This record is for Approval for Access product AfA435. Listing of Severe Flood Warnings, Flood Warnings and Flood Alerts issued since the flood warning system went live on January 26th 2006 to the present. This dataset includes flood warnings issued by the Environment Agency. Flood warnings are issued for flooding from rivers and the sea and, for a limited number of locations, for groundwater flooding. There are three flood warning codes and a notification when warnings are removed. These are: - Severe Flood Warning: Severe flooding. Danger to life. - Flood Warning: Flooding is expected. Immediate action required. - Flood Alert: Flooding is possible. Be prepared. - Warning no longer in force: Flood warnings and flood alerts that have been removed in the last 24 hours. Live flood warnings in force are shown on GOV.UK and are available as a separate live feed on GOV.UK.

Listing of Severe Flood Warnings, Flood Warnings, Update Flood Warnings and Flood Alerts issued since the Floodline Warnings Direct service went live on January 26th 2006 to the present.

This dataset includes flood warnings issued by Natural Resources Wales (NRW) from 1 April 2013.

Flood Alerts and Warnings are issued for flooding from rivers and the sea. For Flood Alerts this is generally river catchments or stretches of coastline. For Flood Warnings and Severe Flood Warnings this is specific communities or parts of communities.

This record is for Approval for Access product AfA054 Flood Warning Areas. These are geographical areas where we expect flooding to occur and where we provide a Flood Warning Service. They generally contain properties that are expected to flood from rivers or the sea and in some areas, from groundwater. Specifically, Flood Warning Areas define locations within the Flood Warning Service Limit that represent a discrete community at risk of flooding.

Flood Warnings are issued when flooding is expected to occur, Severe Flood Warnings are issued to similar areas when there is a danger to life or widespread disruption is expected.

INFORMATION WARNING: Groundwater flood warning areas are property based, usually containing a discrete urban area, suburb, city, village, or hamlet and were created in various ways. In general specialists used the national groundwater dataset, historical maps, bedrock geology and records of properties affected by groundwater flooding in the past to create the groundwater flood warning areas. Additional data sources, including groundwater susceptibility maps, borehole data, local modelling and LiDAR may also have been used depending on the location of the area.

This dataset was last updated on July 9th 2025.

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This record is for Approval for Access product AfA054 Flood Warning Areas are geographical areas where we expect flooding to occur and where we provide a Flood Warning Service. They generally contain properties that are expected to flood from rivers or the sea and in some areas, from groundwater. Specifically, Flood Warning Areas define locations within the Flood Warning Service Limit that represent a discrete community at risk of flooding. A discrete community is a recognised and named geographical community, which can be an urban area, a significant suburb of a large city or a village or a hamlet. The purpose of Flood Warnings is to alert people that flooding is expected and they should take action to protect themselves and their property. Flood Warnings are issued when flooding is expected to occur, Severe Flood Warnings are issued to similar areas when there is a danger to life or widespread disruption is expected. INFORMATION WARNING: Groundwater flood warning areas are properties based, usually containing a discrete urban area, suburb, city, village or hamlet and were created in various ways. In general technical specialists used the national groundwater dataset, historical maps, bedrock geology and records of properties affected by groundwater flooding in the past to create the groundwater flood warning areas. Additional data sources, including groundwater susceptibility maps, borehole data, local modelling and LiDAR may also have been used depending on the location of the area. The triggers for Flood Warnings for groundwater flooding are based on actual observed groundwater levels. There are currently no flood risk maps for groundwater so our flood warning areas for groundwater tend to cover properties which we know have been flooded by groundwater in the past. Attribution statement: © Environment Agency copyright and/or database right 2015. All rights reserved.

The Ministry of Economic Affairs' Water Resources Agency's disaster emergency response team further combines rain, water level, reservoir and other real-time data, through computer technology calculations, providing real-time flood warnings for the public and relevant units. This allows the public to understand the risk of home flooding, prepare early, and reduce the occurrence of disasters. This dataset is linked to a Keyhole Markup Language (KML) file list, which is a markup language based on the XML syntax standard, used for geographical annotation. Documents written in the KML language are KML files, the same format as XML files, used in Google Earth related software for displaying geographical data. Many GIS-related systems now also use this format for the exchange of geographical data, with the KML format and encoding of this data being UTF-8.

The Numerical Flash Flood Alert APP (NFFA APP) proudly supports the water science community across the United States by offering streamlined access to essential flood data from all USGS stations.

Accessing water data can sometimes be challenging. Our website is designed to provide quick and easy access to vital flood information for all USGS stations, helping professionals and communities stay informed and prepared. Here’s what you can find:

Action stage: This crucial threshold helps signal when it's time to start taking action in response to potential flooding. Basin Area: Measured in square kilometers, this gives you insights into the scale of the potential flood. Basin slope and stream length: These key geographical features provide critical information on water flow and flood potential. Flashiness metrics: These indicators measure the variability in historical streamflow at each station, using a color-coded system: red indicates low variability, green is medium, and blue signifies high variability. Technological Expertise To deliver state-of-the-art solutions, we leverage a comprehensive suite of advanced IT tools:

Hydraulic & Hydrologic Modeling: We utilize sophisticated tools such as HEC-HMS for hydrology, HEC-RAS for hydraulics, and EF5 for precision in flash flood simulation. Our models are crucial for designing effective flood warning systems, enhanced by real-time satellite data to monitor and predict flood events accurately. Water Resources Management: Our application of WEAP aids in sustainable water resources planning across sectors like agriculture, urban centers, and treatment facilities. This tool supports our commitment to developing well-informed, sustainable management strategies through detailed numerical analysis. Pressurized Systems: Utilizing Pipe Flow Expert, we optimize systems for efficiency and sustainability, selecting the ideal pipes and pumps based on comprehensive hydrodynamic modeling. Data Analysis Software: We employ Python and R Studio for cutting-edge data analysis, allowing us to craft sophisticated algorithmic solutions that enhance our predictive capabilities and decision-making processes. GIS Software: Through ArcGIS and QGIS, we deliver intricate geographical mapping and spatial data analysis. These tools are integral to our comprehensive approach, offering crucial insights into the geographic dynamics of water flow and potential flood zones.

The nationwide flood warning in Norway became operational in 1989. The purpose is to avoid loss of life and values as a result of flooding, by preparing water flow forecasts and flood warnings that describe the level of care at the regional level (watercourses, county and/or group of municipalities). Flood warning API is based on REST. It delivers data such as XML and JSON (standard). Only GET is supported. There will be new versions of the API, so there is a version number in the link. We let old versions live for 6 months before they are deleted. API ' provides data in two formats, XML and JSON. JSON is the standard format if nothing is specified. But specifies by setting content type in request header The nationwide flood warning in Norway became operational in 1989. The purpose is to avoid loss of life and values as a result of flooding, by preparing water flow forecasts and flood warnings that describe the level of care at the regional level (watercourses, county and/or group of municipalities). Flood warning API is based on REST. It delivers data such as XML and JSON (standard). Only GET is supported. There will be new versions of the API, so there is a version number in the link. We let old versions live for 6 months before they are deleted. API ' provides data in two formats, XML and JSON. JSON is the standard format if nothing is specified. But specifies by setting content type in request header

Early event detection and response can significantly reduce the societal impact of floods. Currently, early warning systems rely on gauges, radar data, models and informal local sources. However, the scope and reliability of these systems are limited. Recently, the use of social media for detecting disasters has shown promising results, especially for earthquakes. Here, we present a new database for detecting floods in real-time on a global scale using Twitter. The method was developed using 88 million tweets, from which we derived over 10.000 flood events (i.e., flooding occurring in a country or first order administrative subdivision) across 176 countries in 11 languages in just over four years. Using strict parameters, validation shows that approximately 90% of the events were correctly detected. In countries where the first official language is included, our algorithm detected 63% of events in NatCatSERVICE disaster database at admin 1 level. Moreover, a large number of flood events not included in NatCatSERVICE are detected. All results are publicly available on www.globalfloodmonitor.org.

The Water Resources Agency's disaster emergency response team of the Ministry of Economic Affairs further combines real-time data such as rainfall, water level, and reservoir information with long-term disaster response experience and computer technology to provide reservoir alerts for the public and relevant units. This helps the public understand the risk of home flooding, prepare early, and reduce the occurrence of disasters. This dataset is linked to a Keyhole Markup Language (KML) file list. This format is a markup language based on the XML (eXtensible Markup Language) syntax standard, developed and maintained by Keyhole, a subsidiary of Google, to express geographic annotations. Documents written in the KML language are KML files, which use the XML file format and are used in Google Earth related software (Google Earth, Google Map, Google Maps for mobile...) to display geographic data (including points, lines, polygons, polyhedra, and models...). Many GIS-related systems now also use this format for the exchange of geographic data, and the fields and codes of this data are all in UTF-8.

This feature service depicts the National Weather Service (NWS) watches, warnings, and advisories within the United States. Watches and warnings are classified into 43 categories. Those 43 categories have been filtered to just coastal watches, warnings, and advisories: coastal flooding, hurricanes, tropical storms. A warning is issued when a hazardous weather or hydrologic event is occurring, imminent or likely. A warning means weather conditions pose a threat to life or property. People in the path of the storm need to take protective action.A watch is used when the risk of a hazardous weather or hydrologic event has increased significantly, but its occurrence, location or timing is still uncertain. It is intended to provide enough lead time so those who need to set their plans in motion can do so. A watch means that hazardous weather is possible. People should have a plan of action in case a storm threatens, and they should listen for later information and possible warnings especially when planning travel or outdoor activities.An advisory is issued when a hazardous weather or hydrologic event is occurring, imminent or likely. Advisories are for less serious conditions than warnings, that cause significant inconvenience and if caution is not exercised, could lead to situations that may threaten life or property.SourceNational Weather Service RSS-CAP Warnings and Advisories: Public AlertsNational Weather Service Boundary Overlays: AWIPS Shapefile DatabaseSample DataSee Sample Layer Item for sample data during Weather inactivity!Update FrequencyThe services is updated every 5 minutes using the Aggregated Live Feeds methodology.The overlay data is checked and updated daily from the official AWIPS Shapefile Database.Area CoveredUnited States and TerritoriesWhat can you do with this layer?Customize the display of each attribute by using the Change Style option for any layer.Query the layer to display only specific types of weather watches and warnings.Add to a map with other weather data layers to provide insight on hazardous weather events.Use ArcGIS Online analysis tools, such as Enrich Data, to determine the potential impact of weather events on populations.

The river height data is real-time operational data from automated telemetry systems and has not been quality controlled.The data is provided for flood warning purposes and most data will not be available during non flood periods.Most river height data is provided to the Bureau of Meteorology by other agencies. Separate approval may be required to use the data for other purposes.Additional river height data is available from the NSW Office of Water and from the NSW Department of Service Technology and Administration (Manly Hydraulics Laboratory).

Links to some of the Environment Agency Web Map Services (WMS) available. • EA Historic Flood Map • EA Flood Zone 3 • EA Flood Zone 2 • EA Flood Warning Areas

The EA Flood Warning Service operates in areas at risk of flooding from rivers and the sea. In select locations, the Environment Agency provides a groundwater flood warning/alert service in parts of England, targeted on communities that are known to be risk in chalk catchments, and have previously experienced groundwater flooding. This table details historical and current recorded flood alerts and warnings retrieved for areas in the East and West Midlands since 25/11/2022 included the flood alert area, date and time of the alert and the severity of the alert. Query for alerts and warnings is called hourly. To request access contact the Data Insight Team.

This dataset is available on Brisbane City Council’s open data website – data.brisbane.qld.gov.au. The site provides additional features for viewing and interacting with the data and for downloading the data in various formats.

Rainfall and Stream Height gauges owned by Brisbane City Council. This dataset contains the details for the telemetry sensors.

Council installs and maintains telemetry gauges at various locations across Brisbane as part of its hydrometric network. These gauges form part of the Bureau of Meteorology Flood Warning Network. This Brisbane City Council gauge information (raw data) is passed onto the Bureau of Meteorology which they display on their public website via various interfaces.

The hydrometric gauges:

• collect real-time information on water levels and rainfall
• provide information to trigger flood alerts and warnings
• provide information to trigger flooded road signage/flashing lights
• provide historic flood information for use in hydrology and hydraulic modelling.

The Data and resources section of this dataset contains further information for this dataset.

Road Closure Datahttps://gis.charleston-sc.gov/road-closures-regional/The city began capturing road closure data in October 2015 while responding to the 1000 year flood event. Since then, the City has been refining the process to capture and retain a history of city street closures. Emergency closures are reported based on field reports from first responders and city staff operating in the field. This data is used for situation awareness during flooding events by staff and the public This is not a detailed and complete survey of inundated roads. Not all flooding events are actively mapped and not all streets impacted are captured.This information should be used as a general information tool. Tide and Weather DataTide and weather data is collected and processed from NOAA sources and joined to the road closures using the closure start date and time. The process of calculating the joining the tide and weather data is experimental and subject to change.NOAA Weatherhttps://www.ncdc.noaa.gov/cdo-web/datasets/GHCND/stations/GHCND:USW00013782/detailNOAA tide data api (station=8665530)https://api.tidesandcurrents.noaa.gov/api/prod/ Fields STREET – Street name as recorded by the mapper REASON – Flood, Construction, Emergency, Warning SOURCE – CPD, etc. Type – Full, partial, warning ROADCLOSUREDATE - Start Datetime ROADCLOSUREEND - End Datetime INDIDENTDATE - Start Date (no time) YEAR – Start Date Year RoadClosureHours – Calculated (Hours between start and end) CommuteHours – Calculated (6AM-10AM = Morning Commute and 3PM-7PM= Evening Commute) TideDate - Nearest High / Low tide time and date MinsUntilTide – Calculated (minutes from start to nearest High / Low tide past or future) FloodRisk Calculated for nearest high / low tide: >=8 (Major), >= 7.5 (Moderate), and >=7 (Minor) NearestHighLowTide – MLLW height of nearest high or low tide MaxTide – Highest MLLW tide of the day TideType – Tide type of nearest high or low tide TideHeight - nearest 6 minute tide reading MoonPhase - moon phase in decimal MoonPhaseDesc - Calculated <=.05 or = 1 = New Moon, between .45 and .6 = Full Moon, else Other DailyPrecipitation _Downtown – Noaa DailyPrecipitationCat_Downtown – Calculated rain categories Fastest2minWindDirection_Downtown - wind direction bearing Fastest2minWindSpeed_Downtown Fastest2minWindDirectionDesc_Downtown – calculated directionals FloodReason_6MIN– Downtown NOAA weather and 6 minute tide categories. High Tide / Rain: Rain > =.5 and tide >= 6’ , Rain / Non-High Tide: Rain >= .5’ and tide type = low , High Tide / No Rain: Rain < .5 AND tide >= 6’ , No Rain/Low Tide:FloodReason_Day – Using NOAA Max high tide for the day EventName – event name for named events

This dataset contains the tweet IDs of 87,641,357 tweets related to floods in 11 languages collected between July 29, 2014 and November 20, 2018. All tweets mention one or more keywords in one of the respective languages: English: flood, floods, flooding, flooded, inundation, inundations, inundated Indonesian: banjir Filipino: baha, bumabaha, pagbaha French: inonder, inondation German: flut, hochwasser, Überflutung Italian: inondazione, alluvione Dutch: overstroming Polish: powódź, powodzie Portuguese: inundação, inundacão, inundaçao, inundacao, inundações Spanish: inundación, inundacion, inundar, inundaciones Turkish: su taşkın, su baskını, sel bastı, sel suyu, sel yüzünden, taşkın oldu, sel suyunun The Twitter statuses/lookup API supports retrieving the complete tweet object for a tweet ID (known as hydrating). Tools such as Twarc or Hydrator can be used to hydrate tweets. Per Twitter’s Developer Policy, while tweet IDs may be shared on behalf of an academic institution and for the sole purpose of non-commercial research, tweets may not. If you would like access, please file a request. Cite as: de Bruijn, J. A., de Moel, H., Jongman, B., de Ruiter, M. C., Wagemaker, J., & Aerts, J. C. (2019). A global database of historic and real-time flood events based on social media. Scientific Data, 6(1), 1-12. Questions about this dataset can be sent to j.a.debruijn at outlook dot com.

Rainfall and Stream Height gauges owned by Brisbane City Council. This is raw, unprocessed data.

Council installs and maintains telemetry gauges at various locations across Brisbane as part of its hydrometric network. These gauges form part of the Bureau of Meteorology Flood Warning Network. This Brisbane City Council gauge information (raw data) is passed onto the Bureau of Meteorology which they display on their public website via various interfaces.

The hydrometric gauges: collect real-time information on water levels and rainfall provide information to trigger flood alerts and warnings provide information to trigger flooded road signage/flashing lights provide historic flood information for use in hydrology and hydraulic modelling.

Automatically collected telemetry data for rainfall and stream height gauges owned by Brisbane City Council.

The dataset includes raw gauge readings in 5-minute increments covering a 24-hour rolling period. The data is updated every 10 minutes. Dataset includes gauge readings, descriptions and location details.

The Data and resources section of this dataset contains further information for this dataset.

Service Records and Retention System (SRRS) is historical digital data set DSI-9949, a collection of products created by the U.S. National Weather Service (NWS) and archived at the National Centers for Environmental Information (NCEI) [formerly National Climatic Data Center (NCDC)]. SRRS was a network of computers and associated hardware whose purpose was to transmit and store a large number of NWS products and make them available as needed. Basic meteorological and hydrological data, analyses, forecasts, and warnings are distributed among NWS offices over the AFOS (Automation of Field Operations and Services) communications system since 1978. These include PIREP (aircraft reports from pilots), AIRMET (aeronautical meteorological bulletins), SIGMET (significant meteorological information), surface and upper air plotted unanalyzed maps, air stagnation, precipitable water, Forecasts such as wind and temperature aloft, thickness and analysis, fire weather, area, local, zone, state, agricultural advisory, and terminal; and Warnings such as marine, severe weather, hurricane and tornado. The AFOS system was developed to increase the productivity and effectiveness of NWS personnel and to increase the timeliness and quality of their warning and forecasting services.

This format version of the SRRS data was archived at NCEI from 1983 to 2001 (when a new format was created). The NCEI can service requests for products from the SRRS; two types of products are available to the user: 1) graphic displays of meteorological analyses and forecast charts (limited), and 2) alphanumeric displays of narrative summaries and meteorological/hydrological data. The following is a partial list of historical SRRS products available through the NCDC: rawinsonde data above 100 MB; AIREPS buoy reports; coastal flood warning; Coast Guard surface report; climatological report (daily and misc, incl monthly reports); weather advisory Coastal Waters Forecast Center (CWSU); weather statement; 3- to 5-day extended forecast; average 6- to 10-day weather outlook (local and national); aviation area forecast winds aloft forecast; flash flood statements, watches and warnings; flood statement; flood warning forecast; medium range guidance; FOUS relative humidity/temperature guidance; FOUS prog max/min temp/POP guidance; FOUS wind/cloud guidance; Great Lakes forecast; hurricane local statement; high seas forecast; international aviation observations; local forecast; local storm report; rawinsonde observation - mandatory levels;, METAR formatted surface weather observation; marine weather statement; short term rorecast; non-precipitation warnings/watches/advisories; nearshore marine forecast (Great Lakes only), offshore aviation area forecast; offshore forecast; other marine products, other surface weather observations, pilot report plain language, ship report, state pilot report, collective recreational report; narrative radar summary radar observation; hydrology-meteorology data report; river summary; river forecast; miscellaneous river product; river recreation statement; ; regional weather summary; surface aviation observation; preliminary notice of watch and canc msg SVR; local storm watch and warning; cancelation msg SELS watch; point information message; state forecast discussion ; state forecast rawinsonde observation - significant levels; surface ship report at intermediate synoptic time; surface ship report at non-synoptic time; surface ship report at synoptic time; special weather statement international; SIGMET severe local storm watch and area outline; special marine warning; intermediate surface synoptic observation; main surface synoptic observation; severe thunderstorm warning; severe weather statement; severe storm outlook; narrative state weather summary; terminal forecast; tropical cyclone discussion; marine/aviation tropical cyclone advisory; public tropical cyclone advisory; tornado warning; transcribed weather broadcast; tropical weather discussion; tropical weather outlook and summary; AIRMET SIGMET zone forecast; terminal forecast (prior to 7/1/96); winter weather warnings, watches, advisories; marine advisory/warning; special marine warning; miscellaneous product convective SIGMET ; local ice forecast; area forecast discussion; public information statement. SRRS (DSI-9949) by the Gateway SRRS (DSI-9957; C00583). NWS products after 2001 can be obtained from those systems, from NCEI.

Flood hazard assessments have been carried out for several areas in the District. These include the Poverty Bay Flats, Gisborne urban area, and the Mangatuna/ Wharekaka Area for the Hikuwai/Uawa River. The flood hazard varies across liable areas. Generally towards the edge of the flooded area depths are shallow and floodwaters move at slow speeds. Therefore the degree of hazard is low. However floodwaters are generally deep and flow swiftly in the vicinity of the main river channel and other major flood flow paths. These areas generally have a high degree of flood hazard with silt and debris deposition. The process of assessing flood hazard, firstly involves a study into flood behaviour. This involves estimating discharge for the various sized floods and the determination of water levels, velocities and depth of flooding. Then secondly a design flood standard' is selected. The determination of thatdesign flood standard' balances the social, economic and ecological considerations against the consequences of flooding. If the standard is too low development will be inundated relatively frequently with greater damage. If the standard is too high land will incur unwarranted controls. The selection of the design flood standard depends on flood behaviour, landuse and consequences of larger floods. The level of protection offered by flood mitigation works may be different from the design flood standard adopted for land use planning. That level is dictated by economics of the situation or physical limitations of the site. It is prudent to assume that floods may occur greater than the ability of protection works to contain them. The design flood standard is intended to reduce the impacts of such floods, by avoiding or limiting development which would be affected.Flood Overlay categories includea) Flood Hazard Overlay 1 (River and Floodway): These are the main routes for floodwaters. They include all watercourses and adjacent berms liable to regular flooding. Floodwaters could be deep and fast flowing. These are areas unsuitable for regular human occupation. Floodway areas are areas which even if only partially blocked would cause a significant redistribution of flood flows. Care needs be taken not to alter the level of the land in a way which could divert floodwaters and cause adverse effects. Activities which could trap sediment in a flood and build up the river berms should also be avoided. b) Flood Hazard Overlay 2A (Moderate/High Hazard Areas): Similar to Flood Hazard Overlay 2 except that: i. ii. The flood hazard varies between “moderate” and “high”; and Flood warning systems and evacuation plans provide some measure of protection to residents Within this overlay some areas are unsuitable for permanent habitation, while others may be suitable subject to the practicality of evacuation routes and the potential numbers to be evacuated. c) Flood Hazard Overlay 2 (High Hazard Areas): Flooding in high hazard areas is associated with flow over stopbanks and roads and deep overland flow confined to narrow valleys. Floodwaters could cause structural damage to buildings and in extreme cases light framed houses could be swept away. Heavy silt deposition can occur. These areas are generally unsuitable for permanent habitation. Care needs be taken not to alter the level of the land in a way which could divert floodwaters and cause adverse effects. Activities which could trap sediment in a flood and build up the river berms should be avoided. d) Flood Hazard Overlay 3 (Flood Ponding Areas): This contains low-lying areas or basins subject to occasional but relatively deep flooding. Generally floodwaters would be slow moving or stationary. For Poverty Bay these areas have been flooded in 1985 and/or 1988. Ponding areas store floodwaters during major rainfall events. Infilling of these areas may divert and raise the level of floodwaters elsewhere. e) Flood Hazard Overlay 4 (Areas Liable to Flooding): contains areas on floodplains that have previously been flooded. For Poverty Bay that is flooding from the 1985 and/or 1988 floods. For the Mangatuna/ Wharekaka area it is flooding from the 1988 flood. For the Waimata Taruheru and Turanganui Rivers and the Waikanae Creek it is flooding from the 1977 and/or 1985 flood. f) Flood Hazard Overlay 5 (Flood Fringe Areas): contains areas that have not previously flooded but are expected to be flooded under design flood standard conditions. Generally water would be shallow and slow moving. These areas are generally suitable for permanent habitation as flooding should not cause structural damage. However floor levels need to be high enough for inhabitants to remain safely in houses until effective evacuation can take place. Care needs be taken not to alter the level of the land in a way which could divert floodwaters and cause adverse effects. g) Flood Hazard Overlay 6 (Old River Loops): These areas are old river loops that can be flooded to depths exceeding 1m. They are not generally suitable for residential occupation because the depth of water could cause difficulties in evacuation. Care needs be taken not to alter the level of the land in a way which could divert floodwaters and cause adverse effects. h) Flood Hazard Overlay 7 (Urban Stormwater Flood Hazard Area): These areas are affected by flooding from local streams and drains in design flood conditions. The stormwater reticulation system within the Gisborne urban area is presently undergoing an upgrading programme and the extent of this area may be able to be reduced when this programme is complete. However, work on this has only just begun and therefore the 1977 and 1985 floodspread maps are to be used until then as the basis of this overlay area. i) Flood Hazard Overlay 8 (Urban Ponding Areas): Urban ponding areas store floodwaters during major rainfall events. Infilling of these areas would put extra stress on urban reticulation systems or require expensive upgrading of such systems. j) Flood Hazard Overlay 9 (Urban Floodways): These are main routes for floodwaters. They include all rivers, streams and watercourses and adjacent berms liable to flooding. Floodwaters could be deep and fast flowing. Floodway areas are areas which even if partially blocked would cause a significant redistribution of flood flows. Care needs to be taken not to cause adverse effects by diverting or impeding floodwaters.