Waikato Region Modelled Local Flood Hazard Classification

Purpose: This data has been published to support the Waikato Regional Hazards Portal. Statement: River flood hazard classification for a 1% annual exceedance probability (AEP) event, derived from the (2D) modelled flood depth and flood speed data for a number of rivers and streams. To determine the potential flood hazard classification a matrix was designed combining both flood depth and flood speed. The hazard classification has been divided into three levels of river flood hazard based on the likely impact on people, property and surrounding environment. These are: 1. Low- The combined depth and speed of floodwaters are unlikely to impair the maneuverability or stability of the average person and damage to property is likely to be non- structural and mainly due to inundation and deposition of sediment. 2. Medium- The combined depth and speed of floodwaters are likely to start to impede the maneuverability or stability of the average person and damage to property is unlikely to be structural provided that weak points such as windows and doors are retained above flood level. 3. High- The combined depth and speed of floodwaters are likely to significantly impede the maneuverability or stability of the average person and damage to property is likely to be widespread and structural, including instances where building have been raised above the flood level. In addition, there is also Defended which covers areas defended from river flood hazards (by stopbanks or other protection measures). Data is presented as polygons showing potential flood hazard. Attribute information includes the year the modelling was completed (from 2006 onwards). Models have incorporated the best available information at the time of their creation, generally including (but not always) LiDAR data, and flood event survey assessments. A climate change component is generally included in the modelling and will likely be based on the best available MfE guidance from the period of modelling. Note that for Grahams Creek a climate change component is not included for the flood hazard classification, due to the design of the flood scheme to current climate only as a result of community consultation. The LiDAR data is converted to a grid which has limitation when assessing small stream channels and topographic features such as ridges. This may lead to minor discrepancies in water flows which may lead to limitations in defining flood extents. Internal drainage such as storm water systems, culverts, piping etc, are generally not included in the modelling. Depending on how the model is configured, they often only consider the main watercourse, so flooding of minor channels, tributaries, ponding and coastal inundation may not be represented by the flood extent. This information is not intended to replace more detailed hydrogeological and survey data required for Building Consents or Resource Consents. The information shown is current as of the time of modelling, including assumptions around climate change and hydrology etc. Note that this is a “live” dataset and further additions will be made as and when available and verified. WRC Natural Hazard Information Hierarchy: 1. Property to local scale Information that is suitable to be used for property specific purposes, including within District Plans, or for: • risk assessments • resource or building consents • decisions that concern personal or public safety • the conduct of commercial business • insurance purposes • land information memorandum reports (LIMs) The information is based on detailed hazard modelling or hazards mapping that includes both current and future possible scenarios, along with the associated likelihoods and impacts. Users should make sure they are using the most appropriate natural hazards data available. Data held by other organisations may be better suited for property scale use or may be more up to date. Before using any of the Waikato Regional Council natural hazard data at property scale or for subdivision development purposes please contact the Waikato Regional Council Regional Resilience team for guidance. Further information on resource consenting is available here. WRC Metadata: HAZARD.sdeadmin.HAZ_MOD_LOCAL_FLOOD_HAZ_CLASS - HAZARDS - Regional Hazards Portal - GIS Layers Terms of Use: This work is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License. Should users wish to distribute or publish derivatives or modified versions of this data then they must seek a data use agreement through WRC first. See the Waikato Regional Hazards Portal Terms of use here Waikato Regional Hazards Portal - Terms of use | Waikato Regional Council.