• Title/Summary/Keyword: expected value

Search Result 3,527, Processing Time 0.047 seconds

Text Mining-Based Emerging Trend Analysis for the Aviation Industry (항공산업 미래유망분야 선정을 위한 텍스트 마이닝 기반의 트렌드 분석)

  • Kim, Hyun-Jung;Jo, Nam-Ok;Shin, Kyung-Shik
    • Journal of Intelligence and Information Systems
    • /
    • v.21 no.1
    • /
    • pp.65-82
    • /
    • 2015
  • Recently, there has been a surge of interest in finding core issues and analyzing emerging trends for the future. This represents efforts to devise national strategies and policies based on the selection of promising areas that can create economic and social added value. The existing studies, including those dedicated to the discovery of future promising fields, have mostly been dependent on qualitative research methods such as literature review and expert judgement. Deriving results from large amounts of information under this approach is both costly and time consuming. Efforts have been made to make up for the weaknesses of the conventional qualitative analysis approach designed to select key promising areas through discovery of future core issues and emerging trend analysis in various areas of academic research. There needs to be a paradigm shift in toward implementing qualitative research methods along with quantitative research methods like text mining in a mutually complementary manner. The change is to ensure objective and practical emerging trend analysis results based on large amounts of data. However, even such studies have had shortcoming related to their dependence on simple keywords for analysis, which makes it difficult to derive meaning from data. Besides, no study has been carried out so far to develop core issues and analyze emerging trends in special domains like the aviation industry. The change used to implement recent studies is being witnessed in various areas such as the steel industry, the information and communications technology industry, the construction industry in architectural engineering and so on. This study focused on retrieving aviation-related core issues and emerging trends from overall research papers pertaining to aviation through text mining, which is one of the big data analysis techniques. In this manner, the promising future areas for the air transport industry are selected based on objective data from aviation-related research papers. In order to compensate for the difficulties in grasping the meaning of single words in emerging trend analysis at keyword levels, this study will adopt topic analysis, which is a technique used to find out general themes latent in text document sets. The analysis will lead to the extraction of topics, which represent keyword sets, thereby discovering core issues and conducting emerging trend analysis. Based on the issues, it identified aviation-related research trends and selected the promising areas for the future. Research on core issue retrieval and emerging trend analysis for the aviation industry based on big data analysis is still in its incipient stages. So, the analysis targets for this study are restricted to data from aviation-related research papers. However, it has significance in that it prepared a quantitative analysis model for continuously monitoring the derived core issues and presenting directions regarding the areas with good prospects for the future. In the future, the scope is slated to expand to cover relevant domestic or international news articles and bidding information as well, thus increasing the reliability of analysis results. On the basis of the topic analysis results, core issues for the aviation industry will be determined. Then, emerging trend analysis for the issues will be implemented by year in order to identify the changes they undergo in time series. Through these procedures, this study aims to prepare a system for developing key promising areas for the future aviation industry as well as for ensuring rapid response. Additionally, the promising areas selected based on the aforementioned results and the analysis of pertinent policy research reports will be compared with the areas in which the actual government investments are made. The results from this comparative analysis are expected to make useful reference materials for future policy development and budget establishment.

Interpretation of Interaction of Herbicides on Principal Paddy Weeds - By Use of Oxyfluorfen and Bensulfuron-methyl Data - (주요(主要) 논 잡초종(雜草種)에 대한 제초제간(除草劑間)의 상호작용효과(相互作用效果) 해석연구(解析硏究) - Oxyfluorfen과 Bensulfuron을 예(例)로 -)

  • Han, J.H.;Guh, J.O.;Chon, S.U.;Kwon, O.D.
    • Korean Journal of Weed Science
    • /
    • v.12 no.2
    • /
    • pp.144-157
    • /
    • 1992
  • The study was conducted to compare the interprete methods and examine the feasibility of mixture use of oxyfluorfen and bensulfuron in controlling principal Paddy weeds, annuals and perennials. Application ratio of both chemicals were obtained from the combinations of 5 levels(0, 5, 10, 15, 20 g ai/ha) of each chemicals, respectively. All the treatments were applied at 5 days after transplanting and water was maintained at 3.0cm in depth. Shoot fresh-weight of weeds was assessed at 35 days after treatments. Data obtained was analysed by Colby, Isobole, Calculus, Regression and EQM method, respectively. The results from the analysis of variance on the principal weeds treated with oxyfluorfen and bensulfuron showed significant interactions at 1% level on both Echinochloa crus-galli and Eleocharis Kuroguwai, and total species at 0.5% level on both Potamogeton distinctus and Cyperus serotinus, but non significant on Scirpus juncoides and Sagittaria pygmaea. Thereafter, the results of the models applied to Echinochloa crus-galli, Eleocharis kuroguwai and total species were as follows ; 1. The Colby method gave values nearly identical to regression estimate method (both multiplicative models) as provided by Akobundu et al. The Colby method and Regression method indicated synergistic toward Echinochloa curs-galli, and total species, but antagonistic toward Eleocharis kuroguwai. 2. The Isobole method shows synergism on Echinochloa crus-galli at $ID_{50}$, and total species at $ID_{60}$ on Eleochari kuroguwai. 3. The Calculus method gave positive signs for the first differentiation and negative signs for the second differentiation except for some rates on Echinochloa crus-galli and total species, but reverse on Eleocharis kuroguwai. These result does not agree with the observed values. 4. ${\theta}$ value from the EQM method was greater than one at all combinations. This result was quite different from those of other methods. 5. The various models did not show the same results, but mixture of oxyfluorfen and bensulfuron tend to have synergistic effect. Weeding effect also was high. Treatment in terms of two chemical combination was expected to reduce rates, and to enhence weeding efficacy compared with single treatment.

  • PDF

Dose Alterations at the Distal Surface by Tissue Inhomogeneity in High Energy Photon Beam (조직 불균질성에 의한 고에너지 광자선의 선량변화)

  • Kim, Young-Ai;Choi, Tae-Jin;Kim, Ok-Bae
    • Radiation Oncology Journal
    • /
    • v.13 no.3
    • /
    • pp.277-283
    • /
    • 1995
  • Purpose : This study was performed to measure dose alteration at the air-tissue interface resulting from rebuild-up to the loss of charged particle equilibrium in the tissues around the air-tissue interfaces. Materials and Methods : The 6 and 10-MV photon beam in dual energy linear accelerator were used to measure the surface dose at the air-tissue interface The polystyrene phantom sized $25{\times}25{\times}5\;cm^3$ and a water phantom sized $29{\times}29{\times}48\;cm^3$ which incorporates a parallel-plate ionization chamber in the distal side of air gap were used in this study. The treatment field sizes were $5{\times}5\;cm^2,\;10{\times}10\;cm^2\;and\;20{\times}20\;cm^2$. Air cavity thickness was variable from 10 mm to 50 mm. The observed-expected ratio (OER) was defined as the ratio of dose measured at the distal junction that is air-tissue interface to the dose measured at the same point in a homogeneous phantom. Results : In this experiment, the result of OER was close or slightly over than 1.0 for the large field size but much less (about 0.565) than 1.0 for the small field size in both photon energy. The factors to affect the dose distribution at the air-tissue interface were the field size, the thickness of air cavity. and the photon energy. Conclusion : Thus, the radiation oncologist should take into account dose reduction at the air-tissue interface when planning the head and neck cancer especially pharynx and laryngeal lesions, because the dose can be less nearly $29{\%}$ than predicted value.

  • PDF

The Effects of LBS Information Filtering on Users' Perceived Uncertainty and Information Search Behavior (위치기반 서비스를 통한 정보 필터링이 사용자의 불확실성과 정보탐색 행동에 미치는 영향)

  • Zhai, Xiaolin;Im, Il
    • Asia pacific journal of information systems
    • /
    • v.24 no.4
    • /
    • pp.493-513
    • /
    • 2014
  • With the development of related technologies, Location-Based Services (LBS) are growing fast and being used in many ways. Past LBS studies have focused on adoption of LBS because of the fact that LBS users have privacy concerns regarding revealing their location information. Meanwhile, the number of LBS users and revenues from LBS are growing rapidly because users can get some benefits by revealing their location information. Little research has been done on how LBS affects consumers' information search behavior in product purchase. The purpose of this paper is examining the effect of LBS information filtering on buyers' uncertainty and their information search behavior. When consumers purchase a product, they try to reduce uncertainty by searching information. Generally, there are two types of uncertainties - knowledge uncertainty and choice uncertainty. Knowledge uncertainty refers to the lack of information on what kinds of alternatives are available in the market and/or their important attributes. Therefore, consumers having knowledge uncertainty will have difficulties in identifying what alternatives exist in the market to fulfil their needs. Choice uncertainty refers to the lack of information about consumers' own preferences and which alternative will fit in their needs. Therefore, consumers with choice uncertainty have difficulties selecting best product among available alternatives.. According to economics of information theory, consumers narrow the scope of information search when knowledge uncertainty is high. It is because consumers' information search cost is high when their knowledge uncertainty is high. If people do not know available alternatives and their attributes, it takes time and cognitive efforts for them to acquire information about available alternatives. Therefore, they will reduce search breadth. For people with high knowledge uncertainty, the information about products and their attributes is new and of high value for them. Therefore, they will conduct searches more in-depth because they have incentive to acquire more information. When people have high choice uncertainty, people tend to search information about more alternatives. It is because increased search breadth will improve their chances to find better alternative for them. On the other hand, since human's cognitive capacity is limited, the increased search breadth (more alternatives) will reduce the depth of information search for each alternative. Consumers with high choice uncertainty will spend less time and effort for each alternative because considering more alternatives will increase their utility. LBS provides users with the capability to screen alternatives based on the distance from them, which reduces information search costs. Therefore, it is expected that LBS will help users consider more alternatives even when they have high knowledge uncertainty. LBS provides distance information, which helps users choose alternatives appropriate for them. Therefore, users will perceive lower choice uncertainty when they use LBS. In order to test the hypotheses, we selected 80 students and assigned them to one of the two experiment groups. One group was asked to use LBS to search surrounding restaurants and the other group was asked to not use LBS to search nearby restaurants. The experimental tasks and measures items were validated in a pilot experiment. The final measurement items are shown in Appendix A. Each subject was asked to read one of the two scenarios - with or without LBS - and use a smartphone application to pick a restaurant. All behaviors on smartphone were recorded using a recording application. Search breadth was measured by the number of restaurants clicked by each subject. Search depths was measured by two metrics - the average number of sub-level pages each subject visited and the average time spent on each restaurant. The hypotheses were tested using SPSS and PLS. The results show that knowledge uncertainty reduces search breadth (H1a). However, there was no significant correlation between knowledge uncertainty and search depth (H1b). Choice uncertainty significantly reduces search depth (H2b), but no significant relationship was found between choice uncertainty and search breadth (H2a). LBS information filtering significantly reduces the buyers' choice uncertainty (H4) and reduces the negative relationship between knowledge uncertainty and search breadth (H3). This research provides some important implications for service providers. Service providers should use different strategies based on their service properties. For those service providers who are not well-known to consumers (high knowledge uncertainty) should encourage their customers to use LBS. This is because LBS would increase buyers' consideration sets when the knowledge uncertainty is high. Therefore, less known services have chances to be included in consumers' consideration sets with LBS. On the other hand, LBS information filtering decrease choice uncertainty and the near service providers are more likely to be selected than without LBS. Hence, service providers should analyze geographically approximate competitors' strength and try to reduce the gap so that they can have chances to be included in the consideration set.

Research Trend of Biomass-Derived Engineering Plastics (바이오매스 기반 엔지니어링 플라스틱 연구 동향)

  • Jeon, Hyeonyeol;Koo, Jun Mo;Park, Seul-A;Kim, Seon-Mi;Jegal, Jonggeon;Cha, Hyun Gil;Oh, Dongyeop X.;Hwang, Sung Yeon;Park, Jeyoung
    • Applied Chemistry for Engineering
    • /
    • v.31 no.2
    • /
    • pp.115-124
    • /
    • 2020
  • Sustainable plastics can be mainly categorized into (1) biodegradable plastics decomposed into water and carbon dioxide after use, and (2) biomass-derived plastics possessing the carbon neutrality by utilizing raw materials converted from atmospheric carbon dioxide to biomass. Recently, biomass-derived engineering plastics (EP) and natural nanofiber-reinforced nanocomposites are emerging as a new direction of the industry. In addition to the eco-friendliness of natural resources, these materials are competitive over petroleum-based plastics in the high value-added plastics market. Polyesters and polycarbonates synthesized from isosorbide and 2,5-furandicarboxylic acid, which are representative biomass-derived monomers, are at the forefront of industrialization due to their higher transparency, mechanical properties, thermal stability, and gas barrier properties. Moreover, isosorbide has potential to be applied to super EP material with continuous service temperature over 150 ℃. In situ polymerization utilizing surface hydrophilicity and multi-functionality of natural nanofibers such as nanocellulose and nanochitin achieves remarkable improvements of mechanical properties with the minimal dose of nanofillers. Biomass-derived tough-plastics covered in this review are expected to replace petroleum-based plastics by satisfying the carbon neutrality required by the environment, the high functionality by the consumer, and the accessibility by the industry.

Monitoring of Sulfur Dioxide, Carotenoid Contents and Bacillus cereus Contamination of Dried Sweet Potato in Circulating Dried Agricultural Products (국내 유통 건조 농산물 중 고구마 말랭이의 이산화황, 카로티노이드 함량 및 바실러스 세레우스오염 정도 조사)

  • Lee, Hyeon Min;Park, Hyun Ji;Kim, Ji Na;Shin, Weon Sun;Kim, Eun Mi
    • Journal of Food Hygiene and Safety
    • /
    • v.32 no.6
    • /
    • pp.477-484
    • /
    • 2017
  • This study was conducted to investigate the content of sulfur dioxide, carotenoids and the degree of contamination of Bacillus cereus in 33 kinds of dried sweet potato from domestic mainly dried agricultural products in Korea. According to the characteristics of dried sweet potato samples, it was classified into four clusters and as a result of analyzing the contents of sulfur dioxide, carotenoids and the degree of contamination B. cereus was no significant difference among the clusters. The detection ranges of residual sulfur dioxide from 33 dried sweet potatoes ranged from 0.38 to 28.16 mg/kg, three cases (9.09%) were detected at the reference level of 10 mg/kg or more. But no samples exceeding 30 mg/kg, the tolerance level of sulfur dioxide in dried sweet potatoes were detected. Since dried sweet potato does not have a standard for carotenoids, when comparing the national and international standards of carotenoids, the range of detection of carotenoids in dried sweet potato was $46{\sim}2,663{\mu}g$/100 g, which was within the reference range of $0{\sim}9,826{\mu}g$/100 g. In principle colonies suspected to be B. cereus in dried sweet potato were not detected. In 7 cases (21.21%), there were detected in the range of 0.05~1.59 log CFU/g but not more than 3 log CFU/g as the reference value. The results of this study are expected to be used as basic data to establish quality standard for dried sweet potatoes. In order to control the quality of dried sweet potatoes in domestic market, raw materials, drying method and packaging after distribution, it is necessary to maintain and maintain the process steadily.

Agricultural and Marine By-Products Fermented Diet and Its Economic Value in Pigs (농수부산물 발효사료가 양돈에 미치는 경제적 효과 분석)

  • Chu, Gyo-Moon;Kim, Hoi-Yun;Ha, Ji-Hee;Yang, Jeong-Mo;Yang, Bo-Seock;Park, Cheol-Jin;Song, Young-Min
    • Journal of agriculture & life science
    • /
    • v.46 no.3
    • /
    • pp.59-68
    • /
    • 2012
  • This study was conducted to investigate the economic analysis of fermented diet made of agricultural and marine by-products such as, dropped apples, persimmon shells, mushroom (Flammulina velutipes) by-products, king oyster mushroom by-products and brewer's grain in Berkshire or crossed pigs. The daily diet cost were decreased by 2.16~3.44%, 3.83~13.35% and 7.47~41.61% when fermented dropped apples diet, fermented persimmon shells diet and fermented mushroom (F. velutipes) by-products diet were fed to Berkshire pigs. The daily feed cost was also decreased by 1.59~4.05% and 59.09~66.90% when fermented king oyster mushroom by-products diet and fermented brewer's grain diet were fed to crossed pigs. Carcass prices were increased by 3.09%, 1.20~3.40% and 1.13% when 2% fermented dropped apples diet, fermented persimmon shells diet and 0.5~1.0% fermented mushroom (F. velutipes) by-products diet were fed to Berkshire pigs. Carcass prices were increased by 2.87~4.19% and 41.31~49.14% when fermented king oyster mushroom by-products diet and fermented brewer's grain were fed to crossed pigs. Therefore, fermented agro by-products diet of dropped apples, persimmon shells, king oyster mushroom, mushroom (F. velutipes) and brewer's grain was expected to improve swine farms income due to decreased diet cost and increased carcass prices in Berkshire pigs or crossed pigs.

Literary Text and the Cultural Interpretation - A Study of the Model of 「History of Spanish Literature」 (문학텍스트와 문학적 해석 -「스페인 문학사」를 통한 모델 연구)

  • Na, Songjoo
    • Cross-Cultural Studies
    • /
    • v.26
    • /
    • pp.465-485
    • /
    • 2012
  • Instructing "History of Spanish Literature" class faces various types of limits and obstacles, just as other foreign language literature history classes do. Majority of students enter the university without having any previous spanish learning experience, which means, for them, even the interpretation of the text itself can be difficult. Moreover, the fact that "History of Spanish Literature" is traced all the way back to the Middle Age, students encounter even more difficulties and find factors that make them feel the class is not interesting. To list several, such factors include the embarrassment felt by the students, antiquated expressions, literature texts filled with deliberately broken grammars, explanations written in pretentious vocabularies, disorderly introduction of many different literary works that ignores the big picture, in which in return, reduces academic interest in students, and finally general lack of interest in literate itself due to the fact that the following generation is used to visual media. Although recognizing such problem that causes the distortion of the value of our lives and literature is a very imminent problem, there has not even been a primary discussion on such matter. Thus, the problem of what to teach in "History of Spanish Literature" class remains unsolved so far. Such problem includes wether to teach the history of authors and literature works, or the chronology of the text, the correlations, and what style of writing to teach first among many, and how to teach to read with criticism, and how to effectively utilize the limited class time to teach. However, unfortunately, there has not been any sorts of discussion among the insructors. I, as well, am not so proud of myself either when I question myself of how little and insufficiently did I contemplate about such problems. Living in the era so called the visual media era or the crisis of humanity studies, now there is a strong need to bring some change in the education of literature history. To suggest a solution to make such necessary change, I recommended to incorporate the visual media, the culture or custom that students are accustomed to, to the class. This solution is not only an attempt to introduce various fields to students, superseding the mere literature reserch area, but also the result that reflects the voice of students who come from a different cultural background and generation. Thus, what not to forget is that the bottom line of adopting a new teaching method is to increase the class participation of students and broaden the horizon of the Spanish literature. However, the ultimate goal of "History of Spanish Literature" class is the contemplation about humanity, not the progress in linguistic ability. Similarly, the ultimate goal of university education is to train students to become a successful member of the society. To achieve such goal, cultural approach to the literature text helps not only Spanish learning but also pragmatic education. Moreover, it helps to go beyond of what a mere functional person does. However, despite such optimistic expectations, foreign literature class has to face limits of eclecticism. As for the solution, as mentioned above, the method of teaching that mainly incorporates cultural text is a approach that fulfills the students with sensibility who live in the visual era. Second, it is a three-dimensional and sensible approach for the visual era, not an annotation that searches for any ambiguous vocabularies or metaphors. Third, it is the method that reduces the burdensome amount of reading. Fourth, it triggers interest in students including philosophical, sociocultural, and political ones. Such experience is expected to stimulate the intellectual curiosity in students and moreover motivates them to continues their study in graduate school, because it itself can be an interesting area of study.

Fantasy and educational meaning of Sukhyangjeon - A relationship between notice of hardships and fantasy (<숙향전>의 환상성과 교육적 의의 -'고난의 예고'와 환상의 관계를 중심으로-)

  • Lee, Hyo-jung
    • Journal of Korean Classical Literature and Education
    • /
    • no.34
    • /
    • pp.41-74
    • /
    • 2017
  • This study aimed to investigate the narrative strategy and meaning of fantasy in classic novels and to derive the educational meaning from the fantasy of Sukhyangjeon. This study selected Sukhyangjeon because is considered a suitable literary text that embodies characteristics of fantasy inherent in classical novels through its successful portrayal of the fantasy genre and its high popularity during its time. Specifically, this study observed that the "notice of hardships" which repeatedly appears in the narration of Sukhyangjeon reinforces the fantasy of the novel as it serves as an advance notice of intervention from heaven. Therefore, this study investigated the relationship between the notice of hardships and fantasy by focusing on Sukhyang's life. The way in which the "notice of hardships" is a form of illusion realized it evident in the plot when heaven saves Sukhyang from her hardship even though it was heaven that had granted her those forms of hardship. Firstly, the "notice from heaven" constitutes the macro structure of Sukhyangjeon. Through it, readers realize the enormous power of heaven by seeing how Sukhyang's life has been realized in accordance with heaven's notice with that, it evokes a sense of respect to heaven. In addition, heaven saves Sukhyang from different forms of danger. It enhances a miraculous feeling, which the omnipotent power of heaven shows, against the innocent appearance of Sukhyang during her times of danger. Meanwhile, when heaven notifies Sukhyang and the surrounding people of their fate and subsequently realizes it through dreams, this act creates a mysterious atmosphere and improves the probability of the narrative. If so, the narrative meaning in reinforcing the fantasy of the novel by the use of "notice of hardships" could be revealed through Sukhyang's real life. First, the hardship in which Sukhyang has gone through is so realistic and detailed that the readers' feelings of empathy are evoked with the fear of the coming hardship, wailing together, and trying to resolve the inner anxiety through Sukhyang's happiness. Second, the heavenly beings who are touched by the good behaviors of Sukhyang save her from the dangers of death. This creates the belief in readers that heaven intervenes for the good people. Third, the active attitude that Sukhyang and Leesun show in the process of marriage helps them overcome their earthly hardship and preserve their relationship in heaven. This gives readers hope that they could go to a "higher life" after going through suffering. This fantasy of Sukhyangjeon helps readers overcome their anxieties of reality through fantasy and recognizes the importance of relationships to enhance a sense of unity and solidarity with others. Because of these elements, it is expected that the fantasy of Sukhyangjeon will have a meaningful value to modern readers.

How effective has the Wairau River erodible embankment been in removing sediment from the Lower Wairau River?

  • Kyle, Christensen
    • Proceedings of the Korea Water Resources Association Conference
    • /
    • 2015.05a
    • /
    • pp.237-237
    • /
    • 2015
  • The district of Marlborough has had more than its share of river management projects over the past 150 years, each one uniquely affecting the geomorphology and flood hazard of the Wairau Plains. A major early project was to block the Opawa distributary channel at Conders Bend. The Opawa distributary channel took a third and more of Wairau River floodwaters and was a major increasing threat to Blenheim. The blocking of the Opawa required the Wairau and Lower Wairau rivers to carry greater flood flows more often. Consequently the Lower Wairau River was breaking out of its stopbanks approximately every seven years. The idea of diverting flood waters at Tuamarina by providing a direct diversion to the sea through the beach ridges was conceptualised back around the 1920s however, limits on resources and machinery meant the mission of excavating this diversion didn't become feasible until the 1960s. In 1964 a 10 m wide pilot channel was cut from the sea to Tuamarina with an initial capacity of $700m^3/s$. It was expected that floods would eventually scour this 'Wairau Diversion' to its design channel width of 150 m. This did take many more years than initially thought but after approximately 50 years with a little mechanical assistance the Wairau Diversion reached an adequate capacity. Using the power of the river to erode the channel out to its design width and depth was a brilliant idea that saved many thousands of dollars in construction costs and it is somewhat ironic that it is that very same concept that is now being used to deal with the aggradation problem that the Wairau Diversion has caused. The introduction of the Wairau Diversion did provide some flood relief to the lower reaches of the river but unfortunately as the Diversion channel was eroding and enlarging the Lower Wairau River was aggrading and reducing in capacity due to its inability to pass its sediment load with reduced flood flows. It is estimated that approximately $2,000,000m^3$ of sediment was deposited on the bed of the Lower Wairau River in the time between the Diversion's introduction in 1964 and 2010, raising the Lower Wairau's bed upwards of 1.5m in some locations. A numerical morphological model (MIKE-11 ST) was used to assess a number of options which led to the decision and resource consent to construct an erodible (fuse plug) bank at the head of the Wairau Diversion to divert more frequent scouring-flows ($+400m^3/s$)down the Lower Wairau River. Full control gates were ruled out on the grounds of expense. The initial construction of the erodible bank followed in late 2009 with the bank's level at the fuse location set to overtop and begin washing out at a combined Wairau flow of $1,400m^3/s$ which avoids berm flooding in the Lower Wairau. In the three years since the erodible bank was first constructed the Wairau River has sustained 14 events with recorded flows at Tuamarina above $1,000m^3/s$ and three of events in excess of $2,500m^3/s$. These freshes and floods have resulted in washout and rebuild of the erodible bank eight times with a combined rebuild expenditure of $80,000. Marlborough District Council's Rivers & Drainage Department maintains a regular monitoring program for the bed of the Lower Wairau River, which consists of recurrently surveying a series of standard cross sections and estimating the mean bed level (MBL) at each section as well as an overall MBL change over time. A survey was carried out just prior to the installation of the erodible bank and another survey was carried out earlier this year. The results from this latest survey show for the first time since construction of the Wairau Diversion the Lower Wairau River is enlarging. It is estimated that the entire bed of the Lower Wairau has eroded down by an overall average of 60 mm since the introduction of the erodible bank which equates to a total volume of $260,000m^3$. At a cost of $$0.30/m^3$ this represents excellent value compared to mechanical dredging which would likely be in excess of $$10/m^3$. This confirms that the idea of using the river to enlarge the channel is again working for the Wairau River system and that in time nature's "excavator" will provide a channel capacity that will continue to meet design requirements.

  • PDF