. Landsat 8 is jointly managed by NASA and the United States Geological Survey.

Notes on Sentinel SAR data processing: Most commonly, two "exact repeat" images are retrieved from ESA's Sentinels Data hub, from before the flood and during the flood. ESA SNAP software is used to reproject the two images into a geographic (latitude and longitude) coordinate system. A 5x5 low pass filter is applied to both images. A threshold ranging from 50-60 is applied to the flood image, resulting in a subset of only very dark (interpreted as water) pixels. A threshold of .5-.7 is applied to a flood image/preflood image ratio product, resulting in a subset of pixels much darker in the flood image then before (this removes permanent surface water). A Boolean "AND" step then provides only pixels that satisfy both conditions.The exact thresholds used vary in the ranges provided; more strict thresholds map less flood water but also produce less false-positive errors. GIS vectors (polygons) are fit around pixels in the final "flood water" result: the red areas on the flood event maps, and the provided shp files.

GIS Data For These Maps:

Flood extent files (Shp or Mapinfo) supporting this Flood Event Map are located here.

These files may include high spatial resolution mapping such as from Sentinel or Landsat, or lower resolution files from MODIS. File names commonly include the sensor source (e.g., S1 for Sentinel 1, LS8 for Landsat, MODIS for MODIS).

Click here for access to an automated daily MODIS-derived .shp file GIS record (record commences in 2011). Choose appropriate 10 deg x 10 deg map sheet directory and appropriate dates; longitude and latitudes refer to upper left map sheet corner. Not all floods are mappable at the MODIS spatial resolution of 250 m, Some DFO event maps also include these automated MODIS data.

Data from the Global Surface Water Explorer is included as part of the light gray previous satellite-mapped water extent. It is based on Landsat data at a spatial resolution of 30 m (Jean-Francois Pekel, Andrew Cottam, Noel Gorelick, Alan S. Belward, High-resolution mapping of global surface water and its long-term changes. Nature 540, 418-422, 2016). The NASA Shuttle Water Boundary Data (SWBD) surface water extent (90 m resolution), blue, was derived from NASA's the 11-day February, 2000, SRTM mission and this "permanent" water layer was also corrected using Landsat data.

When used, NASA NRT Global Flood Mapping maximum water extent for the years 2013-2015, at 250 m spatial resolution, provide part of the (light gray) previous satellite-mapped water extent layer. DFO creates these annual water extent layers from data provided by that project, by accumulating into one annual file all of the daily .shp files for each year. DFO has also produced flood extent files through mapping of individual floods (~ yr 2000 to present); these are also included in this layer.

Point of Contact:

The Flood Observatory needs your input. If the information provided here is of value, please send a brief email to: Robert.Brakenridge @ Colorado.edu. No email addresses are shared. It is essential for the sustainability of our work that you do this.

Funding, Data, and Institutional Support:

The NASA Earth Sciences Program, the Latin American Development Bank, the World Bank, the European Commission (Global Disaster Alert and Coordination System, GDACS), the Google Earth Engine research awards program, the Committee on Earth Observation Satellites (CEOS) Disasters Working Group-Flood Pilot, the Japanese Space Agency, and the European Space Agency all have supported this work via research grants and contracts or by provision of free satellite-derived data.

The Dartmouth Flood Observatory was founded in 1993 at Dartmouth College, Hanover, NH USA and moved to the University of Colorado, INSTAAR, CSDMS in 2010. The institutional support of both universities is gratefully acknowledged.

Creative Commons License
This work, web site, and associated data are by G. R. Brakenridge and A. J. Kettner and are provided for use under the terms of a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.



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