Layer used in public web app https://niwa.maps.arcgis.com/apps/webappviewer/index.html?id=933e8f24fe9140f99dfb57173087f27d to provide Flood Estimation for New Zealand 1. Modelled flood frequency estimates on river lines.NZREACH NZ digital network 1 ID no.River name where availableAreakm2 catchment area draining to the downstream end of this reach (square kilometres)q100_reach ratio of Q100 (1% aep flood) to mean annual floodH&C18_MAF mean annual flood (cumecs)H&C18_5-yr 5-yr (20% aep) flood (cumecs)H&C18_10y 10-yr (10% aep) flood (cumecs)H&C18_20y 20-yr (5% aep) flood (cumecs)H&C18_50y 50-yr (2% aep) flood (cumecs)H&C18_100y 100-yr (1% aep) flood (cumecs)H&C18_1000y 1000-yr (0.1% aep) flood (cumecs)HCse_MAF standard error of mean annual flood (cumecs)HCse_5y standard error of 5-yr (20% aep) flood (cumecs)HCse_10y standard error of 10-yr (10% aep) flood (cumecs) HCse_20y standard error of 20-yr (5% aep) flood (cumecs)HCse_50y standard error of 50-yr (2% aep) flood (cumecs)HCse_100y standard error of 100-yr (1% aep) flood (cumecs)HCse_1000y standard error of 1000-yr (0.1% aep) flood (cumecs)Strm_Order Strahler stream order (1=headwater, two ones join to make an order 2, etc.) 2. 2. At-site flood statistics at flow recorders used in the model development

Siteno NIWA reference number for flow recorder Name Flow recorder name generally 'river' at 'location' NZTM_E NZTM easting NZTM_N NZTM northingRegion Regional council or unitary authority territoryOperator Organisation that oprates the flow recorder Funder Organisation that funds the flow recorder (can be more than one)Area_km2 catchment area draining to the flow recorder (square kilometers)No_years Number of years in the annual flood series (allowing for years with missing data)L1_mean Mean of the annual flood series (linear moment 1)L2 Linear moment 2 of the annual flood series (analogous to standard deviation)Lcv Linear CV of the annual flood series (L2/L1) T3_Lskew Linear skew ratio of the annual flood series T4_Lkurt Linear kurtosis ratio of the annual flood series Gumb_u Gumbel distribution u of the annual flood series Gumb_alpha Gumbel distribution alpha of the annual flood series GEV_u Generalised Extreme Value u of the annual flood seriesGEV_alpha Generalised Extreme Value alpha of the annual flood series GEV_k Generalised Extreme Value k of the annual flood series GEV_z Hosking-Wallis normal standard variate to test significance of GEV-k (is the at-site distribution Gumbel or not?)Data 2.33y mean annual flood (2.33-yr assuming Gumbel, or 43% aep)Data 5y 5-yr (20% aep) flood (cumecs)Data 10y 10-yr (10% aep) flood (cumecs)Data 20y 20-yr (5% aep) flood (cumecs)Data 50y 50-yr (2% aep) flood (cumecs)Data 100y 100-yr (1% aep) flood (cumecs)Data 250y 250-yr (0.4% aep) flood (cumecs)Data 500y 500-yr (0.2% aep) flood (cumecs) Data 1000y 1000-yr (0.1% aep) flood (cumecs)se_2.33y standard error of mean annual flood (%) se_5y standard error of 5-yr (20% aep) flood (%)se_10y standard error of 10-yr (10% aep) flood (%)se_20y standard error of 20-yr (5% aep) flood (%)se_50y standard error of 50-yr (2% aep) flood (%)se_100y standard error of 100-yr (1% aep) flood (%)se_250y standard error of 250-yr (0.4% aep) flood (%)se_500y standard error of 500-yr (0.2% aep) flood (%) se_1000y standard error of 1000-yr (0.1% aep) flood (%)

1. Return period estimates of the area-rain intensity values for small catchments. Where results display '-1' the catchment is greater than 30 square kilometres and no answer is available. Numbers need to be multiplied by the Rational Method 'C' factor to give the required flood magnitude. NZREACH NZ digital network 1 ID no. AREA_km2 catchment area draining to the flow recorder (square kilometers)QIA_5y 5-yr (20% aep) IA estimateQIA_10y 10-yr (10% aep) IA estimate QIA_20y 20-yr (5% aep) IA estimateQIA_50y 50-yr (2% aep) IA estimateQIA_100y 100-yr (1% aep) IA estimate QIA_1000y 1000-yr (0.1% aep) IA estimate4. Annual data values at flow recorders used in the model development. Layer coming later.Spatial Reference: New Zealand Transverse Mercator (NZTM) EPSG:2193 (2193) XMin: 1090154.6277 YMin: 4748852.6367 XMax: 2089112.8753000004 YMax: 6193369.0554_Item Page Created: 2019-03-15 05:14 Item Page Last Modified: 2025-04-05 20:42Owner: NIWA_OpenData

A map service and web application where users can extract flood statistics from a regional flood model, at-site flood statistics and annual maximum flows from flow recorders used in the model development, flood estimates based on rain intensity for use in the Rational Method. 1. Modelled flood frequency estimates on river lines.NZREACH NZ digital network 1 ID no.River name where availableAreakm2 catchment area draining to the downstream end of this reach (square kilometres)q100_reach ratio of Q100 (1% aep flood) to mean annual floodH&C18_MAF mean annual flood (cumecs)H&C18_5-yr 5-yr (20% aep) flood (cumecs)H&C18_10y 10-yr (10% aep) flood (cumecs)H&C18_20y 20-yr (5% aep) flood (cumecs)H&C18_50y 50-yr (2% aep) flood (cumecs)H&C18_100y 100-yr (1% aep) flood (cumecs)H&C18_1000y 1000-yr (0.1% aep) flood (cumecs)HCse_MAF standard error of mean annual flood (cumecs)HCse_5y standard error of 5-yr (20% aep) flood (cumecs)HCse_10y standard error of 10-yr (10% aep) flood (cumecs) HCse_20y standard error of 20-yr (5% aep) flood (cumecs)HCse_50y standard error of 50-yr (2% aep) flood (cumecs)HCse_100y standard error of 100-yr (1% aep) flood (cumecs)HCse_1000y standard error of 1000-yr (0.1% aep) flood (cumecs)Strm_Order Strahler stream order (1=headwater, two ones join to make an order 2, etc.) 2. 2. At-site flood statistics at flow recorders used in the model development

Siteno NIWA reference number for flow recorder Name Flow recorder name generally 'river' at 'location' NZTM_E NZTM easting NZTM_N NZTM northingRegion Regional council or unitary authority territoryOperator Organisation that oprates the flow recorder Funder Organisation that funds the flow recorder (can be more than one)Area_km2 catchment area draining to the flow recorder (square kilometers)No_years Number of years in the annual flood series (allowing for years with missing data)L1_mean Mean of the annual flood series (linear moment 1)L2 Linear moment 2 of the annual flood series (analogous to standard deviation)Lcv Linear CV of the annual flood series (L2/L1) T3_Lskew Linear skew ratio of the annual flood series T4_Lkurt Linear kurtosis ratio of the annual flood series Gumb_u Gumbel distribution u of the annual flood series Gumb_alpha Gumbel distribution alpha of the annual flood series GEV_u Generalised Extreme Value u of the annual flood seriesGEV_alpha Generalised Extreme Value alpha of the annual flood series GEV_k Generalised Extreme Value k of the annual flood series GEV_z Hosking-Wallis normal standard variate to test significance of GEV-k (is the at-site distribution Gumbel or not?)Data 2.33y mean annual flood (2.33-yr assuming Gumbel, or 43% aep)Data 5y 5-yr (20% aep) flood (cumecs)Data 10y 10-yr (10% aep) flood (cumecs)Data 20y 20-yr (5% aep) flood (cumecs)Data 50y 50-yr (2% aep) flood (cumecs)Data 100y 100-yr (1% aep) flood (cumecs)Data 250y 250-yr (0.4% aep) flood (cumecs)Data 500y 500-yr (0.2% aep) flood (cumecs) Data 1000y 1000-yr (0.1% aep) flood (cumecs)se_2.33y standard error of mean annual flood (%) se_5y standard error of 5-yr (20% aep) flood (%)se_10y standard error of 10-yr (10% aep) flood (%)se_20y standard error of 20-yr (5% aep) flood (%)se_50y standard error of 50-yr (2% aep) flood (%)se_100y standard error of 100-yr (1% aep) flood (%)se_250y standard error of 250-yr (0.4% aep) flood (%)se_500y standard error of 500-yr (0.2% aep) flood (%) se_1000y standard error of 1000-yr (0.1% aep) flood (%)

1. Return period estimates of the area-rain intensity values for small catchments. Where results display '-1' the catchment is greater than 30 square kilometres and no answer is available. Numbers need to be multiplied by the Rational Method 'C' factor to give the required flood magnitude. NZREACH NZ digital network 1 ID no. AREA_km2 catchment area draining to the flow recorder (square kilometers)QIA_5y 5-yr (20% aep) IA estimateQIA_10y 10-yr (10% aep) IA estimate QIA_20y 20-yr (5% aep) IA estimateQIA_50y 50-yr (2% aep) IA estimateQIA_100y 100-yr (1% aep) IA estimate QIA_1000y 1000-yr (0.1% aep) IA estimate4. Annual data values at flow recorders used in the model development. Layer coming later.

_Item Page Created: 2018-07-08 23:41 Item Page Last Modified: 2025-04-05 20:46Owner: NIWA_OpenData

NZ Local River Names (based on REC2) Layer can be used to display New Zealand rivers and their names.The River Environment Classification (REC) is a database of catchment spatial attributes, summarised for every segment in New Zealand's network of rivers. The attributes were compiled for the purposes of river classification. Examples where the REC can be used include, catchment rainfall calculations, catchment river flows, flood forecasting, land use and catchment associations.CreationThe REC was originally created using hydrological networking tools and a digital elevation model.River names have been attached where available.REC2 (River Environment Classification, v2.5) - June 2019 [Hosted Feature Layer]This service depicts rivers as linesThe River Environment Classification (REC) is a database of catchment spatial attributes, summarised for every segment in New Zealand's network of rivers. The attributes were compiled for the purposes of river classification, while the river network description has been used to underpin models. Typically, models (e.g. CLUES and TopNet) would use the dendritic (branched) linkages of REC river segments to perform their calculations. Since its release and use over the last decade, some errors in the location and connectivity of these linkages have been identified. The current revision corrects those errors, and updates a number of spatial attributes with the latest data. REC2 provides a re-cut framework of rivers for modelling and classification. It is built on a newer version of the 30m digital elevation model, in which the original 20m contours were supplemented with, for example, more spot elevation data and a better coastline contour. Boundary errors were minimised by processing contiguous areas (such as the whole of the North Island) together, which wasn't possible when it was originally created.Major updates include the revision of catchment land use information, by overlaying with the land cover database (LCDB3, current as at 2008), and the update of river and rainfall statistics with data from 1960-2006.
The river network and associated attributes have been assembled within an ArcGIS geodatabase. Topological connectivity has been established to allow upstream and downstream tracing within the network. REC2 can be downloaded or streamed and used directly in ArcMap. (A file geodatabase version for ArcGIS of REC2 can be downloaded as a zip file and used directly for analyses in ArcMap from here)This is based on REC2 (Version 5) , June 2019 - a publicly available dataset from NIWA Taihoro Nukurangi.NIWA acknowledges funding from the MBIE SSIF towards the preparation of REC v2.5Coordinate Reference System: NZTM (New Zealand Transverse Mercator, EPSG: 2193)Geometric Representation of Rivers: LinesExtent (Bounding Box):

Top(Latitude) -33.9534Bottom(Latitude) -47.4867

Left (Longitude) 166.2634

Right (Longitude) 178.9733

_Item Page Created: 2022-01-19 03:43 Item Page Last Modified: 2025-04-05 18:03Owner: NIWA_OpenDataNZ Rivers and NamesNo data edit dates availableFields: CATAREA,CUM_AREA,nzsegment,LENGTHDOWN,Headwater,StreamOrde,upElev,downElev,headw_dist,segslpmean,LID,reachtype,FROM_NODE,TO_NODE,Shape_Leng,RivName

The River Environment Classification (REC) is a database of catchment spatial attributes, summarised for every segment in New Zealand's network of rivers. The attributes were compiled for the purposes of river classification. Examples where the REC can be used include, catchment rainfall calculations, catchment river flows, flood forecasting, land use and catchment associations.Creationthe REC was originally created using a hydrological networking tools and a digital elevation model.REC2 (River Environment Classification, v2.5) - June 2019 [Hosted Feature Layer]This service depicts rivers as lines and catchments as polygons The River Environment Classification (REC) is a database of catchment spatial attributes, summarised for every segment in New Zealand's network of rivers. The attributes were compiled for the purposes of river classification, while the river network description has been used to underpin models. Typically, models (e.g. CLUES and TopNet) would use the dendritic (branched) linkages of REC river segments to perform their calculations. Since its release and use over the last decade, some errors in the location and connectivity of these linkages have been identified. The current revision corrects those errors, and updates a number of spatial attributes with the latest data. REC2 provides a re-cut framework of rivers for modelling and classification. It is built on a newer version of the 30m digital elevation model, in which the original 20m contours were supplemented with, for example, more spot elevation data and a better coastline contour. Boundary errors were minimised by processing contiguous areas (such as the whole of the North Island) together, which wasn't possible when it was originally created.Major updates include the revision of catchment land use information, by overlaying with the land cover database (LCDB3, current as at 2008), and the update of river and rainfall statistics with data from 1960-2006.
The river network and associated attributes have been assembled within an ArcGIS geodatabase. Topological connectivity has been established to allow upstream and downstream tracing within the network. REC2 can be downloaded or streamed and used directly in ArcMap. (A file geodatabase version for ArcGIS of REC2 can be downloaded as a zip file and used directly for analyses in ArcMap from here)This layer is using Esri's ArcGIS Online Optimizations for fast rendering.This is REC2 (Version 5) , June 2019 - a publicly available dataset from NIWA Taihoro Nukurangi.NIWA acknowledges funding from the MBIE SSIF towards the preparation of REC v2.5Coordinate Reference System: NZTM (New Zealand Transverse Mercator, EPSG: 2193)Geometric Representation of Rivers: LinesExtent (Bounding Box):

Top(Latitude) -33.9534Bottom(Latitude) -47.4867

Left (Longitude) 166.2634

Right (Longitude) 178.9733

_Item Page Created: 2021-07-09 05:34 Item Page Last Modified: 2025-04-05 20:43Owner: NIWA_OpenDataNZ Rivers and NamesNo data edit dates availableFields: CATAREA,CUM_AREA,nzsegment,LENGTHDOWN,Headwater,StreamOrde,upElev,downElev,headw_dist,segslpmean,LID,reachtype,FROM_NODE,TO_NODE,Shape_Leng,RivName

This layer contains the DSM for LiDAR data in Gisborne and Hawke's Bay following Cyclone Gabrielle, captured from 26 February to 15 March 2023.

• The DEM is available as layer Gisborne and Hawke's Bay - Cyclone Gabrielle Post Flood LiDAR 1m DEM (2023)

• The Index Tiles are available as layer Gisborne and Hawke's Bay - Cyclone Gabrielle Post Flood LiDAR Index Tiles (2023)

LiDAR was captured for NIWA and the New Zealand Government by University of Canterbury and Christchurch Helicopters from 26 February to 15 March 2023. Coverage includes Aropaoanui River, Esk Valley, Heretaunga Plains (Ngaruroro and Tutaekuri Rivers), Mangahauini River (Tokomaru Bay), Tangoio (Te Ngarue Stream), Tukituki River, Uawa River (Tolaga Bay), Waipaoa River and Wairoa River. Data management and distribution is by Toitū Te Whenua Land Information New Zealand.

Data contacts: University of Canterbury - James Brassington and Justin Stout NIWA - Hamish Biggs, Emily Lane and Andrew Tait

Data comprises:

• DEM: tif or asc tiles in NZTM2000 projection, tiled into a 1:1,000 tile layout

• DSM: tif or asc tiles in NZTM2000 projection, tiled into a 1:1,000 tile layout

Vertical datum is NZVD2016.

Intended UseThe River Network is a geometric network and should be used for visualising the main rivers, streams and drains in Canterbury. It forms the basis for the Rivers for Allocation layer and Stream Depletion Calculations, which link to the Water Allocation Calculator— allocation summary reports to be used by the Customer Services, Planning, Consents, and Science teams. The River Network is based on LINZ river layer and aerial imagery. Attributes include Māori and English river names, river type, feature type, and source metadata. The River Network is hydrologically connected and traceable. Attributes still to be assigned to network include drain type, permanence, and bed extent. Attributes from NIWA’s River Environment Classification (REC) layer that make up the river type classification (network position, climate, source of flow, geology, landcover and valley landform) have been spatially associated but still need to be quality checked. DisclaimerThis information is accurate to the best of Environment Canterbury’s knowledge and belief. While Environment Canterbury has exercised reasonable skill and care in the preparation, recording and management of this information, this information may be subject to changes as more information becomes available. Environment Canterbury accepts no liability in contract, tort or otherwise for any direct, indirect, consequential or incidental damage, loss, injury or expense that arises from any errors in the information, whether due to Environment Canterbury or a third party, or that arises from the provision, use, or misuse, of the information available from this site. Attribute InformationRiver Information:RiverName – name of river, catchment, or surface water body as defined by LINZMāoriName – Māori name of river, catchment, or surface water body as defined by LINZDrainType – type of drain, as described in Hinds drains layer (i.e. Main, Secondary)Permanence – permanence of river flow (i.e. Perennial (P), Ephemeral (E), Intermittent (I)); null values for now, as these category definitions still need to be agreed upon across teamsBedExtent – width of the riverbed; will accompany braided river polygon layerRiverType – river classification based on REC characteristics and water quality scientist review; values have been spatially derived, but need to be reconfirmedFeatureType – type of line feature (i.e. river, drain, braided river centreline)Environmental Characteristics: see REC attributes metadataClimate – affects patterns of water quality, flood frequency, low flow period, evapotranspiration; climate categories (i.e. warm-dry WD, cool-extremely-wet CX)SourceOfFlow – topography influences sediment patterns, erosion, precipitation storage, and river form; flow categories assigned using a mix of topographic data (i.e. glacial-mountain GM, mountain M, hill H, low-elevation L, lake Lk) and manual designation (i.e. spring Sp, wetland W, regulated R)Geology – catchment geology controls groundwater storage capacity and transmissivity; developed from the toprock category in the Land Resources Inventory (LRI) (i.e. alluvium Al, hard sedimentary rocks HS, soft sedimentary SS, volcanic basic VB, volcanic acidic VA, plutonics Pl, miscellaneous M)Landcover – control for rainfall capture or runoff and potential evapotranspiration; categories developed from New Zealand Land Cover Database (LCDB) (i.e. bare ground B, indigenous forest IF, scrub / tussock T, pastoral P, exotic forestry EF, urban U)NetworkPosition – stream order relates to river form (i.e. low-order LO for headwater streams, middle-order MO for tributaries, high-order HO for main stems)ValleyLandform – indicative of geology and geomorphology, including erosive / depositional setting; derived from slope (i.e. high-gradient HG, medium-gradient MG, low-gradient LG) GIS Attributes:Spatial IDs: ObjectID, GlobalIDSpatial Fields: Shape, Shape.STLength()Source – data source (LINZ river lines, aerial imagery, ECan)SourceNote – note about data source (i.e. specific source layer)History Fields: CreatedBy, CreatedDate, ModifiedBy, ModifiedDate

This feature layer is designed for the purpose of assignment of waterway names (where named) to all segments within the River Environment Classification version two (REC2). This layer can also be joined to the main REC2 feature class layer via the unique joining variable called "nzsegment".The River Environment Classification (REC) is a database of catchment spatial attributes, summarised for every segment in New Zealand's network of rivers. The attributes were compiled for the purposes of river classification. Examples where the REC can be used include, catchment rainfall calculations, catchment river flows, flood forecasting, land use and catchment associations.Creationthe REC was originally created using a hydrological networking tools and a digital elevation model.In preparing The New Zealand Rivers and Names, all reasonable skill and care was exercised and the best available data and methods were used. Nevertheless, NIWA does not accept any liability, whether direct, indirect or consequential, arising out the use of this tool and its associated data and statistical information._Item Page Created: 2021-10-05 03:31 Item Page Last Modified: 2025-04-05 16:10Owner: NIWA_OpenData