River Catchment Flood Models Hazards

The models have been prepared by consultants on behalf of Council. A total of seven catchment flood models were prepared to inform the maps. Tonkin & Taylor updated five of the models in 2021 and Orphanage/Orchard again in 2023 and these were peer reviewed by consultants Stantec and WSP Opus. WSP Opus updated two of the models in 2020 which were peer reviewed by Stantec in 2021. The flood model maps are available online at www.nelson.govt.nz, along with an explanation of the terms and scenarios. River flooding layers show areas modelled as flooding in a 1% AEP present day flood event and in a 1% AEP flood event in the year 2130. The floodway shows the main channel that carries floodwater. While usually aligned with natural channels, floodways can include artificial watercourses. Blocking a floodway can change floodwater flows, damage riverbanks, and increase flood levels.