Report to ENVIRONMENTAL PLANNING & REGULATIONS Committee for information

Transcription

1 Title: Section: Prepared by: State of Gravel Resource in the District Environmental Services & Protection Paul Murphy (Team Leader Water & Coastal Resources) Meeting Date: 7 February 2018 Legal Financial Significance = low Report to ENVIRONMENTAL PLANNING & REGULATIONS Committee for information SUMMARY The purpose of this report is to outline the state of the gravel resources in the Gisborne Region. This report will also go to the Assets & Infrastructure Committee meeting on 8 February 2018 for information. Gravel extraction is managed through policy and rules in the Gisborne Regional Freshwater Plan. A number of rivers in the Gisborne Region are aggrading. This is often due to the soft erodible sedimentary geology of sandstones and mudstones causing the river bed levels to rise. This can lead to increased bank erosion and the loss of productive land. The increasing demand of the gravel resource from forestry companies for forestry roading purposes has led to concerns about the potential effects on the riverine environment. Consequently, a series of technical reports analysing survey data of river bed levels was commissioned to improve our understanding of the bed load budget available for gravel extraction. This work has shown that bed aggradation levels in some rivers has slowed, and some locations are no longer aggrading, and down cutting is occurring. In some rivers the gravel resource may be fully allocated. The next step is to develop catchment based gravel extraction management plans with the priority placed on the Mata and Karakatuwhero catchments. The decisions or matters in this report are considered to be of low significance in accordance with the Council s Significance and Engagement Policy. RECOMMENDATIONS That the Environmental Planning & Regulations Committee: 1. Notes the contents of this report. Authorised by: Nicholas Zaman Director Environmental Services & Protection Keywords: gravel, gravel management, gravel extraction Page 1 of 5

2 BACKGROUND 1. Gravel extraction is managed through the Gisborne Regional Freshwater Plan (the Plan). 2. The Plan encourages gravel extraction to occur in areas where it provides the most benefit for river management purposes, minimising flood risk and maintaining or protecting existing structures. 3. Gravel extraction management is required to ensure: The potential effects on significant habitats and activities of native species are minimised; There is no alteration to rates of aggradation or bank erosion; There is no damage to sites of cultural significance; and There is no reduction in value for activities such as mahinga kai harvesting, recreational use, public access and impacts on natural character and amenity values. 4. Gravel extraction can only be undertaken in Outstanding Waterbodies if it is provided for in a Gravel Management Plan for that Outstanding Waterbody. The Outstanding Waterbodies in our region are: Te Arai River headwaters Urukokomuka Stream Lake Repongarae Motu River from and including the Motu Falls to the State Highway 35 Bridge including the Waitangirua, Mangaotane, Te Kahika and Mangatutara Streams Takaputahi River below its confluence with the Whitikau Stream The Ruakituri River from the headwaters to the Gisborne District Council boundary. 5. Gravel extraction demand is increasing as a result of increased forestry harvest and the use of gravel to construct forestry roads. As a result, concerns have been raised by community members and iwi as to how gravel extraction operations may be affecting the riverine environment. 6. The forestry industry has indicated peak harvest of the first rotation forests is not for several more years. Gravel extraction demand is likely to continue as road building is required. RIVER CROSS SECTION INFORMATION 7. Council staff survey a large number of river cross sections in the region on a regular basis. The cross sections were originally developed by the former Poverty Bay Catchment Board and the East Cape Catchment Board in the 1950 s and 1960 s. These cross sections were established primarily to monitor the rapidly aggrading river beds in the region. The cross section measurements have been recorded in a database allowing mean (average) bed levels to be calculated for each survey. 8. Monitoring occurs by a comparison of successive mean bed level calculations at specified cross sections over the river reach. Mean bed levels are calculated for the part of the river considered to be the active bed, which is the part of the bed that moves during a flood. 9. Mean bed level calculations are useful to assess the impact of gravel extraction when they are positioned upstream and downstream of the extraction site. Surveys should be undertaken prior to, and after, gravel extraction operations. However, the past surveys do not fulfil this criteria. Page 2 of 5

3 However, they do provide an assessment of the wider trends of bed level increasing or decreasing over time. 10. The Water and Coastal Resources Team commissioned a series of technical reports which analysed survey data of bed levels from 1956 to present. A total of 15 reports have been produced since July The reports have assessed general trends in bed level data in the following river catchments; Waiapu River Catchment River Bed Level Trend Implication Waiapu River Upper catchment gradually increasing; however, lower catchment no significant trend. Not a high priority for a gravel management plan. Good location to continue gravel extraction activities. Mata River Upper catchment decreasing, lower catchment increasing. Many of the gravel extraction sites are in the upper catchment over time these should be moved downstream to where the river is still aggrading. A gravel management plan is required. Makarika Stream Gradually increasing Unknown Makatote and Kopuaroa Stream Gradually decreasing Unknown Paoaruku Stream Gradually increasing Unknown Mangaoporo River Increasing Large gravel abstraction resource available. Tapuaeroa River Increasing Large gravel abstraction resource available. Waiorongomai stream Increasing, poor quality bed Despite large resource, unlikely to be suitable quality of Raparapaririki Stream Recently rate is decreasing. This is the source of some of the gravel resource heading down into the Tapuaeroa River. Poroporo River Increasing, recently rate has slowed. Despite large resource, unlikely to be suitable quality of Page 3 of 5

4 Maraehara River No significant trend Unknown Manutahi Stream Gradually decreasing trend Unknown Mangaharei Stream Gradually decreasing trend Unknown East Cape Rivers Karakatuwhero River Waipaoa River Catchment No significant trend, geology contributes less bed load Gravel resource may be fully allocated. A gravel management plan is required. Mangatu River Gradually increasing Not a high priority for a gravel management plan. Good location to continue gravel abstraction activities. 12. Trend reports on the following rivers are not complete: East Coast; Awatere, Taurangakautuku, Kopuaponamu, Oweka and Waikura Rivers. Hikuwai River catchment, Pauariki Stream Waipaoa River catchment, Waipaoa River. DISCUSSION 13. The bed level trend reports are the first indication that river bed aggradation is no longer continuing to occur in all rivers used for gravel extraction. The reason for aggradation slowing is the combination of afforestation stabilising the upper catchment areas (gravel sources) and the lack of significant flooding/destabilisation activity since the 1980s. 14. Despite the trends changing, in most locations there is still a very large area of gravel which has been built up over the decades for example the Mata River bedload; however, in the medium term some gravel extraction operations may need to move, and the Council may need to be more cautious in issuing new consents in locations with stable or decreasing bed levels. 15. Based on the work done to date, the two rivers where there seems to be a need for a more planned gravel extraction approach are the Mata (where a large amount of gravel is abstracted from an area now identified as down-cutting) and the Karakatuwhero (where bed levels are stable). 16. The Freshwater Plan provides for catchment based gravel extraction management plans which identify where gravel extraction is acceptable and where gravel extraction shall be avoided. The plans are proposed to be developed with involvement from local hapū. Priority for development for these plans should be placed on the Mata and Karakatuwhero Rivers. 17. Until such time as the gravel management plans are prepared the technical reports provide useful information to inform the assessment of resource consent applications. Page 4 of 5

5 ASSESSMENT OF SIGNIFICANCE Criteria This Report The Process Overall The effects on all or a large part of the Gisborne district Low Low The effects on individuals or specific communities Low Medium The level or history of public interest in the matter or issue Low Low Inconsistency with Council s current strategy and policy Low Low Impacts on Council s delivery of its Financial Strategy and Long Term Plan. Low Low 18. The decisions or matters in this report are considered to be of low significance in accordance with Council s Significance and Engagement Policy. 19. Aggrading rivers are the cause of bank erosion and the loss of productive land which affects the livelihoods of landowners in the Gisborne Region. Community meetings have historically raised aggrading rivers and gravel extraction as issues affecting the community. The effects are Region wide due to the large area of forestry land use but are often concentrated in key areas close to major forests. Council roading contractors have also recently been accessing the gravel resource for some local roading requirements. COMMUNITY ENGAGEMENT 20. A workshop was held with the forestry industry outlining the findings of the reports on bed level trends in East Coast Rivers. East Coast hapū groups have expressed concerns regarding the volume of extraction, the potential ecological impacts and secondary impacts of truck movements, noise and dust. CONSIDERATIONS Financial/Budget 21. The budgeted costs cover the technical reports completed and forthcoming. Provided they are undertaken primarily using in-house resources, catchment based gravel management plans for the Karakatuwhero and Mata Rivers will be able to be developed over the next 3 years. Legal 22. There are no legal implications arising from the recommendations in this report. POLICY AND PLANNING IMPLICATIONS 23. Gravel abstraction is managed under the Freshwater Plan which provides for the development of gravel management plans. Catchment based gravel management plans will add value to the existing policies and plans. RISKS 24. Potential adverse effects of gravel extraction on the community and public will be minimised by identifying the state of the gravel resource, consulting with local hapū to develop a gravel management plan which will improve identifying where gravel extraction is recommended to occur. 25. NEXT STEPS Date Action/Milestone Comments July 2018 Discuss the development of a catchment based gravel management for the Mata River with local hapū Page 5 of 5