Mangapōike River

{{Use New Zealand English|date=April 2024}}

{{Use dmy dates|date=July 2019}}{{Infobox river

| name = Mangapōike River

| image = Mangapōike River.png

| image_size =

| image_caption = Mangapōike River in 1911

| source1_location = Whakapunake

| mouth_location = Wairoa River

| subdivision_type1 = Country

| subdivision_name1 = New Zealand

| length_km = 42

| length_ref = {{LINZ|41824|Mangapōike River|2022-12-20}}

| source1_elevation = {{convert|962|m|abbr=on}}

| mouth_elevation = {{convert|20|m|abbr=on}}

| discharge1_avg =

| basin_size =

}}The Mangapōike River is a river beginning in the Gisborne Region of New Zealand's North Island. It flows generally southwest from sources south of Waingake, reaching the Wairoa River in Hawke's Bay {{convert|10|km|mi|0}} northeast of Frasertown. Mangapōike River was Gazetted as an official name on 28 November 2022.{{Cite web |date=28 November 2022 |title=Mangapōike River |url=https://gazetteer.linz.govt.nz/place/28173 |access-date=2023-11-05 |website=gazetteer.linz.govt.nz}}

Whakapunake at {{Convert|962|m|abbr=on}} is the highest point in the catchment, with the Mangarangiora Stream draining its eastern slopes into the Mangapōike.{{Cite web |title=Whakapunake, Hawke's Bay |url=https://www.topomap.co.nz/NZTopoMap/nz2350/Whakapunake/ |access-date=2023-11-05 |website=NZ Topo Map |language=en}} Whakapunake is traditionally where Māui snagged his fish hook. It is the northern boundary of Ngāti Kahungunu's rohe.{{Cite web |last=Whaanga |first=Mere |date=3 March 2017 |title=Ngāti Kahungunu - Tribes and lands |url=http://www.TeAra.govt.nz/en/ngati-kahungunu/page-1 |access-date=5 November 2023 |website=Te Ara - the Encyclopedia of New Zealand }} A {{Convert|200|ft|abbr=on}} transmitter mast was built at the south end of Whakapunake in 1969.{{Cite web |title=Come In Wntv-1 - Gisborne Photo News - No 178 : April 23, 1969 |url=https://photonews.org.nz/gisborne/issue/GPN178_19690423/t1-body-d7.html |access-date=2023-11-05 |website=photonews.org.nz |language=en}} It is now operated by Kordia.{{Cite web |last= |first= |title=Creating a Sustainable Business |url=https://www.kordia.co.nz/sustainable-business |access-date=2023-11-05 |website=www.kordia.co.nz |language=en}} In the river's main catchment, {{Convert|740|m|abbr=on}} Pūkaroronui is the highest point.{{Cite web |title=Pukaroronui, Gisborne |url=https://www.topomap.co.nz/NZTopoMap/nz2224/Pukaroronui/ |access-date=2023-11-05 |website=NZ Topo Map |language=en}}

The main geological influence on the river is that it drains from the Mangaone Anticline to the Wairoa Syncline. Below Tukemokihi the river runs through Cenozoic limestones.{{Cite web |title=Maps - QMAP Digital Download |url=https://shop.gns.cri.nz/maps/qmap-digital-download/ |access-date=2023-11-05 |website=shop.gns.cri.nz}} From Tukemokihi, upstream, the rocks are Miocene mudstones and sandstones.{{Cite web |date=January 2000 |title=Geology of the Raukumara Area, vol. 6. Institute of Geological & Nuclear Sciences 1:250 000 geological map |url=https://www.researchgate.net/publication/313488695_Geology_of_the_Raukumara_area_Institute_of_Geological_Nuclear_Sciences_1250_000_geological_map_6}}

Lake Te Horonui formed after 25 February 2018, when about {{Convert|200|m|abbr=on}} of a sandstone hill slipped and dammed the river. The landslide was probably due to the river cutting into the foot of the dip slope, where water trapped in the sandstone by an impermeable mudstone may have lubricated the bedding plane.{{cite journal |last1=McGovern |first1=Sam |last2=Brook |first2=Martin S. |last3=Cave |first3=Murry |title=Geomorphology and triggering mechanism of a river-damming block slide: February 2018 Mangapoike landslide, New Zealand |journal=Landslides |date=March 2021 |volume=18 |issue=3 |pages=1087–1095 |doi=10.1007/s10346-020-01572-7}} After over {{Convert|144|mm|abbr=on}} of rain fell on 9–10 March, the {{Convert|50|m|abbr=on}} deep lake grew from {{Convert|9|ha|abbr=on}} to {{Convert|30|ha|abbr=on}} and soon to {{Convert|33|ha|abbr=on}}. The bridge to Mangapōike Station might have flooded if a channel hadn't been blasted on 28 March and 9 April, allowing water into another new lake, Tukemokihi, and lowering Lake Te Horonui back to {{Convert|30|ha|abbr=on}}. Part of the detached slide block remained as a mass of around 8.5 million tonnes. The new lake is being used by grebes.{{Cite web |date=2020 |title=Our land, our soil |url=https://www.gdc.govt.nz/__data/assets/pdf_file/0026/9971/soe-report-2020-land-soil.pdf |website=Gisborne District Council}} The name Lake Mangapōike was also considered, but The Minister for Land Information, Damien O’Connor, agreed to the new name, which refers to the landslide.{{Cite web |last=Sharpe |first=Marty |date=2022-11-29 |title=Dispute over naming NZ's 'newest lake' goes all the way to the top |url=https://www.stuff.co.nz/national/130608497/dispute-over-naming-nzs-newest-lake-goes-all-the-way-to-the-top |access-date=2023-11-06 |website=Stuff |language=en}}

There are three gravel roads in the valley, but they have no direct link to each other. From the tar-sealed Tiniroto Road, Kotare Road runs a few kilometres east.{{Cite web |title=Mangapoike River, Hawke's Bay |url=https://www.topomap.co.nz/NZTopoMap/nz2201/Mangapoike-River/ |access-date=2023-11-05 |website=NZ Topo Map |language=en}} It ends at a gorge (named by one study as Haupatanga), which is over {{Convert|100|m|abbr=on}} deep and largely inaccessible.{{Cite thesis |title=Stratigraphy and sedimentology of Pliocene limestones, Wairoa district, northern Hawke's Bay |url=https://researchcommons.waikato.ac.nz/handle/10289/6067 |publisher=University of Waikato |date=2011 |degree= |language=en |first=Zichun (Jared) |last=Jiang}} Mangapōike Road runs through the Makaretu Stream valley to join the Mangapōike valley and then along the south bank of the river to Tukemokihi.{{Cite web |title=Mangapoike River, Hawke's Bay |url=https://www.topomap.co.nz/NZTopoMap/nz2210/Mangapoike-River/ |access-date=2023-11-05 |website=NZ Topo Map |language=en}} The upper catchment is partly accessed by Paparatu Road.{{Cite web |title=Mangapoike River, Gisborne |url=https://www.topomap.co.nz/NZTopoMap/nz2370/Mangapoike-River/ |access-date=2023-11-05 |website=NZ Topo Map |language=en}}

A preliminary survey for the Napier-Gisborne railway in 1905 favoured using the valley,{{Cite web |title=Public Works Statement. By the Hon. W. Hall-Jones, Minister for Public Works, 29th August, 1905 |url=https://atojs.natlib.govt.nz/cgi-bin/imageserver/imageserver.pl?oid=AJHR1905-I.1.3668&ext=png |access-date=2023-10-26 |website=atojs.natlib.govt.nz}} with a tunnel linking it to Te Ārai valley.{{Cite web |date=1905 |title=Public Works Map Showing the Railways of North Island |url=https://paperspast.natlib.govt.nz/parliamentary/appendix-to-the-journals-of-the-house-of-representatives/1905/I/3673?large_image=true |access-date=2023-10-26 |website=paperspast.natlib.govt.nz}} It was rejected in 1912, in favour of Hangaroa, Waikura and Ngātapa, as they served an area thought to have more economic potential.{{Cite web |date=9 February 1912 |title=Hawke's Bay-Gisborne Railway. Hawke's Bay Tribune |url=https://paperspast.natlib.govt.nz/newspapers/HBTRIB19120209.2.13 |access-date=2023-11-04 |website=paperspast.natlib.govt.nz}}

File:Mangapōike_River_map.jpg

There were two small schools in the valley. Paparatu School was on Paparatu Road. It was built in 1938,{{Cite web |date=20 June 1938 |title=School buildings. Poverty Bay Herald |url=https://paperspast.natlib.govt.nz/newspapers/PBH19380620.2.15 |access-date=2023-11-05 |website=paperspast.natlib.govt.nz}} had 14 on its roll in 1947{{Cite web |date=1949 |title=Progress of Education |url=https://nzetc.victoria.ac.nz/tm/scholarly/tei-MacHist-t1-body-d38-d8.html |access-date=2023-11-05 |website=nzetc.victoria.ac.nz}} and closed between 1978{{Cite web |date=1978 |title=1:63360 map Sheet: X18 Tiniroto |url=http://www.mapspast.org.nz/?zoom=13&x=2006300&y=5690128&layerid=NZMS1%201979 |access-date=2023-11-05 |website=www.mapspast.org.nz}} and 1986.{{Cite web |date=1986 |title=1:63360 map Sheet: X18 Tiniroto |url=http://www.mapspast.org.nz/?zoom=13&x=2006300&y=5690128&layerid=NZMS1/260%201989 |access-date=2023-11-05 |website=www.mapspast.org.nz}} Tukemokihi School was open by 1931.{{Cite web |date=18 December 1931 |title=School examinations. Poverty Bay Herald |url=https://paperspast.natlib.govt.nz/newspapers/PBH19311218.2.4 |access-date=2023-11-05 |website=paperspast.natlib.govt.nz}} It closed at the end of 2006{{Cite web |date=28 September 2006 |title=Tukemokihi School (2708) Closure Notice |url=https://gazette.govt.nz/notice/id/2006-go6639 |access-date=2023-11-05 |website=gazette.govt.nz}} and was given back to its previous landowners in 2012.{{Cite web |last=SHARPE |first=MARTY |date=2015-07-03 |title=Old school properties in a class of their own |url=https://www.stuff.co.nz/national/69787830/old-school-properties-in-a-class-of-their-own |access-date=2023-11-05 |website=Stuff |language=en}}

Paparatu was the scene of an ambush on Te Kooti in 1868, after his escape from Rēkohu.{{Cite web |date=1879 |title=Chapter XXXVII. — Te Kooti's Progress. — The Fight at Paparatu. The Colonial Troops Defeated with Loss of Two Killed, Ten Wounded, and £1200 Worth of Horses and Camp Equipage |url=https://nzetc.victoria.ac.nz/tm/scholarly/tei-GudRemi-t1-body1-d38.html |access-date=2023-11-05 |website=nzetc.victoria.ac.nz}}

Gisborne's water supply comes partly from reservoirs at the head of the valley. Water was first piped from the Mangapōike valley in 1917. In October 1942 ratepayers approved a £45,000 loan for a 246 million gallon {{Convert|246000000|impgal|m3|abbr=on}} reservoir, designed by G. F. Clapcott, the borough engineer, with a {{Convert|3.25|mi|abbr=on}} pipeline and an {{Convert|80|ft|abbr=on}} tunnel to Te Ārai valley.{{Cite web |date=1949 |title=Gisborne's Water Supply Problem |url=https://nzetc.victoria.ac.nz/tm/scholarly/tei-MacHist-t1-body-d39-d4-d3.html |access-date=2023-11-05 |website=nzetc.victoria.ac.nz}} The arch dam{{Cite web |date=6 February 1950 |title=Gisborne Herald |url=https://paperspast.natlib.govt.nz/newspapers/GISH19500206.2.24 |access-date=2023-11-05 |website=paperspast.natlib.govt.nz}} is {{Convert|50|ft|abbr=on}},{{Cite web |title=Water For Gisborne A Photo Survey Of The Scheme - Gisborne Photo News - No 105 : March 21, 1963 |url=https://photonews.org.nz/gisborne/issue/GPN105_19630321/t1-body-d10.html |access-date=2023-11-05 |website=photonews.org.nz |language=en}} or {{Convert|40|ft|abbr=on}} high, covers {{Convert|58|acre|abbr=on}} and filled in May 1948. A new pipeline and a {{Convert|330|ft|abbr=on}} tunnel{{Cite web |date=6 February 1950 |title=Mangapoike Dam & Water Storage Areas Inspected. Gisborne Herald |url=https://paperspast.natlib.govt.nz/newspapers/GISH19500206.2.25 |access-date=2023-11-05 |website=paperspast.natlib.govt.nz}} now connects the 1948 Clapcott Dam, the 1972 Sang Dam ({{Convert|347,568|m3|impgal|abbr=on}}) and the HC Williams Dam, built in 1974 ({{Convert|1,833,491|m3|impgal|abbr=on}}).{{Cite web |date=7 April 2020 |title=Drinking Water Supply Solid For The Region |url=https://community.scoop.co.nz/2020/04/drinking-water-supply-solid-for-the-region/ |access-date=2023-11-06 |website=Scoop |language=en}} In 2023 Cyclone Gabrielle damaged 9 of the 21water pipe bridges in the network and left two of reservoirs with cloudy water.{{Cite web |last= |first= |date=2023-05-08 |title=City water pipeline |url=https://www.gdc.govt.nz/services/tairawhiti-road-to-recovery/City-water-pipeline |access-date=2023-11-05 |website=Gisborne District Council |language=en}} Sang has an earth dam.{{Cite web |title=Sang Dam Assessments |url=https://lde.co.nz/project/sang-dam-assessments/ |access-date=2023-11-05 |website=LDE (Engineering Consultants) |language=en-NZ}}

The Cyclone also left forestry slash backed up for more than {{Convert|50|m|abbr=on}} at the bridge where the Mangapōike joins the Wairoa.{{Cite web |date=2023-02-18 |title=A view from above: surveying the cyclone damage in Tairāwhiti |url=https://www.rnz.co.nz/news/national/484452/a-view-from-above-surveying-the-cyclone-damage-in-tairawhiti |access-date=2023-11-05 |website=RNZ |language=en-nz}} Te Puna Bridge, near Tukemokihi,{{Cite web |date=11 May 2023 |title=Engineers' Stories – Kiriana Andrew |url=https://www.engineeringnz.org/news-insights/engineers-stories-kiriana-andrew/ |access-date=2023-11-05 |website=www.engineeringnz.org |language=en}} had a pier damaged.{{Cite web |title=Roading {{!}} Wairoa District Council |url=https://www.wairoadc.govt.nz/services/roading/ |access-date=2023-11-05 |website=www.wairoadc.govt.nz}}