3.0 LAND USE AND PHYSIOGRAPHY
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Key points
- Total land area is 412 750 ha, of which 64% is in freehold title, 27% is in the conservation estate and 9% in other Crown land.
- Most of the utilised land is on erodible Tertiary sedimentary rocks, and 82% of the District is moderately steep to steep. As a result, shallow landsliding on pastoral land is extensive.
- Climatic conditions are variable, mildest near the coast and colder and wetter further inland. Summer drought is common.
3.1 Location
The Wairoa District covers 412 750 ha of northern Hawke's Bay. The
District is bounded to the north by steep hill country roughly forming the divide between
the Waipaoa catchment, which flows into Poverty Bay, and the Nuhaka and Wairoa catchments,
which flow through the District to the coast. In the west the District boundary is the
main divide between Hawke's Bay and the Bay of Plenty. In the south-west the boundary
follows the Waikare River from the coast inland and crosses the mid-section of the Mohaka
catchment to the main divide.
The information and data contained in this chapter are taken from the
Land Use Capability Classification of the Northern Hawke's Bay Region (Page 1988) and
Land Regions of Hawke's Bay (Eyles et al. 1993) or is derived from the Land Resources Inventory
database maintained by Landcare Research. The Wairoa District Council has provided summary
tenure data.
3.2 Rural land tenure
Wairoa District has over 400 individual rural freehold titles. In
addition to these there are substantial Crown lands which include reserve lands managed by
the Department of Conservation and land licensed to State-owned enterprises and other
commercial occupiers e.g. forest licenses, Landcorp farm properties, railway land. There
are also large areas in multiple ownership, much of which is managed by Trusts and/or
Incorporations on behalf of Maori owners. The ownership types are summarised by area in
Table 3.1.
Table 3.1 Summary of rural land tenure in Wairoa District by type
and area
Tenure type Area (ha) Crown - managed by DOC Crown - forest licences
Crown - other (SOE etc.)
Multiple ownership and freehold
110 189 20 924
17 282
264 355
Total 412 750
3.3 Physiography
The physiography of the District is controlled by rock type and geological structure.
The rock base is of greywacke and Tertiary sedimentary rocks. The greywacke is
concentrated in the Urewera ranges in the west of the District, and the sedimentary rocks
get younger and softer from the west to the coastal mudstone in the east. Where slopes are
less steep they remain overlain with rhyolitic volcanic tephra from the Taupo and Okataina
volcanic centres. On steep slopes in the centre and east of the District, most or all of
the airfall tephra has been removed through erosion. The soils that remain have
developed from the sedimentary rocks, and are highly susceptible to mass movement erosion.
The rate of mass movement erosion has increased since the removal of indigenous forest and
the development of pasture cover.
There are small but significant areas of accumulating materials, including the wide
alluvium plain at Wairoa, the narrow river terraces and the alluvial and sand plains and
dunes of the coastal strip.
The area is part of the larger 'East Coast deformed belt', and is tectonically active.
Numerous faults are present, although few have shown activity in historic time. Major
faults at Mohaka and Waikaremoana defined valley and basin systems in the past.
Earthquakes are common in the District, which lies within earthquake risk zone 1 of Clark et
al. (1965). The area is also subject to continued geological tilting and uplift, with
subsequent down-cutting by rivers and streams. The topography of the District is
influenced by the Wairoa syncline. Marked folding has produced long, gentle slopes facing
south-east, with steep northwest-facing slopes in the eastern part of the District.
3.4 Climate
The District is sheltered from New Zealand's prevailing westerly weather by the axial
ranges and is therefore generally sunnier, drier and less windy than the west coast.
Periodic cyclonic storms from the north or north-east occur, however, and prolonged
periods of drought (up to 5 months) are also common. The climate is therefore most noted
for its variability.
Conditions are mildest near the coast and become more extreme inland with increasing
altitude. Coastal areas are classified C1 by the NZ Meteorological Service, and are
characterised by warm summer day temperatures, which rise above 300C occasionally, dry foehn north-westerly winds, moderate
winter temperatures, maximum rainfall in winter and a marked decrease in the amount and
reliability of rainfall in spring and summer. Annual rainfall ranges from 1000 mm to 1500
mm.
The inland hill country is classified C3, and is cooler and wetter than
the coastal area. Annual rainfall ranges between 1500 mm and 2500 mm, with very heavy rain
at times from the south and south-east. Further inland the mountain areas have even higher
rainfall, with conditions varying widely with altitude and exposure.
There is one operational climatological station (Whakapunake) in the
Wairoa District; four others operated in the past are now closed.
3.5 Soils
Steepland phases of soils in the Wairoa district are formed from
Mesozoic greywacke and tertiary sediments and are erosion prone. The thin organic topsoils
have low shear strength, low cohesion and low water-holding capacity, leading to high
drought susceptibility. Tephra or sedimentary rocks form the parent material of most soils
in the District. There are five major soil groups (NZ genetic soil classification, Taylor
& Pohlen 1968) in the District.
- Yellow-brown pumice and related steepland soils - These soils are developed on Kaharoa Ash, Taupo Pumice and Waimihia Formation rhyolitic tephras where the tephra is of sufficient depth to be the primary parent material (generally exceeding 50 cm).
- Podsolised yellow-brown pumice and related steepland soils - These soils are developed from thicker deposits of the same tephras as the previous soils but under a higher rainfall regime leading to leaching of nutrients and iron banding in the subsoil. They are common in the mountains west of the District where rainfall exceeds 1500 mm/annum and at altitudes over 500 m a.s.l.
- Yellow-brown earths and related steepland soils - These soils are common in the drier, steep coastal hill country. They are developed on sedimentary rocks where annual rainfall is in excess of 1200 mm.
- Composite yellow-brown pumice soils on yellow-brown loams - These soils formed where Taupo Pumice and Waimihia Formation is less than 50 cm in depth and overlies older, more weathered tephras. The upper part of the profile has yellow-brown pumice characteristics over a subsoil of more weathered tephra. Areas of these soils occur on the Mahia Peninsula.
- Recent and gleyed recent soils - These soils are developed on alluvium in the river terraces and basins. They form a very small proportion of soils in the District.
3.6 Slope
An analysis of the predominant slope groups in the District is given in Table 3.2 and
contrasted with data for the North Island. The District has substantially more moderately
steep to very steep land (slope groups E-G) and less flat to strongly rolling land (slope
groups A-D) than the North Island generally .
Table 3.2 Areas of dominant slope groups recorded for Wairoa District in the NZLRI
| Dominant slope group | Area (ha) | % of District | % of North Island |
| A (0-30)
B (4-70) C (8-150) D (16-200) E (21-250) F (26-350) G (>350) Unmapped (rivers, towns, etc.) |
25 136 5 830 5 769 37 481 155 293 129 442 46 307 7 493 |
6.1 1.4 1.4 9.1 37.6 31.4 11.2 1.8 |
14.8 6.4 8.9 12.8 24.5 22.8 7.6 2.2 |
| Total | 412 750 | 100 | 100 |
3.7 Erosion
The steep river valley systems that have developed in the District on relatively recent
sedimentary rocks indicates that erosion has been an active, naturally occurring process
over recent geological time. The removal of the indigenous vegetation cover and
replacement by short grasses and grazing animals has accelerated the rate of erosion. This
has been recorded by farmers and scientists alike since the late nineteenth century.
The causes of erosion and the reasons for the District's susceptibility
to erosion are complex and include the underlying geological structure, modifications to
that structure by folding and faulting, rock type, earthquakes, soil properties, slope
characteristics (aspect, angle, shape), climate (rainfall intensity and duration),
vegetation management and other land-use practices.
The history of research and of soil conservation in the District is
short. The Hawke's
Bay Catchment Board operated two wind erosion control schemes at Mohaka and Mahia and a
catchment control scheme at Nuhaka in the 1960s, and have had soil conservation officers
based in Wairoa since 1962. The advisers provide technical and financial support to land
managers for soil protection works. Little earlier information exists. The relationship
between pasture productivity and shallow landsliding in the District was the subject of
research in the 1980s (Douglas et al. 1986).
The frequency of erosion types within the District, as mapped in 1978
and recorded in the NZLRI, is summarised in Table 3.3.
Table 3.3 Types and frequency of erosion occurring in the Wairoa
District (dominant type only)
| Dominant Erosion type | Inventory code | Area of map units affected (ha) | % of District |
| Soil slip Sheet Debris avalanche Gully Wind Earth flow Scree Slump Tunnel gully No erosion recorded Unmapped |
sS1 Sh daF G W eF Sc Su T |
223 596 7 296 76 746 2 600 3 230 5 370 249 2 418 122 83 630 7 493 |
54.2 1.8 18.6 0.6 0.8 1.3 <0.1 0.6 <0.1 20.3 2.2 |
| Total | 412 750 | 100 |
Soil slip and debris avalanche erosion are the most common. Deep earthflow erosion is
less common than in Gisborne or southern Hawke's Bay. Wind
erosion is significant locally along the coastal strip. Eighty percent of land in the
District is affected by some form of erosion.
3.8 Vegetation
District vegetation cover was mapped in the mid 1970s as part of the
NZLRI (Map 1). This data is now considerably out of date, but is still useful as a base
from which to test the validity of other data sets, e.g. area in indigenous forest
vis-a-vis the area managed by DOC. Similarly, current grassed area estimates plus exotic
plantations give a total close to the sum of the pasture, grassland, scrub and exotic
forest classes of 20 years ago.
Improved pasture in the District is dominated by ryegrass and white
clover but includes cocksfoot, timothy and subterranean clover. Pastures revert to brown
top, danthonia, sweet vernal, ratstail and flat weeds. Major weeds include the thistles
and barley grass. Ragwort is a problem in some areas. Maize as a cash crop is grown on the
river flats around Nuhaka, Opoutama and Wairoa. Viticulture is also developing in the
District, with a significant investment on the Mohaka terraces.
Indigenous coastal species are dominated by tauhinu, but manuka is the most widespread native regeneration species (scrub) in the District. The decline in profitability in pastoral farming over the past 10 years has seen significant areas of steeper grazed land reverting to manuka as fertiliser application rates and stocking rates decline. In wetter areas ring and bracken fern occur in association with manuka or form a substantial stand on their own. Scattered gorse infestations also occur in the District, particularly in the drier coastal areas. Blackberry is also a significant weed in much of the District.
Table 3.4 NZLRI vegetation class distribution for Wairoa District
| Vegetation group | NZLRI area (ha) | Proportion of total area (%) |
| Pasture/grassland Grassland/scrub Scrub/forest Exotic forest Indigenous forest Wetlands Dunelands Unmapped |
199 754 26 280 46 055 7 113 122 734 132 3 185 7 493 |
48.4 6.4 11.2 1.7 29.7 <0.1 0.8 2.2 |
| Total | 412 750 | 100 |
Indigenous forest in the District can be simply categorised into two classes (a)
podocarp hardwood and (b) beech forest. Only small remnant stands of lowland podocarp
hardwood forest (rimu dominant) remain in reserves and on private property. Some lowland
and mid altitude podocarp hardwood stands (Hall's totara, mountain toatoa)
remain in the mountain reserves in the west of the District. Most of the higher-altitude
forest is beech forest occurring as an association of a number of beech species. Red beech
and hard beech dominate below 1000 m a.s.l., mountain beech and silver beech above that
altitude.
The major exotic tree species is radiata pine. Hardwoods are of very
limited extent, although some other conifers are present, e.g. Corsican pine. Considerable
effort has gone into promoting conservation trees in the District, but because these are
generally established as scattered or watercourse plantings it is difficult to quantify
their extent.
Swamp and sand dune associations occur along the coastline east of
Wairoa.
3.8 Land Use Capability Classes and Suites
The NZLRI groups land in the District into a ranked scale of eight land
use capability (LUC) classes. These give an assessment of the capacity for sustained
productive use, taking into account physical limitations, management requirements and soil
conservation needs. Classes I-IV are suited to cultivation for arable use, or for pastoral
or forestry use. Classes V-VII are not suitable for arable use and of increasing
limitation to long-term pastoral use. Class VIII is reserved for land which is physically
unsuited to productive use and is best managed for protection and some recreation uses.
Seven classes are recorded in the District and the area of each class is
given in Table 3.5. The most versatile and potentially productive classes (I, II and III)
comprise less than 5.7% of the District, while land classified VI and VII account for 78%
and class VIII 12%. The distribution of thse classes is illustrated in Map 2.
(click thumbnail for full map)
Table 3.5 NZLRI land use capability class distribution in the Wairoa
District
| Land use capability class by area (ha) | ||||||||
I |
II |
III |
IV |
VI |
VII |
VIII |
Lakes/rivers/towns |
TOTAL |
895 |
3101 |
19 739 |
8605 |
194 741 |
127 970 |
50 206 |
7493 |
412 750 |
The specific limitations of class VI and VII are critical to the future of productive
land use and to understanding the impact of any change from pastoral farming to production
forestry. Although dependent on a range of factors, slope is the critical terrain
determinant in the move from one LUC class to another in the District. Class VI sites are
rarely over 251 in average slope and Class VII sites are rarely under 201 in slope, although this does
occur, for example, in wind-blown dunes and deep earthflow terrain.
To enable direct relationships between LUC units in the landscape to be
identified, related LUC units are aggregated into suites based on rock type, within which
units share physical characteristics that unite them in the landscape. Sixteen of these
have been identified for northern Hawke's Bay, of which 10 occur in the District (Map 3). A brief description of each
suite, the land use capability units included in it, its locality and limitations follows.
Table 3.6 NZLRI land use capability suite distribution in the Wairoa
District
| Land use capability suite | Area (ha) |
| 1. Alluvial plains and terraces 2. Sand dunes 3. Low angle unstable mudstone terrain 4. Jointed mudstone hill country 5. Banded mudstone hill country 6. Siltstone hill country 7. Sandstone hill country 8. Landforms with a mantle of Taupo airfall tephra 9. Raised marine terraces 10. Greywacke mountain and hill country with a mantle of Taupo airfall tephra Gorges and cliffs Lakes Rivers Towns |
14 760 3450 10 528 1963 40 169 50 381 35 296 193 448 1176 48 370 5716 6177 1018 298 |
| Total | 412 750 |
1. Alluvial plains and terraces
These are mainly located around Wairoa, but also as narrow inland river valleys and
elevated terraces at Mohaka. They contain the most versatile and productive soils in the
District, although they can be limited by poor drainage. They are less drought susceptible
than hill soils owing to the greater soil depth and finer soil texture and therefore
increased soil moisture-holding capacity. Sites in this suite pose little erosion hazard
apart from stream bank erosion of terrace edges, which can be locally severe, and some
risk of wind erosion if the lighter soil types are cultivated. There is limited access to
water on the upper terraces while underground or surface waterways can usually be tapped
from lower terraces
.
(click thumbnail for full map)
Targeted commercial forest development on these sites is precluded by the current
District plan. In a number of cases, properties purchased for forestry which have areas of
this type have been subdivided and the flats sold as lifestyle blocks. This can lead
either to intensification of land use and production (horticulture, deer) on these areas
or to reduced output (extensive grazing, hobby farming).
2. Sand dunes
A complex of sand dunes and plains occurs along the coast between Wairoa and Opoutama,
reaching 1 km inland at Nuhaka. Land use capability is dependent on the degree of exposure
to salt-laden winds, the degree of soil development and the risk of wind erosion. Most of
this suite is undeveloped, although versatility of use increases with increasing
stability, age and protection from wind. The soils are yellow-brown sands and have a high
potential for wind erosion, but current erosion is low because of a well established
vegetation cover. Water availability is poor and limited to interdune ponding. Dunelands
often contain sites of significant cultural value. Forest development has occurred on
similar sites elsewhere in the country, but growth rate and form are generally lower than
on more sheltered, fertile sites and so targeted development of commercial forests is not
expected in Wairoa District. Woodlot farm forestry is a suitable land use.
3. Low-angle unstable mudstone terrain
There are isolated pockets of deep-seated earthflow and slump erosion scattered
throughout the District, e.g. Mangaone Road. These areas are usually strongly rolling to
moderately steep and occur on crush zones or faults in jointed or bentonitic mudstone.
Mass movement erosion is the main limitation to use. Potential and severity of current
erosion is determined by the rock type, the removal of sediment from the toe of the slope
and the formation of gullies, which contribute to sediment removal. Although not large in
extent, they contribute substantially to local instability.
Most of this area is in high-producing pasture because of its easy contour and high
fertility, although rushes and sedges may be common because of poor drainage, which also
makes management difficult. Active erosion is difficult to control because it is deep
seated. Dewatering and stabilisation of gullies and the flow toe are critical. Block
establishment of tree species, gully and stream bank planting, spring tapping, diversion
of watercourses, surface smoothing and reshaping and exclusion of stock in winter all may
form part of a control strategy. Coordinated woodlot or commercial forest plantings will
assist in controlling active erosion on these sites.
4. Jointed mudstone hill country
There is only a small area of this terrain in the District, located near Morere. It is
characterised by hills with numerous narrow spurs and ridges, steep slopes and broken and
irregular surfaces formed by soil slip, earthflows and gullies. The land is primarily in
pasture, and is very susceptible to moderate and severe erosion depending on slope angle.
Soil slip erosion, shallow earthflows (<1 m deep) and narrow gullies characterise this
suite. Earth flows move slowly and intermittently and may not reach major watercourses. A
measure of erosion control can be achieved by space planting of erosion control trees,
gully plantings, use of debris dams to reduce gully erosion and careful control of winter
grazing.
5. Banded mudstone hill country
This suite is large and scattered throughout the District. It occurs particularly in
the Ruakituri, Mangaruhe and Mangapoike valleys and on Mahia Peninsula. It is
characterised by steep hills, gorges and bluffs with bedding of coarse hard sandstone
between layers of jointed or massive mudstone. Slopes are very long and planar and lead
straight into watercourses. In the Mangapoike bedding dips significantly and forms a
series of scarp and dip slopes which are a part of the Wairoa syncline. The land is
generally in pasture, often in association with manuka reversion (tauhinu reversion on
Mahia Peninsula) and gorse. Summer low flows from this terrain type are low (0.8-3
litres/sec/km2).
Erosion severity is closely related to slope steepness. Where bedding is well
developed, slopes are relatively stable. Slips on moderately steep slopes tend to have
their shear plane in the regolith and so can be recovered to pastoral farming with space
planting, fertiliser and careful management. On steep slopes, however, shallow soils slip
to bedrock and then fail to revegetate. The bare surface tends to erode back into the
bedrock. The bare area increases in size, with minor collapses and sheet wash. On very
steep slopes and in gorges the end result is large bare faces on which it is impossible to
reestablish vegetation cover. For this reason slipped areas on such slopes should be
retired or planted in trees. Control of scrub removal on such slopes is also recommended.
6. Siltstone hill country
This suite, centred on Wairoa, forms most of the coastal hill country between the
Waikare river and Nuhaka and extends inland between 5 and 20 km. The suite consists of
moderately steep to steep hill country managed for pastoral production and subject to
variable rainfall, i.e. both drought and very intensive rainfall. Easier slopes on similar
rock type but with significant ash cover and lower erosion risk are mapped separately as
suite 8. Erosion risk is high, with slip-inducing storms sufficient to disrupt farm
management occurring approximately every 3-5 years.
The siltstone rock types are young (Tertiary, Quaternary), with the youngest and
softest material near the coast. The considerable geological uplift in the District since
the middle Pleistocene has led to downcutting of streams and relatively high erosion
rates. Hill slopes in this suite have two major forms. Inland (Cricklewood Rd, Titirangi
Rd) slopes are long and planar, leading directly into streams. The coastal hills and those
east of the Wairoa River valley have a concave profile, producing terraces and colluvial
footslopes. There is a distinct change in soil depth, erosion and productivity between the
steep upper slope and the gentler footslope.
The incidence of slip erosion accompanied by sheet erosion is widespread on sites in
this suite, and is the highest in the region. Slipping is generally triggered by rainfall
events or occasionally by earthquakes. The majority of slips occur on steep upper slopes
and, depending on slope profile, deposit sediment in the watercourse or on the colluvial
footslopes as long debris flow tails. In the latter case regrassing on the colluvium is
complete in 2-3 years, but it takes 15-20 years to recover pasture productivity to a
stable but lower level on the slip scars. On shallow soils slipping can be to bedrock, but
the softer, weathered nature of the underlying rock means that the shear plane often
remains within the regolith. Slip erosion has a financial impact on farm management
through fence, track and bridge damage. Weed and scrub reversion is a problem,
particularly on shallow eroded soils and northern faces.
Summer low flow rates are low (0-3 litres/sec/km2) and runoff rates are
high, leading to significant stream bank erosion in storm events. Drought is a major
threat to marginal farming operations. Much of the original soil has now been stripped
from the upper slopes, and pasture productivity is significantly less than that on easier
land or the colluvial footslopes. Reduction in moisture holding capacity and fertility due
to soil loss are the major reasons for this. Appropriate retirement, block planting,
intensification of fertiliser and subdivision and erosion control plantings are all
advocated for this suite, but implementation is scarce.
Much of the recent forestry conversion has taken place on land in this suite and will
make a significant contribution to slope stability. The steep narrow ridges will require
cable harvesting and careful road construction to minimise further slip erosion.
7. Sandstone hill country
This suite is concentrated in the north (Nuhaka/Wharerata) and west of the District
(Mangapoike/Whakapunake), and is characterised by lower natural fertility than the
mudstone and siltstone hill country, leading to a higher percentage of scrub reversion and
a slower rate of recovery after erosion events. In coastal areas of lower rainfall in the
north drought is common, and in upland exposed areas frost, occasional snowfalls and
strong winds occur. Summer low flow rates are low (0-3 litres/sec/km2).
The sandstones vary in hardness and structure, from massive to bedded, with the
Whakapunake sandstone including limestone as well as mudstone beds. The dip of these beds
varies but uplifting and tilting has led to the formation of dip/scarp or cuesta
topography. Dip slopes are parallel to the bedding plane, and because they are less steep
in slope they retain a mantle of tephra, and are mapped in the next land use capability
suite.
Erosion is less severe in this suite than in the mudstone and siltstone suites but the
slower recovery rates mean that it remains a significant land management issue. The low
productivity and lower rates of erosion mean that this land is rarely targeted for erosion
control measures.
Pastoral farming is marginal on this country owing to the infertile parent material,
steep slopes and cool (exposed) wet climate. Reversion is a major land management problem,
the NZLRI mapping 38% in scrub and 54% in pasture with significant fern or scrub
components. Radiata pine growth potentials are high, and the rapid development in the
Nuhaka/Wharerata area is substantially in this suite.
8. Hill country landforms with a mantle of Taupo airfall tephra
This suite is mapped where the depth of the remaining tephra mantle is sufficient to
partially mask the properties of the underlying rock type. Its distribution is extensive
in the District, and reaches the coast at Nuhaka and in the south at Mohaka.
Before the widespread use of fertilisers and recognition of trace element deficiencies,
low-fertility soils and vigorous scrub reversion meant that farming of the land in this
suite met with limited success, and much of the land was not utilised until the 1940s. As
a result much of this land was developed by the State into farm settlement blocks or State
Exotic Forest (Patunamu, Mohaka, Wharerata). This suite was also targeted by private
commercial forest growers (Willow Flat, Maungataniwha). Large upland areas of this suite
remain in indigenous forest within the Urewera National Park. Terraces in this suite at
Mohaka Waikari and Waihua are being used for the production of cash crops.
The presence of a tephra mantle on a landscape indicates general stability and
relatively low erosion rates in the past. On steep sites, however, modification of
vegetation cover leads to soil slip and tunnel gully erosion, and on steep forested slopes
debris avalanches are characteristic. Wind erosion of these light friable soils is also
possible when they are cultivated. Summer low flow water yields are proportional to the
depth of tephra, and range from 2 to 5 litres/sec/km2.
Pastoral farming on this terrain requires high levels of fertiliser and management
inputs to maintain pasture and animal productivity. This has resulted in other land uses,
particularly commercial forestry, having a competitive advantage on these sites.
9. Raised marine terraces
This suite is mapped on Mahia Peninsula and Portland Island on flat to rolling raised
marine terraces. The sedimentary base rocks are overlain by a shallow mantle of coarse
Waimihia lapilli on top of more weathered tephra. Erosion and climate are regarded as the
major limitations to use, and in both cases wind is the main factor. The cropping
potential of sites in this suite is limited by wind erosion and the effect of salt-laden
winds on plant growth. There is considerable potential for intensive use in sheltered
areas, as the terraces have soils of medium to high fertility and adequate drainage and
the climate is mild. Land use is at present restricted to pastoral farming, mainly because
of distance to main centres. Production forestry development within this suite is
unlikely, although managed timber belts may be appropriate.
10. Greywacke mountain and hill country with a mantle of Taupo airfall tephra
This suite is extensive but confined to the south-west of the District in the proximity of the axial ranges and foothills. The vegetation is largely indigenous forest, although there are areas of exotic forest, scrub and grazed land on the less steep, lower-altitude hills on the margins of the ranges. The terrain is mountainous, closely dissected with steep to very steep slopes. Erosion is of moderate to slight severity because of the indigenous forest cover, but can be severe if forest cover is removed or after the occasional high-intensity cyclonic storm. Wind, sheet, slip and scree erosion can then be significant. The landforms in this suite are important water sources, contributing 5-15 litres/sec/km2 to summer flows. These form the base flow of most of the Mohaka and Wairoa rivers. Further conversion of indigenous forest to pasture or plantation forest is undesirable because of the high visual and amenity value of the existing vegetation cover, and unlikely because of ownership (much is DOC estate) and difficulty of access.
Contact for Enquiries
Rural Affairs Coordinator
Sector Performance Policy
MAF Policy
Ministry of Agriculture and Forestry
PO Box 2526
Wellington
NEW ZEALAND
Phone: +64 4 894 0675
Fax: +64 4 4 894 0745
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