CMAP has developed a Stormwater and Flooding strategy paper, which will inform the recommendations made in ON TO 2050 to address urban and riverine flooding. The paper presents strategies to reduce flooding impact throughout the region by integrating stormwater management into transportation and land use planning, alongside analysis of damages from past flooding events. To help direct these strategies, CMAP has developed urban and riverine Flooding Susceptibility Indexes (FSIs) to identify priority areas across the region for flooding mitigation activities. GIS datasets representing flood susceptibility factors were used to construct the indexes, by assessing each factor’s influence using a GIS-based frequency ratio approach. The approach, inputs, and results are described in greater detail in the technical appendix of the strategy paper. The values contained within the raster attribute table represent low (1) to high (10) flood susceptibility. The inputs are listed below, alongside their sources:Reported Flood Locations: FEMA National Flood Insurance Program Claims, FEMA Individual Assistance Grants, FEMA Discovery Data, City of Chicago 311 Standing Water Locations, MWRD Detailed Watershed Plans, DuPage County GIS, Kendall County Department of Planning, Lake County Stormwater Management Commission.Topographic Wetness Index: CMAP analysis of Illinois State Geological Survey (ISGS) Light Detection and Ranging (LiDAR) data.Combined sewer service areas: Metropolitan Water Reclamation District; IL EPA; municipalities with combined sewers outside of Cook County.Elevation differential between property and nearest Base Flood Elevation (BFE): CMAP analysis of ISGS LiDAR data and FEMA BFE data.Impervious cover: 2011 National Land Cover Dataset.Impervious cover of watershed catchment: CMAP analysis of NLCD and National Hydrography Program data.Age of first development: U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Wall-to-Wall Anthropogenic Land Use Trends (NWALT) 1974-2012 land cover.Precipitation variation: NOAA Atlas 14 10-year, two hour storm event.

Using the roofprint data from MassGIS as of June 2020, the MVC converted those roofprints to centroids. Only structures having a roofprint area >400sq ft were included in the analysis. This was done to eliminate presumed sheds, garages, and small barns, from the analysis. The structure points were analyzed against the natural hazard spatial coverages to identify those structures that are at risk. The 5 hazards are Wildfire, FEMA Flood, Sea Level Rise, Tsunami, and Hurricane. For those hazards with varying levels of impact, the specific level is noted in the attribute table.Hazard Data Sources:Wildfire Risk Area -- MVC 2020; Process: Any pitch pine and scrub/shrub oak habitats were extracted from their larger dataset (TNC 2002). The other 2 files are extracts from the MassGIS Land Use/Land Cover data of 2016. From that dataset I took Land Cover Class 9 (deciduous) & Class 10 (Evergreen) where General Use was any of the following: 2, 6, 7, 8, 9, OR Detailed Use was 39*, 13*, 44*. Lands fitting that criteria definition were dissolved together but only where contiguous. Then, any areas within that which were 50 acres or more were retained. Lastly, that file was buffered 1000ft.So, any structures within the a) pitch pine/scrub oak habitat; OR b) contiguous woodland; OR c) within 100ft of contiguous woodland are considered within the ‘Wild & Urban Land Interface’ (or within an area which is at risk of being negatively impacted by wildfire).Those 4 datalayers were dissolved together into this spatial extent.Tsunami-- MVC 2020; Area is 1 mile from the MassDEP/MassGIS 1:25,000 hydrology coastlineFEMA Flood -- FEMA Effective 2016Hurricane- SLOSH model by NOAA/USACE 2013Sea Level Rise - Flood Risk Model -MassDOT/Woods Hole Group/UMass Boston 2020 -- Flood Risk Model with flooding probability for 'present' timestamp (represents year 2013), and forecasts for 2030, 2050, and 2070. Similar timestamp forecasts for modeled flooding depth during 100year storm event.

WWNP Floodplain Woodland Planting Potential is our best estimate of locations where tree planting on the floodplain may be possible, and effective to attenuate flooding. The dataset is designed to support signposting of areas of floodplain not already wooded. The dataset is based upon fluvial Flood Zone 2 of the Flood Map for Planning. A set of open access constraints data was used to erase areas which contained existing woodland, watercourses, peat, roads, rail and urban locations.The information provided is largely based on modelled data and open constraints data, and is therefore indicative rather than specific. Locations identified may have more recent building or land use than available data indicates. It is important to note that land ownership and change to flood risk have not been considered, and it may be necessary to model the impacts of significant planting.The Environment Agency’s Flood Map for Planning (2016) - Flood Zone 2 (0.1% AEP) was used to delineate areas close to the watercourse in the floodplain which may be suitable for tree planting. The ‘Woodland Constraints’ data was then applied, masking existing woodland, watercourses, peat, roads, rail and urban areas.

The identification of areas with significant flood risk (TRI) is based on the results of the Preliminary Flood Risk Assessment (EPRI), carried out at the level of each river basin district. It is also based on the national criteria for characterising the importance of the flood risk, as defined in the Ministerial Order of 27 April 2012, and takes into account, where appropriate, local particularities, such as the dangerous nature of the flood and any other local factors likely to aggravate the potential negative consequences associated with floods for human health, the environment, property including cultural heritage and economic activity. The list of IRRs drawn up by the competent authority at this scale, the Basin Coordinating Prefect. With a high urban population density, IRRs receive special attention from public authorities to reduce the cost of flood damage. To this end, the 15 TRIs identified in 2012 (cycle 1 of the Flood Directive) in the Greater East region are subject to: — a mapping of the risks to flood phenomena characterising the territory; — local flood risk management strategies at the level of the watersheds concerned Of the 15 TRIs in the Grand East region, 12 are concerned by the Rhine-Meuse basin and 3 by the Seine-Normandie basin. A “DISTRICT” field has been added to the GIS layer so that the different river basin districts including IRRs can be discerned.

This site provides access to download an ArcGIS geodatabase or shapefiles for the 2017 Texas Address Database, compiled by the Center for Water and the Environment (CWE) at the University of Texas at Austin, with guidance and funding from the Texas Division of Emergency Management (TDEM). These addresses are used by TDEM to help anticipate potential impacts of serious weather and flooding events statewide. This is part of the Texas Water Model (TWM), a project to adapt the NOAA National Water Model [1] for use in Texas public safety. This database was compiled over the period from June 2016 to December 2017. A number of gaps remain (towns and cities missing address points), see Address Database Gaps spreadsheet below [4]. Additional datasets include administrative boundaries for Texas counties (including Federal and State disaster-declarations), Councils of Government, and Texas Dept of Public Safety Regions. An Esri ArcGIS Story Map [5] web app provides an interactive map-based portal to explore and access these data layers for download.

The address points in this database include their "height above nearest drainage" (HAND) as attributes in meters and feet. HAND is an elevation model developed through processing by the TauDEM method [2], built on USGS National Elevation Data (NED) with 10m horizontal resolution. The HAND elevation data and 10m NED for the continental United States are available for download from the Texas Advanced Computational Center (TACC) [3].

The complete statewide dataset contains about 9.28 million address points representing a population of about 28 million. The total file size is about 5GB in shapefile format. For better download performance, the shapefile version of this data is divided into 5 regions, based on groupings of major watersheds identified by their hydrologic unit codes (HUC). These are zipped by region, with no zipfile greater than 120mb: - North Tx: HUC1108-1114 (0.52 million address points) - DFW-East Tx: HUC1201-1203 (3.06 million address points) - Houston-SE Tx: HUC1204 (1.84 million address points) - Central Tx: HUC1205-1210 (2.96 million address points) - Rio Grande-SW Tx: HUC2111-1309 (2.96 million address points)

Additional state and county boundaries are included (Louisiana, Mississippi, Arkansas), as well as disaster-declaration status.

Compilation notes: The Texas Commission for State Emergency Communications (CSEC) provided the first 3 million address points received, in a single batch representing 213 of Texas' 254 counties. The remaining 41 counties were primarily urban areas comprising about 6.28 million addresses (totaling about 9.28 million addresses statewide). We reached the GIS data providers for these areas (see Contributors list below) through these emergency communications networks: Texas 9-1-1 Alliance, the Texas Emergency GIS Response Team (EGRT), and the Texas GIS 9-1-1 User Group. The address data was typically organized in groupings of counties called Councils of Governments (COG) or Regional Planning Commissions (RPC) or Development Councils (DC). Every county in Texas belongs to a COG, RPC or DC. We reconciled all counties' addresses to a common, very simple schema, and merged into a single geodatabase.

November 2023 updates: In 2019, TNRIS took over maintenance of the Texas Address Database, which is now a StratMap program updated annually [6]. In 2023, TNRIS also changed its name to the Texas Geographic Information Office (TxGIO). The datasets available for download below are not being updated, but are current as of the time of Hurricane Harvey.

References: [1] NOAA National Water Model [https://water.noaa.gov/map] [2] TauDEM Downloads [https://hydrology.usu.edu/taudem/taudem5/downloads.html] [3] NFIE Continental Flood Inundation Mapping - Data Repository [https://web.corral.tacc.utexas.edu/nfiedata/] [4] Address Database Gaps, Dec 2017 (download spreadsheet below) [5] Texas Address and Base Layers Story Map [https://www.hydroshare.org/resource/6d5c7dbe0762413fbe6d7a39e4ba1986/] [6] TNRIS/TxGIO StratMap Address Points data downloads [https://tnris.org/stratmap/address-points/]

This dataset contains a digital urban scenario, named Tomorrowville, that is developed as a testbed for multi-hazard risk assessments and to evaluate the performance of urbanisation scenarios. Tomorrowville was created to represent a global-south urban setting by means of its socio-economic and physical aspects. It covers an area of 500ha located south of Kathmandu (Nepal). The dataset consists of 5 different data types: - Buildings: Data representing the building footprints for today and 50 years from now including specific attributes to be used within multi-hazard risk assessments. - Land uses: Data representing the land use information for today and 50 years from now. - Vulnerability: Tabular files that contain vulnerability functions for buildings under earthquake and flood hazards. - Household: Data that contains social attributes of the Tomorrowville, such as the level of education, age, gender and working status of the individuals and their states in the households. - Hazards: Data representing the hazards (earthquake (eq), floods (fl) and debris flows (df) that may impact the case study areas of Tomorrowville. Observational data of the built environment and socio-economical properties of Kathmandu and Nairobi were used in addition to synthetic social data to create the initial scenario. This is a synthetic social dataset, meaning it was derived from existing population projections and distributions for the testbed but does not reflect the reality on the ground. It is synthetically created using specific algorithms in a GIS environment to represent a Global South social context. For the building data, Open Street Map (OSM) database is used as a basis. The data is scraped from OSM and modified to represent an urban context for Tomorrowville. The attributes are also modified to be able to use in a multi-hazard risk computation. A taxonomy string is generated for each building that represents an acronym for its building code level, number of storeys, occupation type and structural system. The hazards that were existing in the selected spatial extent were earthquake, flood, and debris flow. Hazard data represents an intensity measure for the relevant hazard type (ground acceleration for earthquake, flow velocity for the flood and debris flow hazards). The following hazard input data are included: - For the flood simulations, the discharge and rainfall time series are generated based on moderate to peak daily data based on recorded data from the Department of Hydrology and Meteorology, Nepal. - Earthquake hazard sources are generated and simulated by Jenkins et al. (2023). - For the debris-flow and flood simulations tri-stereo Pleiades satellite imagery is used to produce a 2m resolution Digital Elevation Model. The work to create this dataset is supported by NERC as part of the GCRF Urban Disaster Risk Hub (NE/S009000/1)

Much of the settled Hawke’s Bay region is low lying and built on river flood plains. This brings the risk of flooding, which is our most common natural hazard - a severe storm or flood happens every 10 years on average. Major storms affect wide areas and can be accompanied by strong winds, heavy rain or snowfall, thunder, lightning, and rough seas. They can cause damage to property and infrastructure, affect crops and livestock, disrupt essential services and cause coastal inundation.Rivers normally flood every winter when a storm brings more rainwater than can soak into the soil. When floods threaten communities the flood become a hazard. In Hawke's Bay stop banks have been built alongside many of the rivers to hold in the extra flood water. However in a severe storm, rivers could breach stop banks and the flood waters may go through farms, homes, shops, schools and damage roads and other infrastructure.There have been significant flood protection systems completed on the Heretaunga Plains and the Ruataniwha Plains. Flood protection works in Hawke’s Bay are generally designed to contain a 1% annual exceedance probability (AEP) flood). These works have significantly reduced the effect of small to medium sized floods, but a large flood could overwhelm the works and have a devastating effect. Such a flood, which exceeds the design capacity of the flood protection system, is called a Super Design Flood. Flooding from localised downpours in urban areas can also overwhelm drainage systems, so events below the AEP can still be costly.With climate change, rainfall patterns in the Hawke’s Bay are expected to change over the next century; winters are predicted to become drier, but overall flood risk is expected to increase as single events may be more intense.

This dataset has been produced as part of the Mapping Potential for Working with Natural Processes research project (SC150005). The project created a toolbox of mapped data and methods which enable operational staff in England to identify potential locations for Working with Natural Processes (WWNP).

Data has been produced for each intervention covered by the project. The final outputs include the following datasets: • Floodplain Woodland Planting Potential • Riparian Woodland Planting Potential • Wider Catchment Woodland • Floodplain Reconnection Potential • Runoff Attenuation Features 3.3% AEP • Runoff Attenuation Features 1% AEP • Woodland Constraints

WWNP Riparian Woodland Potential is our best estimate of locations where tree planting may be possible on smaller floodplains close to flow pathways, and effective to attenuate flooding. The dataset is designed to support signposting of riparian areas not already wooded. The dataset is based upon a 50m buffer of available OS Open Data river networks. A set of open access constraints data was used to erase areas which contained existing woodland, watercourses, peat, roads, rail and urban locations.

The information provided is largely based on open data, and is indicative rather than specific. Locations identified may have more recent building or land use than available data indicates. It is important to note that land ownership and change to flood risk have not been considered, and it may be necessary to model the impacts of significant planting.

Further information on the Working with Natural Processes project, including a mapping user guide, can be found in the reports published here:

https://www.gov.uk/government/publications/working-with-natural-processes-to-reduce-flood-risk㴽

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.

The 2021 National Hydrologic Assessment offers an analysis of flood risk, water supply, and ice break-up and jam flooding for spring 2021 based on late summer, fall, and winter precipitation, frost depth, soil saturation levels, snowpack, current streamflow, and projected spring weather. NOAA's network of 122 Weather Forecast Offices, 13 River Forecast Centers, National Water Center, and other national centers nationwide assess this risk, summarized here at the national scale. Overall, a reduced risk of spring flooding exists this year primarily due to dry fall and winter, along with limited snow still remaining on the ground. Major flooding is not expected this spring season. Minor to moderate flooding is ongoing across portions of the Lower Missouri River Basin with the flood risk predicted to continue through spring. The exception to the reduced risk is over the Coastal Plain of the Carolinas and Lower Ohio River Basin where flooding is predicted this spring, driven by above normal precipitation over the winter months, which has led to ongoing elevated streamflows and flooding and highly saturated soil conditions. This wet pattern is expected to continue across the Coastal Plain of the Carolinas and Lower Ohio River Basin through spring. It is important to note that heavy rainfall at any time can lead to flooding, even in areas where overall risk is considered low. This assessment addresses only spring flood potential on the timescale of weeks to months, not days or hours. Debris flow and flash flooding often associated with burn scars and urban areas can form quickly and occur any time with heavy rainfall events. Nearly every day, flooding happens somewhere in the United States or its territories. Flooding can cause more damage than any other weather-related event...with an annual average direct damage impact of 8 billion dollars a year over the past 40 years, with these impact costs adjusted for inflation. Flooding is one of America's most underrated killers, causing nearly 100 fatalities per year… roughly half of which occur in vehicles. Flowing water can be particularly powerful and dangerous… with just six inches of water able to sweep a person off their feet… and two feet of rushing water able to carry a mid-size car downstream. No vehicle should ever attempt to cross a flooded roadway, and drivers are reminded to “Turn Around, Don’t Drown.” To be prepared, every American should know their flood risk and what to do before, during, and after a flood event. This information is available at www.ready.gov/floods. To remain apprised of your current flood risk, visit weather.gov for the latest official watches and warnings. For detailed hydrologic conditions and forecasts, go to water.weather.gov.

This web layer contains data of state level flood damage in India (2016 - 2018) and contains information about area affected (Mha) in 2016, population affected (Million) in 2016, area wise (Mha) damages to Crops in 2016, value wise (Rs. Crore) damages to Crops in 2016 etc.Floods in IndiaFloods are recurrent phenomena in India. Due to different climatic and rainfall patterns in different regions, it has been the experience that, while some parts are suffering devastating floods, another part is suffering drought at the same time. With the increase in population and development activity, there has been a tendency to occupy the floodplains, which has resulted in damage of a more serious nature over the years. Often, because of the varying rainfall distribution, areas which are not traditionally prone to floods also experience severe inundation. Thus, floods are the single most frequent disaster faced by the country.Flooding is caused by the inadequate capacity within the banks of the rivers to contain the high flows brought down from the upper catchments due to heavy rainfall. Flooding is accentuated by erosion and silting of the riverbeds, resulting in a reduction of the carrying capacity of river channels; earthquakes and landslides leading to changes in river courses and obstructions to flow; synchronization of floods in the main and tributary rivers; retardation due to tidal effects; encroachment of floodplains; and haphazard and unplanned growth of urban areas. Some parts of the country, mainly coastal areas of Andhra Pradesh, Orissa, Tamil Nadu and West Bengal, experience cyclones, which are often accompanied by heavy rainfall leading to flooding.Flood report2016 Assam floods: Heavy rains in July–August resulted in floods affecting 1.8 million people and flooding the Kaziranga National Park killing around 200 wild animals. 2017 Gujarat flood: Following heavy rain in July 2017, Gujarat state of India was affected by the severe flood resulting in more than 200 deaths. August 2018 Kerala Flood: Following high rain in late August 2018 and heavy Monsoon rainfall from August 8, 2018, severe flooding affected the Indian state of Kerala resulting over 445 deaths.The attributes are given below for this web map:Area Affected (Mha) in 2016Population Affected (Million) in 2016Area Wise (Mha) Damages to Crops in 2016Value Wise (Rs. Crore) Damages to Crops in 2016No. of Houses Damaged in 2016Value (Rs. Crore) of Houses Damaged in 2016No. of Cattle Lost in 2016No. of Human Lives Lost in 2016Damage to Public Utilities (Rs. Crore) in 2016Total Damages - Crops, Houses, & Public Utilities (Rs. Crore) in 2016Area Affected (Mha) in 2017Population Affected (Million) in 2017Area Wise (Mha) Damages to Crops in 2017Value Wise (Rs. Crore) Damages to Crops in 2017No. of Houses Damaged in 2017Value (Rs. Crore) of Houses Damaged in 2017No. of Cattle Lost in 2017No. of Human Lives Lost in 2017Damage to Public Utilities (Rs. Crore) in 2017Total Damages - Crops, Houses & Public Utilities (Rs. Crore) in 2017Area Affected (Mha) in 2018Population Affected (Million) in 2018Area Wise (Mha) Damages to Crops in 2018Value Wise (Rs. Crore) Damages to Crops in 2018No. of Houses Damaged in 2018Value (Rs. Crore) of Houses Damaged in 2018No. of Cattle Lost in 2018No. of Human Lives Lost in 2018Damage to Public Utilities (Rs. Crore) in 2018Total Damages - Crops, Houses, & Public Utilities (Rs. Crore) in 2018This web layer is offered by Esri India, for ArcGIS Online subscribers. If you have any questions or comments, please let us know via content@esri.in.

The Nature Conservancy and Texas A&M AgriLife Extension completed the Green Stormwater Infrastructure for Urban Resilience: Opportunity Analysis for Dallas, Texas in collaboration with the City of Dallas and The Trust for Public Land, to identify areas in Dallas where green stormwater infrastructure can most effectively enhance urban flood management – considering capacity, cost, and future impacts of climate change. The focus was on evaluating opportunities where the existing drainage network may be limited, and likely to lead to areal flooding.The priority subwatersheds and GSI opportunity layers included here are outputs from modeling and spatial analysis, which have inherent limitations and uncertainties [1]. We share these layers to facilitate community, policy, and investment considerations, and recommend they be considered together with additional data, such as: City data on channel flooding, customer service calls and upcoming streets and parks projects; FEMA floodplain maps and Community Rating System scores; and data on water quality, equity and land use types available within The Trust for Public Land’s Smart Growth for Dallas tool [2]. Data from this analysis has been integrated into TPL’s Smart Growth for Dallas Decision Support Tool.Priority Subwatersheds. These subwatersheds represent priority areas where GSI could improve stormwater drainage. These areas drain to stormwater network inlets that overflowed in study models* under a variety of rainfall events and indicate where the drainage network is undersized and likely to contribute to aerial flooding. These areas do not represent areal flood risk. (*modeled using EPA SWMM v 5.1.; see analysis sections 2.1-2.3 and 3.2).Green Stormwater Infrastructure (GSI) Opportunity Areas, for the 100-year current conditions storm. The GSI opportunity areas identified are high level and focus on the three types of GSI systems included in the study: bioretention areas, rain gardens, and rainwater harvesting cisterns falling within priority subwatersheds for current conditions storms. Opportunities exist outside of these areas and for other types of GSI. Furthermore, additional detailed feasibility studies would be required for any potential site.