The Historic Flood Map is a GIS layer showing the maximum extent of individual Recorded Flood Outlines from river, the sea and groundwater springs that meet a set criteria. It shows areas of land that have previously been subject to flooding in England. This excludes flooding from surface water, except in areas where it is impossible to determine whether the source is fluvial or surface water but the dominant source is fluvial.

The majority of records began in 1946 when predecessor bodies to the Environment Agency started collecting detailed information about flooding incidents, although we hold limited details about flooding incidents prior to this date.

If an area is not covered by the Historic Flood Map it does not mean that the area has never flooded, only that we do not currently have records of flooding in this area that meet the criteria for inclusion. It is also possible that the pattern of flooding in this area has changed and that this area would now flood or not flood under different circumstances. Outlines that don’t meet this criteria are stored in the Recorded Flood Outlines dataset.

The Historic Flood Map takes into account the presence of defences, structures, and other infrastructure where they existed at the time of flooding. It will include flood extents that may have been affected by overtopping, breaches or blockages.

Flooding is shown to the land and does not necessarily indicate that properties were flooded internally.

Groundwater is the water that soaks into the ground from rain and can be stored beneath the ground. Groundwater floods occur when the water stored beneath the ground rises above the land surface. The Historic Groundwater Flood Mapshows the observed peak flood extents caused by groundwater in Ireland. This map was made using satellite images (Copernicus Programme Sentinel-1), field data, aerial photos, as well as flood records from the past. Most of the data was collected during the flood events of winter 2015 / 2016, as in most areas this data showed the largest floods on record.The map is a vector dataset. Vector data portray the world using points, lines, and polygons (area). The floods are shown as polygons. Each polygon has info about the type of flood, the data source, and the area of the flood.The flood extents were calculated using data and techniques with various precision levels, and as such, it may not show the true historic peak flood extents.The Winter 2015/2016 Surface Water Flooding map shows fluvial (rivers) and pluvial (rain) floods, excluding urban areas, during the winter 2015/2016 flood event, and was developed as a by-product of the historic groundwater flood map.The map is a vector dataset. The floods are shown as polygons. Each polygon has info about the type of flood, the data source, and the area of the flood.The flood extents were made using remote sensing images (Copernicus Programme Sentinel-1), which covered any site in Ireland every 4-6 days. As such, it may not show the true peak flood extents.

Collection of flood and inundation maps over Queensland at various scales 1893-1974, these show flood levels and probable inundation areas at various flood heights. A number of the map series include key maps.

Note: Each CSV in this series includes basic metadata about each map in the series and a URL to access a high resolution scan of each map.

Flood extents and maximum flood maps for flood events of May 2003, Dec 2007, Nov-Dec 2008, May 2010, and Dec 2014, based on a time series of EO SAR data and optical data. The satellite imagery used, and validation and accuracy measures vary by flood event. Please consult the resources for details from respective flood events. This dataset is one of the products produced under the 2014-2016 World Bank (WBG) European Space Agency (ESA) partnership, and is published in the partnership report: Earth Observation for Sustainable Development, June 2016.

Flood maps calculated from space-borne remote sensing Synthetic Aperture Radar (SAR) VV backscatter data during the extreme hydro-meteorological events occurred along the Panaro River . Sentinel 1/TerraSarX SAR data has been processed by a method combining thresholding and segmentation (CThS method). The main idea of CThS is to find some samples which are definitely seeds of the flood water areas. In doing so, a statistical measure of randomness, i.e. entropy filtering, is applied to characterize the texture of the input image. It tries to find locally some pixels, which contain the entropy values of the 3-by-3 neighborhood around the corresponding pixel in the input image. What the local filtering identifies is areas with a significant difference with the surrounding areas. These areas could contain different ground targets, which have the same signature as water. Then histogram thresholding is performed. The histogram of all pixels extracted by filtering is reasonably bimodal so that a suitable threshold value can be determined by fitting a curve to the histogram to separate water and non-water pixels. Having separated water seed points, an active contour segmentation method is used to delineate the full flood extent. The dataset contains flood maps for the dates: 12 and 13 December 2017 and water maps on 20 January 2014 and 8 December 2020. You are not authorized to view this dataset. You may email the responsible party OPERANDUM to request access. Flood maps of historical flood events (Panaro)

Recorded Flood Outlines is a GIS layer which shows all our records of historic flooding from rivers, the sea, groundwater and surface water. Each individual Recorded Flood Outline contains a consistent list of information about the recorded flood.

Records began in 1946 when predecessor bodies to the Environment Agency started collecting detailed information about flooding incidents, although we may hold limited details about flooding incidents prior to this date.

The absence of coverage by Recorded Flood Outlines for an area does not mean that the area has never flooded, only that we do not currently have records of flooding in this area.

It is also possible that the pattern of flooding in this area has changed and that this area would now flood or not flood under different circumstances.

The Recorded Flood Outlines take into account the presence of defences, structures, and other infrastructure where they existed at the time of flooding. It includes flood extents that may have been affected by overtopping, breaches or blockages.

Any flood extents shown do not necessarily indicate that properties were flooded internally.

A companion dataset Historic Flood Map contains a subset of these Recorded Flood Outlines which satisfy a certain criteria.

This is a proof of concept web service displaying trial samples of historic flood mapping from satellite. Over the next 2 years this service will be developed into a nationwide portal displaying flooding across Australia as observed by satellite since 1987.The service shows a summary of water observed by the Landsat-5 and MODIS satellites across Australia for periods between 2000 and 2012.The first layer set displays national observed water from MODIS fvrom 2000 to 2012, as derived by Geoscience Australia using an automated flood mapping algorithm. The colouring of the display represents the frequency of observed water in a 500 x 500m grid. The higher the number, the more often water was observed by the satellites over the period. This means that floods have low values, while lakes, dams and other permanent water bodies have high values.The three additional layer sets are study areas demonstrating the water observed in each study area by the Landsat-5 satellite, as derived by Geoscience Australia using an automated flood mapping algorithm. The study areas and the observation periods are:Study Area 1, Condamine River system between Condamine and Chinchilla, Qld, observed between 2006 and 2011Study Area 2, North-west Victorian rivers between Shepparton and Kerang, observed between 2006 and 2011Study Area 3, Northern Qld rivers, near Normanton, observed between 2003 and 2011Each Study Area layer set includes a water summary displaying the frequency of observed water in 25 x 25m grids, plus individual flood extents for specific dates where flooding was observed. Similar to the national, MODIS summary, the higher the value, the more often water was observed by the satellites over the period. Limitations of the InformationThe automated flood mapping algorithm can confuse cloud shadows and snow with flood water, so some areas shown as water may be incorrect. This is a proof of concept dataset and has not been validated.

Flood risk areas display the extent of known historical flood events as well as areas that have a probability of flooding as determined from historical records. The polygon data includes the description of the flood event, the typical causes of the flood and any associated place name keys. The line data indicates the limits of the flood risk mapping information and the 2008 and 2018 flood data. Flood extents for the 2008 and 2018 Lower Saint John River floods are included.

FloodScan uses satellite data to map and monitor floods daily, helping compare current flood conditions with historical averages. This dataset contains two resources:

The first (hdx_floodscan_zonal_stats.xlsx) is a daily tabular dataset providing average FloodScan Standard Flood Extent Depiction (SFED) flood fraction (0-100%) per admin 1 and 2 level. Historical baseline values (SFED_BASELINE) are calculated per day-of-year from the last 10 years of historical data (non-inclusive of current year) after applying an 11 day smoothing mean window. Return Period (RP) is calculated empirically based on all historical data up to the current year (non-inclusive).

The second resource (aer_floodscan_300s_SFED_90d.zip) is a zipped file containing AER FloodScan estimated daily flood fraction (0-100%) gridded data at approximately 10 km resolution (300 arcseconds equivalent to approximately 0.083 degrees) for the last 90 days. Each file represents the estimates for a single day and includes 2 bands: SFED and SFED_BASELINE. The baseline band provides users an easy way to compare current values with historical averages. The baseline is calculated per day-of-year from the last 10 years of historical data (non-inclusive of current year) after applying an 11 day temporal smoothing mean window.

Introduction

The Historical Flood Events map service is a multi layered dataset which shows known areas that have been inundated by flood water in the past. These flooded area outlines have been generated from archived field data and aerial photographs that were collected by Rivers Agency at the time of the actual flood events. In all, over 60 separate events are recorded going back to 1971. The following layers are included: • Historical Flood Outlines • Locations of Aerial Photographs indicating flooding

Purpose of the data

The data is used to understand where flooding has occurred in the past and to provide records of the details. Absence of an historic flood event outline for an area does not mean that the area has never flooded, only that the Rivers Agency does not currently have records of flooding in this area. Similarly, the inclusion of a record of a flood event outline does not necessarily mean that the area will flood again. Flood alleviation schemes will have been undertaken at some of the flood prone locations and this work will have significantly reduced the likelihood of future flooding at these areas

Data Coverage

All of Northern Ireland, and some limited coverage in Republic of Ireland in border areas. Data Format OGC (Open Geospatial Consortium) compliant Web Mapping Service in WGS 1984 projection, accessible via secure website (requires authentication by user specific username and password)..

Data content

Historical Flood Outline • the spatial outline • flood event code • the outline code • names of the event outline • start and end dates • flood extent source • source and cause of flooding • flags indicating if the flood was River, coastal, surface water, out of sewer Aerial Photographs • the spatial outline • Comments • Direction • Event Date • Photo Reason • River Name

Abstract

This dataset and its metadata statement were supplied to the Bioregional Assessment Programme by a third party and are presented here as originally supplied.

Polygon data delineating modelled statistical flood extent with an Average Recurrence Interval (ARI) of 100 years. For historical/actual flood extents, refer to 'Historic_extent' layer. Also known as the 1 in 100 year flood layer, it is used, among other things, in the creation of 'Land Subject to Inundation' areas as used in Planning Scheme Zones. The 1 in 100 year data is not restricted. This data is part of a group of layers depicting a range of statistical ARI extents. Current layers include 5, 10, 20, 30, 50, 100, 200, 500, 1000 year intervals, each in a separate dataset. The layer called EXTENT_PMF represents areas of 'probable maximum flood' and is also part of this group. The data is statistically derived using hydrological models, historic flood extents and heights.

Purpose

Mainly used for municipal planning and risk assessment. The EXTENT_100Y_ARI layer is deemed the most appropriate to use for determining areas at risk of flooding. This layer directly inputs into the Land Subject to Inundation overlay. (LSIO)

Dataset History

Lineage: Primary

Positional Accuracy: Precision: 5m to 100m Initial data, flagged as 'modified = 20000101' varies in accuracy, and should be treated with caution, particularly at scales less than 1:25,000. Data with 'modified' values later than 20000101 are quite accurate and mostly sourced from flood studies. This data is suitable to use at township and parcel level. Reliability field provides clues to the accuracy, where a value of 1 is best and 3 is worst.

Attribute Accuracy: Attributes are verified and should be accurate. Overall reliability of the source material is indicated in RELIABILITY field, where 'HIGH' is good and 'LOW' is poor quality source information.

Logical Consistency: Attributes are consistent with other related layers e.g. flood height contours

Data Source: Flood data dates back to mid 1800s and historically has been predominantly located in DNRE Floodplain Management. Some data is located in Water Authorities.

Completeness: Floodplain Management Unit mapping conventions on definitions of flood mapping height data will be followed.

Additional Metadata: Recommend liaison with Floodplain Management Unit to clarify use of this layer

Refer to mapping reports for each major data capture effort to be kept at DNRE Floodplain Management Unit.

Dataset Citation

Victorian Department of Environment and Primary Industries (2014) Victoria - 1 in 100 Year Flood Extent. Bioregional Assessment Source Dataset. Viewed 05 October 2018, http://data.bioregionalassessments.gov.au/dataset/6e59ed35-3fde-48e3-8135-eb05263ce4aa.

Heavy rainfall occurred across Louisiana during March 8-19, 2016, as a result of a massive, slow-moving southward dip in the jet stream, which moved eastward across Mexico, then neared the Gulf Coast, funneling deep tropical moisture into parts of the Gulf States and the Mississippi River Valley. The storm caused major flooding in north-central and southeastern Louisiana. Digital flood-inundation maps for a 4.3-mile reach within the community of Monroe near Black Bayou in Ouachita Parish, LA was created by the U.S. Geological Survey (USGS) in cooperation with Federal Emergency Management Agency (FEMA) to support response and recovery operations following a March 8-19, 2016 flood event. The inundation maps depict estimates of the areal extent and depth of flooding corresponding to 4 high-water marks (HWM) identified and surveyed by the USGS following the flood event.

Recorded Flood Extents shows areas that have been recorded to have flooded in the past from rivers, the sea or surface water. The records come from a number of evidence sources including Natural Resources Wales, its predecessors or other Risk Management Authorities.

It is possible that the pattern of flooding in an area may have changed and would now flood under different circumstances. In addition, the absence of a recorded flood extent does not mean that the area has never flooded, only that we do not currently have records of flooding in this area.

The Flood Mapping Team within NRCan’s Canada Centre for Mapping and Earth Observation (CCMEO) has completed the digitization of these approximately 1400 historical flood events. By scraping publication records for flood event details, they created a publicly available data layer consisting of point data with attributes for flood location, years/seasons, and details. Sources are available for every point. The maps can be a starting point for understanding regional flood trends or for training machine learning models for predicting nation-wide flood risk.CCMEO’s Flood Mapping Team is advancing flood mapping practices in Canada by leading the Flood Hazard Identification and Mapping Program, compiling existing flood hazard data through the National Flood Hazard Data Layer, digitizing historical flood maps, publishing flood mapping guidelines, and researching innovative ways to advance flood mapping practices relating to geomatics. Overall, the modernization of flood mapping practices will help communities understand and manage their flood risk.The point groupings correspond to the locations that were affected by the same event. The inventory of past flooding has been compiled from various public sources and standardized into a common data model. Flooding events for which no location was included in the sources are positioned on the place name of the location affected by the flooding. The event positions do not indicate where the flooding occurred. It should be noted that no consultation was conducted with the various providers and stakeholders of historical flood data. Disparities in content between the various sources result in an inconsistent product. No warranty is given as to the accuracy or completeness of the information provided. The absence of information does not mean that no flooding has occurred.Additional Resources:Historical flood events (HFE) data page on open.canada.caArticle on the historical flood events layerFlood Hazard Identification and Mapping ProgramUpdate Frequency: Ongoing

The Flood Map for Planning (Rivers and Sea) includes several layers of information. This dataset covers Flood Zone 2 and should not be used without Flood Zone 3. It is our best estimate of the areas of land at risk of flooding, when the presence of flood defences are ignored and covers land between Zone 3 and the extent of the flooding from rivers or the sea with a 1 in 1000 (0.1%) chance of flooding each year. This dataset also includes those areas defined in Flood Zone 3.This dataset is designed to support flood risk assessments in line with Planning Practice Guidance ; and raise awareness of the likelihood of flooding to encourage people living and working in areas prone to flooding to find out more and take appropriate action.The information provided is largely based on modelled data and is therefore indicative rather than specific. Locations may also be at risk from other sources of flooding, such as high groundwater levels, overland run off from heavy rain, or failure of infrastructure such as sewers and storm drains.The information indicates the flood risk to areas of land and is not sufficiently detailed to show whether an individual property is at risk of flooding, therefore properties may not always face the same chance of flooding as the areas that surround them. This is because we do not hold details about properties and their floor levels. Information on flood depth, speed or volume of flow is not included.NOTE: We have paused quarterly updates of this dataset. Please visit the “Pause to Updates of Flood Risk Maps” announcement on our support pages for further information. We will provide notifications on the Flood Map for Planning website to indicate where we have new flood risk information. Other data related to the Flood Map for Planning will continue to be updated, including data relating to flood history, flood defences, and water storage areas.Defra Network WMS server provided by the Environment Agency

FloodScan uses satellite data to map and monitor floods daily, helping compare current flood conditions with historical averages. This dataset contains two resources: The first (hdx_floodscan_zonal_stats.xlsx) is a daily tabular dataset providing average FloodScan Standard Flood Extent Depiction (SFED) flood fraction (0-100%) per admin 1 and 2 level. Historical baseline values (SFED_BASELINE) are calculated per day-of-year from the last 10 years of historical data (non-inclusive of current year) after applying an 11 day smoothing mean window. Return Period (RP) is calculated empirically based on all historical data up to the current year (non-inclusive). The second resource (aer_floodscan_300s_SFED_90d.zip) is a zipped file containing AER FloodScan estimated daily flood fraction (0-100%) gridded data at approximately 10 km resolution (300 arcseconds equivalent to approximately 0.083 degrees) for the last 90 days. Each file represents the estimates for a single day and includes 2 bands: SFED and SFED_BASELINE. The baseline band provides users an easy way to compare current values with historical averages. The baseline is calculated per day-of-year from the last 10 years of historical data (non-inclusive of current year) after applying an 11 day temporal smoothing mean window.

The Global Flood Database contains maps of the extent and temporal distribution of 913 flood events occurring between 2000-2018. For more information, see the associated journal article. Flood events were collected from the Dartmouth Flood Observatory and used to collect MODIS imagery. The selected 913 events are those that were successfully mapped (passed quality control as having significant inundation beyond permanent water) using 12,719 scenes from Terra and Aqua MODIS sensors. Each pixel was classified as water or non-water at 250-meter resolution during the full date range of each flood event and subsequent data products were generated including maximum flood extent ("flooded" band) and the duration of inundation in days ("duration" band). Water and non-water classifications during a flood event include permanent water (here resampling the 30-meter JRC Global Surface Water dataset representing permanent water to 250-meter resolution), which can be masked out to isolate flood water using the "jrc_perm_water" band. Extra data quality bands were added representing cloud conditions during the flood event (e.g., "clear_views" representing the number of clear days the flood was observed between its start and end dates and "clear_perc" representing the percentage of clear day observation of the total event duration in days). Each image in the ImageCollection represents the map of an individual flood. The collection can be filtered by date, country, or Dartmouth Flood Observatory original ID.

This shapefile (polygon feature) contains the boundary of the July 1, 2022 100-Year Storm Flood Risk Zone, one of the layers of the July 1, 2022 100-Year Storm Flood Risk Map. Areas within this boundary are highly likely to experience “deep and contiguous” flooding during a 100-year storm. A 100-year storm is a storm that has a 1% chance of occurring in a given year. “Deep and contiguous flooding” means flooding at least 6-inches deep spanning an area at least the size of an average City block. The 100-Year Storm Flood Risk Zone does not provide the exact depth of flooding at a given location. It also does not show areas in the City that may experience shallower and/or more localized flooding in a 100-year storm. Finally, the 100-Year Storm Flood Risk Zone shows flood risk from storm runoff only. It does not consider flood risk in San Francisco from other causes such as shoreline overtopping and overland inundation from the San Francisco Bay or Pacific Ocean. In addition to the 100-Year Storm Flood Risk Zone, the 100-Year Storm Flood Risk Map shows: • “Areas not served by the Combined Sewer and Stormwater Collection System” - showing where data for rainfall driven storm runoff is not available, and where flood risk has not been analyzed. • “Historical Shoreline”, “Historical Creeks”, and “Historical Waterbodies” - historical hydrology layers to illustrate the general topography of low-lying areas in the City. The Horizontal Datum used for the GIS layers is “NAD_1983_2011_StatePlane_California_III_FIPS_0403_Ft_US.” Notes on Usage At a minimum, the 100-Year Storm Flood Risk Map is updated by the San Francisco Public Utilities Commission (SFPUC) on an annual basis on or before July 1 to account for any parcel review requests that remove properties from the Flood Zone. To confirm the latest version of the 100-Year Storm Flood Risk Map, check the SFPUC website at https://sfpuc.org/learning/emergency-preparedness/flood-maps to see if the map has been updated since the date of this shapefile or if there have been any parcel review determinations that identify parcels that are no longer part of the 100-Year Flood Risk Zone. The most recent official map, associated documentation, and list of parcels removed from the map from a parcel review process are available at https://sfpuc.org/learning/emergency-preparedness/flood-maps. Please be advised that the parcels listed are no longer considered to be within the 100-Year Flood Risk Zone as a result of the parcel review process. As of July 2022, this list is updated on an ongoing basis. Check the SFPUC website for any changes to this schedule. The boundaries of this zone align with San Francisco parcel boundaries. The user should confirm proper projection or use of the webmap at https://sfpuc.org/learning/emergency-preparedness/flood-maps to properly identify parcels within the flood zone.

North Carolina Effective Flood zones: In 2000, the Federal Emergency Management Agency (FEMA) designated North Carolina a Cooperating Technical Partner State, formalizing an agreement between FEMA and the State to modernize flood maps. This partnership resulted in creation of the North Carolina Floodplain Mapping Program (NCFMP). As a CTS, the State assumed primary ownership and responsibility of the Flood Insurance Rate Maps (FIRMs) for all North Carolina communities as part of the National Flood Insurance Program (NFIP). This project includes conducting flood hazard analyses and producing updated, Digital Flood Insurance Rate Maps (DFIRMs). Floodplain management is a process that aims to achieve reduced losses due to flooding. It takes on many forms, but is realized through a series of federal, state, and local programs and regulations, in concert with industry practice, to identify flood risk, implement methods to protect man-made development from flooding, and protect the natural and beneficial functions of floodplains. FIRMs are the primary tool for state and local governments to mitigate areas of flooding. Individual county databases can be downloaded from https://fris.nc.gov Updated Jan 17th, 2025.

The PHE benchmarks are an important element in the flood risk prevention and information system, as they make it possible to provide a concrete visual and precise element of the threat of major flooding that weighs on a large number of rivers in France. Watch out! The reported historical flood levels are by no means a guarantee that the water level will not rise above. It only testifies to the reality of a prevailing and cyclical risk in the area. To learn more about high water markers and high flood markers, you can visit the major hazards site: Prim.net: link in “Internet Address (URL)”.