HYDRO/Flood_Statistics_Henderson_Collins

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Service Description: 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 available
Areakm2 catchment area draining to the downstream end of this reach (square kilometres)
q100_reach ratio of Q100 (1% aep flood) to mean annual flood
H&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 northing
Region Regional council or unitary authority territory
Operator 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 series
GEV_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 (%)

3. 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 estimate
QIA_10y 10-yr (10% aep) IA estimate
QIA_20y 20-yr (5% aep) IA estimate
QIA_50y 50-yr (2% aep) IA estimate
QIA_100y 100-yr (1% aep) IA estimate
QIA_1000y 1000-yr (0.1% aep) IA estimate

4. 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

Map Name: NZ Flood Statistics Henderson Collins V2 Layer

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Service Item Id: 803ba6fed05b402fbe1351360d54580f

Copyright Text: National Institute of Water and Atmosphere (NIWA)

Spatial Reference: 2193 (2193)

Single Fused Map Cache: false

Initial Extent:

Full Extent:

Units: esriMeters

Supported Image Format Types: PNG32,PNG24,PNG,JPG,DIB,TIFF,EMF,PS,PDF,GIF,SVG,SVGZ,BMP

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Supports Dynamic Layers: true

Resampling: false

MaxRecordCount: 2000

MaxImageHeight: 4096

MaxImageWidth: 4096

Supported Query Formats: JSON, geoJSON, PBF

Supports Query Data Elements: true

Min Scale: 0

Max Scale: 0

Supports Datum Transformation: true

Child Resources: Info Dynamic Layer

Supported Operations: Export Map Identify QueryLegends QueryDomains Find Return Updates

HYDRO/Flood_Statistics_Henderson_Collins_V2 (MapServer)