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Item Towards empirically validated models of soft-rock landslides' occurrence, activity, and sediment delivery : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Science at Massey University, Manawatū, New Zealand(Massey University, 2023) Williams, ForrestWithin New Zealand, soft-rock landslides present a severe hazard to infrastructure and contribute to the degradation of river systems by delivering large amounts of sediment to waterways. Updates to New Zealand’s national policy statement for freshwater management necessitate accurate accounting of freshwater sediment sources, but current sediment budget models do not account for the sediment inputs from soft-rock, and other large slow-moving landslides. To understand which factors lead to the occurrence and continued activity of these landslides and the role they play in New Zealand’s river sediment dynamics, I have completed the following objectives. (i) I have mapped large landslides within the Whanganui-Rangitikei soft-rock hill country in the North Island of New Zealand and conducted a geostatistical analysis to determine which factors control their occurrence. (ii) I have developed a novel remote sensing framework for monitoring large, slow-moving landslides that is based upon time-series Interferometric Synthetic Aperture Radar (InSAR) and time-series sub-Pixel Offset Tracking (sPOT) analyses. Furthermore, I have shown that this framework can identify large landslide activity with an accuracy of 91% and measure the movement of landslides moving with an average velocity of 2.05 m/yr with a mean absolute error of 0.74 m/yr. (iii) I have applied this framework to the landslides of the Whanganui-Rangitikei soft-rock hill country and used its results to perform a geostatistical analysis to determine which factors control a landslide’s current activity state and to estimate the total sediment mass delivered by soft-rock landslides to the rivers of this region. In total, I mapped 1057 large landslides in this region and identified 66 of them as currently active. I find that low slopes, river incision, alignment between bedding planes and slopes, and forest cover are predictive of landslide occurrence, but that low slopes and high annual precipitation rates best predict the current activity states of these landslides. I also find that soft-rock landslides contribute a 10±2% of the total sediment mass delivered to the river systems of this region. Overall, this thesis advances our understanding of why soft-rock landslides occur and provides a framework that will allow future studies to monitor these landslides at region to country-wide scales.Item The influence of rainfall and river incision on the movement rate of a slow-moving, soft-rock landslide in the Rangitikei, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Physical Geography at Massey University, Manawatu Campus, Palmerston North, New Zealand(Massey University, 2018) Holdsworth, Charlotte NaomiThe Rangitikei Slide, a slow-moving landslide near Taihape, New Zealand, was monitored to determine the movement patterns and identify the primary movement drivers. The sediment delivery of landslide material to the Rangitikei River was also estimated to inform the sediment yield from slow-moving landslides connected to a fluvial system. RTK-dGPS monitoring, photogrammetry, and pixel tracking of time-lapse imagery was used to categorise movement patterns, and pixel tracking at different temporal resolutions (weekly and hourly) in conjunction with environmental data identified the drivers and classified the influence on movement. The findings aimed to improve the understanding of these landslide types in New Zealand in order to propose more effective management strategies both locally and around the world. It was found that the landslide comprised several blocks exhibiting different movement rates, and that movement was influenced by a seasonal trend likely from groundwater fluctuations increasing pore pressures in the landslide mass. River erosion by the Rangitikei was identified as a key movement driver and has likely influenced movement since landslide initiation. This was supported by historic aerial imagery and photogrammetry, which showed that the landslide has preserved historic movement phases and these indicate fluvial influence. The estimation of sediment contributions found that ~19,000 t/year of sediment is entering the Rangitikei River from the toe, which is considered a conservative estimate. This contribution is substantial; the Rangitikei Slide is producing almost 3,000 times more sediment per kilometre than the non-landsliding areas of the Rangitikei Catchment. Based on these findings, several management options were proposed for the Rangitikei Slide, with recommendations included for managing slow-moving landslides around the world. It was also evident that further research is needed to better understand slow-moving landslides due to the significant hazard they represent in regard to their sediment contribution to the surrounding environment.Item Economic evaluation of the integrated rehabilitation and management of critical watershed in the Philippines : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Philosophy in Natural Resource and Environmental Economics at Massey University(Massey University, 1995) Umadhay, Gideon AntiojoThe impacts of upper watershed land use practices on resource systems on-site and downstream have long been recognised as a major problem area in resource management in the Philippines. Increasing population levels and upland migration have worsened this problem with time. The consequences are seen in loss of upland productivity, poverty for upland farmers, loss of biodiversity, soil erosion, river siltation, sedimentation of reservoirs and irrigation systems, impacts on estuarine mangroves and coastal fisheries, increased flooding and drought, and so on. There is an urgent need to protect the resource system while at the same time providing for the needs of the upland population. Watershed rehabilitation is proposed as a strategy to achieve this. Watersheds comprise of a sequence of linked resource systems which complicates the integrated rehabilitation and management of them. Management is also complicated by the fact that different agencies have responsibilities over different parts of the watershed and that the private parties within the watershed are there often illegally. Hence, any rehabilitation scheme needs to provide ways to make occupation legal for illegal occupants and at the same time provide incentives for them to cooperate with the rehabilitation strategy. In other words, any proposed scheme must be profitable to the occupants. This study describes a strategy for watershed rehabilitation and analyses a case study example. The project's aim is to integrate social development and watershed rehabilitation. The social development component looks at people participation and the provision of land and opportunities to produce food. The rehabilitation component deals with reforestation and agroforestry to reduce soil degradation and increase water flow. The project involves reforestation of 950 hectares, agroforestry on 3070 hectares, assisted natural regeneration of 716 hectares and production of agricultural crops on an area of 450 hectares. The objectives of the study are to investigate watershed rehabilitation in terms of economic desirability, socio-economic impact and possible implementation constraints. A Benefit-Cost analysis on the data obtained from a feasibility study shows that the project, from an economic point of view. is very worthwhile. The sensitivity analysis further shows that the results are also very robust. Implementation however, will not be an automatic process and the good economic results are not a foregone conclusion. Success of the project will to a large extent depend on cooperation by the occupants of the watershed. Recommendations are made as to how this cooperation can be achieved. Overall however, the study shows that watershed rehabilitation is a strategy that is desirable from an economic and social point of view as well as clearly contributing to sustainable development of the Philippines.Item The clay mineralogy and erosion of the Waipaoa River catchment, Gisborne, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Quaternary Science at Massey University(Massey University, 2002) D'Ath, Michele AnnetteThe Waipaoa River Catchment lies N-NW of Gisborne, covering 2181 km2 it drains south into Poverty Bay 10 km SW of Gisborne. It carries approximately 15 million tonnes of suspended sediment annually, ranking it as one of the most sediment - laden rivers in the world. Deforestation in the early 1900's has led to severe landslide and gully erosion. To assist in catchment analysis and sediment budgeting, Landcare Research divided the Waipaoa River Catchment into 16 land systems, based on the Land Resource Inventory; principally rock type and erosion type and severity. Four of these land systems were chosen to test the hypothesis that clay mineralogy will influence whether landslide or gully erosion is dominant. And, if mineralogical signatures could be established for the different land systems, they could be traced downstream onto the floodplain and into the marine environment. There is no consistent mineralogical difference between the two chosen landslide dominated land systems and the two gully dominated systems. The Mangatu Land System is dominated by gully erosion. Samples taken from the Tarndale Gully complex within the Mangatu Land System for example, are dominated by quartz in the clay fraction, whereas gullies in the Waingaromia Land System are dominated by mica and smectite. The landslide dominated Te Arai Land System, like the Waingaromia Land System, is also primarily mica and smectite, while the clay minerals of the Mako Mako Land System consist of mica and the clay - sized mineral feldspar. It appears that tectonic influence of uplift and faulting, and its influence on headward erosion by streams, is most important in predisposition to gully erosion. The Mangatu Land System dominates the clay mineralogy of both the bedload and suspended sediment of the Waipaoa River at normal flow. However, dilution of this signature does occur at Te Karaka with the influence of the Waingaromia, Waikohu, and Waihora Rivers. In major flood events during high intensity storms, landsliding is more prevalent. Floodplain sediments are thus predominantly soil mantle materials derived from shallow landsliding and bare little resemblance to the dominant Mangatu Land System sediments. Whereas, the Poverty Bay marine core MD2122 sediment, representative of the annual Waipaoa River sediment yield, is produced by the continuous gully erosion. The effect of differential settling gives the core mineralogy a similar signal to that of the floodplain cores; however, sediment is considered to be predominantly Cretaceous material.Item The effects of tillage practices and cropping pattern on nonpoint source pollution and soil quality : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Agricultural Engineering at Massey University(Massey University, 1997) Guo, PengSoil erosion is one of the most serious environmental problems facing world agriculture. In New Zealand, with the current low financial returns from pastoral-based farming, land which was previously unaffected by soil erosion is being intensively farmed and therefore becoming more susceptible to soil erosion and nonpoint source pollution. Adoption of soil resource management and agricultural practices that seek to conserve soil and water resources and minimise environmental degradation is attracting overwhelming interest among scientists and general public. Therefore, the main objective of this study was to assess the effects of selected tillage practices on soil physical properties, soil and water runoff, and water quality under selected cropping pattern. Experiments were conducted on a Ohakea silt loam comparing crop production (barley and oats double crop rotation) using conventional tillage (MP), no-tillage (NT), and pasture (P) (as a control treatment) and assess their impact on erosion and selected soil properties. It was expected that this relatively heavy soil type would be sensitive to cultivation management systems and was therefore suitable for a comparison of tillage methods. The treatments were arranged in a randomised complete block (RCB) design with four blocks of three treatments. In the field experiment, soil bulk density, water content, infiltrability, penetration resistance and earthworm populations were measured during two cropping seasons after barley and oats crops harvest in March and August 1996 respectively. Generally, these soil properties were significantly (P≤ 0.05) affected by tillage practices. Soil water content, infiltrability, and earthworm populations were similar in the NT and P treatments, but significantly higher than those found in the MP treatment. Conversely, soil bulk density at 0 - 50 mm depth was in the order of MP > NT > P. In the laboratory experiment, soil and water runoff, leachate volume, pH and nutrient losses from soil erosion were measured under a rainfall simulator. "Rainfall" intensity used was at an average application rate of 50 mm/hr for one hour, simulating a rainstorm. Mean data from the two experiments suggested that the surface water runoff and soil sediment in runoff were higher in the MP treatment than in the NT and P treatments, and were in the order of MP > NT = P and in a ratio of 4:1:1 and 30:1:1 respectively. Conversely, the volumes of water leachate were higher for the NT and P treatments than for the MP treatment, and in a ratio of 4:1:1 respectively. Soil pH from both water runoff and leachate was at an average of 7.4 and 7.2 respectively, but not different among the three treatments. Nutrient losses in surface water runoff were found to be significantly higher (P≤ 0.05) in the MP treatment (N=1.45 mg/m2, P=1.02 mg/m2, and K=8.3 mg/m2) than those with the NT (N=0.76 mg/m2, P=0.65 mg/m2, and K=6.8 mg/m2). Nutrient losses from NT and pasture treatments were similar. One year's data including two cropping seasons indicate that conventional tillage practices can result in high surface runoff and sediment loss and adversely affect runoff water quality. Such tillage practices are likely to lead to unsustainable land resource management and decreasing crop yields. On the other hand, conservation tillage practices such as no-tillage and continuous pasture cover reduced soil and water erosion, improved soil physical properties and runoff water quality, and conserved land resources leading to enhanced land productivity and agricultural sustainability.Item Wind erosion in Hawke's Bay : the influence of soil aggregate size and cultivation management on sediment flux : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Applied Science (Natural Resource Management) at Massey University(Massey University, 2000) Eastwood, Callum RThe influence of soil aggregate size and cultivation management on sediment flux of two Hawke's Bay soils was investigated. Hawke's Bay Regional Council initiated, and partially funded, the project after they identified wind erosion as a significant land management issue in their region. Wind erosion was simulated on Pakipaki sandy loam (Typic Sandy Recent Soil) and Takapau silt loam (Typic Orthic Allophanic Soil) soil types using a portable wind tunnel. Three different cultivation treatments were applied to research sites on each soil, with eight replicates of each treatment positioned via a split-plot, randomised block trial design. Treatments were designed to produce a range of soil aggregate size distributions. A minimum tillage treatment was also simulated. At each plot, surface (10 mm depth) soil samples were collected for gravimetric moisture content, soil aggregate size and aggregate stability tests. Surface roughness and vegetative cover were measured only on Takapau plots. The Takapau silt loam plots were very susceptible to aggregate breakdown under cultivation, with only a quarter of soil aggregates over 0.85 mm in size after one pass with the cultivator. Two additional passes did not cause a significant change in aggregate size. Minimum tillage on the Takapau plots lead to markedly lower mean sediment flux rates (0.2 gm -1s-1) compared to one pass with a cultivator (3.4 gm-1s-1). The Pakipaki sandy loam exhibited higher resistance to aggregate breakdown compared to Takapau silt loam. After one pass of the cultivator 50 percent of aggregates measured were over 0.85 mm in size, reducing to 45 and 43.3 percent after two and three passes respectively. Data collected from Pakipaki plots suggest decreasing soil aggregate size leads to increasing erosion rates. The relationship was not significant (P<0.05) primarily due to a high variance in results within treatments. Minimum tillage on the Pakipaki sandy loam also resulted in considerably lower mean sediment flux (0.03 gm-1s-1) than the least cultivated plots (1.8 gm-1s-1). The results highlighted some important implications for cultivation management in Hawke's Bay. Use of conventional cultivation techniques on Takapau silt loam soils should be avoided due to the high risk of aggregate breakdown and the subsequent wind erosion risk. Minimum or no-tillage with maximum retention of vegetative residue is the most appropriate for continued arable farming on such soils. In comparison, soil structural characteristics of the Pakipaki sandy loam soil allow for greater manipulation of aggregate size through cultivation However, the sediment flux measured off Pakipaki plots indicates other wind erosion control techniques, such as windbreaks and stubble retention, should be utilised in conjunction w ith maintenance of large aggregate size to adequately control soil wind erosion.Item A DEM based investigation of mass movement sediment delivery : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Soil Science, Massey University(Massey University, 1998) Lovell, Leyton RichardEnvironmental legislation in New Zealand has required local and regional government to place a greater emphasis upon the external effects of land use. For New Zealand hill country this means a quantitative understanding of accelerated soil erosion in terms of its effects upon downstream sedimentation and subsequent flood events. This study was an investigation into the spatial distribution of soil slip erosion (NZLRI) for the Waipaoa River Catchment (~2204km2), East Cape, New Zealand. A combined Remote Sensing and GIS approach using orthorectified aerial photographs and digital elevation models was employed to investigate the topographic attributes influencing the spatial pattern of erosion, utilising a series of classified erosion maps. Of the variables examined, slope, aspect, elevation, and the soil moisture index (SMI) were quantitatively reaffirmed as controlling influences upon mass movement. The erosion maps in conjunction with hydrological flow accumulation images were also found to objectively determine thresholds for identifying stream channel networks from the DEM. The erosion maps when combined with historical data were used to construct sediment delivery ratios and sediment budgets for each landsystem investigated. The most significant influences upon landsliding were combined in a data driven model to assign a probability of landsliding for each pixel, which can later be used to create landslide susceptibility maps and assist in the allocation of soil conservation resources. Keywords: ORTHORECTIFIED AERIAL PHOTOGRAPHS, DEMs, SOIL SLIP EROSION, SEDIMENT DELIVERY RATIOS, SEDIMENT BUDGETSItem A hydrological comparison between two watersheds in Pohangina County : a thesis submitted in partial fulfillment of the requirements for the degree of Master of Agricultural Science at Massey University(Massey University, 1973) Rolston, Shirley JeanThe study area consists of two adjacent catchments situated on the unconsolidated Castlecliffian Sand country in the Pohangina County. This parent material was first recognized as an erosion problem with respect to canyon gullying in the middle 1930s, and since the late 1940s has been an area of major concern for the Manawatu Catchment Board. Various conservation structures and extensive planting of different exotic tree species, coupled with improved pasture and stock management, have resulted in the near stabilization of some of the watersheds in the district. Other watersheds are still contributing unknown quantities of sediment to the Oroua and Pohangina Rivers in each runoff event. This study, although mainly qualitative in approach, endeavours to compare the sediment loads produced at peak runoff times in 1972 by the two study catchments. Flood level recorders were installed to provide an indication of the peak levels reached by flood waters. With the simple equipment available, flood water samples were taken as near to the flood peak as could be judged. Mechanical analyses carried out on these samples determined the proportions of coarse sand, fine sand, silt and clay in the sediment load.Item Surface erosion characteristics of three Manawatu soils : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Soil Science at Massey University(Massey University, 1992) Grant, LachlanSheet erosion is the most extensively mapped erosion type in New Zealand. With the current financial returns from pastoral framing, land which was previously unaffected by sheet erosion is being cultivated and therefore becoming more susceptible to sheet erosion. The main objective of this study was to assess quantitatively, under the same conditions of slope, cover, and rainfall, the erodibility of three soils which are suitable for either arable farming or market gardening. Whether the eroded sediment consisted of sand, silt or clay particles, or more predominantly aggregates of these primary particles was also determined. The three soils examined were from the Manawatu region and included the Kiwitea silt loam (Dystrochrept), Levin silt loam (Dystrochrept) and the Tokomaru silt loam (Fragiaqualf). A portable rainfall simulator was used to generate runoff and sediment from soil packed in 0.2 m2 trays. All "storms" were for 60 minutes in which 65 mm of rain was applied. Particle selectively was determined using pipette analysis methods and a settling tube. Quantitatively comparing the erodibility of the three soils, it was found that the Levin soil was the most erodible and the Kiwitea was the least erodible. If the same storm intensity and soil conditions were to occur over a large area, one hectare could produce 6.4, 17.6 and 10.3 tonnes of sediment from the Kiwitea, Levin and Tokomaru soils respectively. Soil particles and aggregates were selectively removed by rainsplash and overland flow. The proportion of sand particles present in the eroded sediment was always lower than the original soil due to the inability of sand particles to be entrained by overland flow. Silt particles were easily detached and were most commonly eroded as individual particles. Clay particles were eroded and transported in the form of aggregates, a result of their binding properties. The size distribution of eroded sediment became progressively coarser over the rainfall period. This was because initially there was insufficient runoff energy available to transport the larger particles. A vegetative cover severely reduces the volume of runoff and the amount of sediment eroded by cushioning the raindrop impact.Item The use of a geographic information system to investigate soil slip distribution and the land use capability classification in the East Coast region, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Soil Science at Massey University(Massey University, 1995) Hendriksen, Sheryl DeniseThe land of the North Island East Coast region has such a severe erosion problem that in some places the current land use cannot be sustained. The expansion of exotic forestry in the region will provide protection for the land, regional growth and development, and employment, but it also brings competition for good land. The New Zealand Resource Management Act, 1991, aims to promote sustainable use of our resources and requires regulatory authorities to monitor the state of their natural resources and to follow the principles set in the RMA when developing land use policies. Remotely sensed data provides a timely and accurate assessment of surface features. Aerial photography provides a better delineation of soil slip erosion than satellite imagery. Geographic Information Systems facilitate the storage and display of resource information. Through manipulation of GIS data layers, relationships between the distribution of soil slip erosion following Cyclone Bola, 1988, and other physical factors are investigated. The density of soil slip increases with increasing slope angle to a maximum on slopes of 30°. The amount of soil slip depends on the underlying rock type with jointed mudstone having the highest density. Most soil slip erosion occurs on NE, N, NW, and E facing slopes, but the reason for this cannot be attributed to either slope angle or rock type. The Land Use Capability classification is currently used by land use managers and planners to describe the land in terms of its limitation to productive uses. The detail of information in the New Zealand Land Resource Inventory LUC classification can be improved by incorporating more detailed slope angle and slope aspect information derived from digital contour data.