Natural hazards and climate change
The investment needed to ensure our communities can withstand the effects of climate change and natural hazards will be significant. The longer we put off action, the more costly it will be to address this challenge.
We need to work together in facing these challenges and guide where we focus our efforts and investment.
Infrastructure,such as roading, drinking water, stormwater and wastewater, is central to our community wellbeing. We need to plan for and invest in it wisely. Maintaining existing and building new infrastructure must respond to urban growth trends as well as climate change and other hazards.
The evidence: what do we already know?
Mean sea level rise
» Mean sea level rise projections for 100 years range between 0.55m-1.35m
» Increased risk of inundation from tsunami and storm events as a result of sea level rise
» Surface and stormwater drainage affected by increased sea level and higher water tables
» Restriction of Waipaoa River mouth possible due to sea level rise and coastal sediment processes
» The Waipaoa Flood Control Scheme upgrade will protect the Poverty Bay Flats from a 100-year storm event including climate change factors to 2090.
Rise in temperature
» An increase in the average number of days above 25 degrees from 24.2 now to about 34 days in 2040.
» Number of evenings less than 0°C decreases from 8.5 to between 3.6 and 4.6 in 2040
» Fire danger index predicted to increase – the number of days with ‘very high’ or ‘extreme’ warnings will increase.
» Annual rainfall expected to decrease 1% by 2040 and 3% by 2090
» Time spent in drought in the Gisborne Region is projected to increase by 5-10% by 2040 and 10% by 2090 for low elevations. Time spent in extreme drought in eastern New Zealand projected to double or triple by 2040
» Increase in storm frequency and intensity
» Flooding magnitudes expected to increase
» Tairāwhiti is a tectonically active region – we live 70–90kms from the edge of one of the earth’s plates.
» Two damaging earthquakes in recent years:
> 1966 (magnitude 6)
> 2007 (magnitude 6.8). Three buildings collapsed in Gisborne City; 23 more barricaded and closed. $50 million damage to commercial buildings; more than 6,000 insurance claims from homeowners
» Remnants of tropical cyclones and storms periodically cause or contribute to flooding, erosion, coastal erosion and land instability.
» In the last 100 years large floods on the Poverty Bay Flats in 2005 (Labour Weekend), 2002 (Muriwai), 1988 (Cyclone Bola), 1985 (Ngatapa), 1977, 1948 and 1906.
» The Uawa and Waipaoa catchments were significantly affected by flooding during the June 2018 (Queens Birthday) storms. Uawa was heavily impacted by forestry slash mobilized by flood waters
» We have 270 kilometres of coastline - sandy beaches, rocky mudstone shores and headlands.
» Our coastline is exposed to both distant and local Tsunami events. » Our region is close to the Hikurangi Subduction Margin. Tsunami generated here may arrive at our coastline in ten minutes to half an hour.
» Our region has experienced sixteen local Tsunami since 1832. The largest tsunami was 11 meters high.
» The East coast has young, easily erodible sedimentary rocks and coarser sandstones with slip prone soils.
» The region is being uplifted at the rate of 4mm a year - this is very fast and results in rapid erosion of river systems.
» Drinking water: 31,700 residents connected to city water supply. Augmented water supply to Te Karaka and Whatatutu.
»Inadequate drinking water supplies for most of region (resilience)
»Resilience issues in town supply. A break in the supply pipe in February 2019 left the city with only a 24 hour supply.
» Wastewater: Reticulated wastewater treatment for city and Te Karaka. Septage disposal sites are situated in Te Araroa, Tikitiki, Ruatoria and Te Puia. » Our road network is susceptible to surface flooding, landslides and weather degradation.
» In 2016 there were 40 road closures due to flooding and landslides.
» 630km (28%) of the local road network and 29km of our state highways were closed as a result of the 2018 Queen’s Birthday storms. $26 million in damage to road network.
» Council’s urban wastewater network consists of 223km of mains pipes, 2806 manholes, 40 pump stations and the treatment plant.
» Our wastewater network can’t cope with the volume of water going through it during heavy rain events. Council has needed to discharge wastewater into our city rivers on 14 occasions since 2014.
Challenges and opportunities
Challenges - if we do nothing
» There will be a greater risk of damage to public infrastructure and private property from long-term coastal erosion, inundation and sea level rise.
» Remaining ecosystems unable to adapt to climate change. Shift in species composition and possible loss of regional biodiversity.
» Increased erosion and landslides from more intense storm events.
» Longer dry spells will place pressure on water supply and increase the likelihood of wastewater blockages and related dry weather overflows.
» Some crops and farming activities may become unsustainable due to climate change.
» Insurance implications for at risk areas.
» Some Marae, waahi tapu and heritage sites may become more vulnerable to certain natural hazards.
» An ageing population means reduced transport and mobility to respond.
» Diversify horticultural and perennial cropping within the region.
» Start the conversation with our community around how we respond to climate change
> Mitigation: reducing greenhouse gases
> Adaptation: managed retreat, infrastructure upgrades
» Strategic planning around the maintenance, delivery and location of resilient infrastructure
» Future irrigation demand planning
» Urban water tanks
» Low impact urban design
» Identify areas for development that are less vulnerable to the effects of climate change and natural hazards
» Development of a biodiversity restoration and ecosystem resilience programme
» Collaboration with neighbouring regions
» What is an acceptable level of risk for our communities?
» How do we get to this acceptable level of risk?
» Our coastal communities are more vulnerable to sea level rise and coastal inundation. Should we:
> build more protection measures?
> let these areas run down and slowly be destroyed?
> managed retreat?
> something else?
» How do we make our urban and rural communities more resilient to climate change?
» What work do we need to prioritise to offset the effects of climate change?
» What should our region do to mitigate the effects of climate change?
» How do we secure reliability and quality of water supply for all of our communities?
» How do we secure reliability and resilience in our energy supply network?