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Forested watersheds have often been managed for flood mitigation. Studies have shown that forests have the potential to minimize peak flows during storm events, yet the relationship between forests and flooding is inexact. Forest roads, usually found in managed systems, can potentially magnify the effects of forest harvesting on water yields. A distributed hydrologic model (DHSVM) was calibrated for a 760 ha watershed in the Blue Ridge Mountains of North Carolina. The impacts of forest road density were evaluated by running the model using uniform input parameters but changing road densities. Road densities tested were 0.5, 1.0, 3.0, 4.3, 6.0 and 12.0 km km-2. Results indicate that increases in road density increased average streamflows at densities ≥ 4.3 km km-2. During small storm events, discharge was impacted at densities ≥ 6.0 km km-2 and streamflows were impacted during large rainfall events ≥ 3.0 km km-2 road densities. These findings indicate that forest roads can influence water yields and additional management efforts may be needed that can slow the water yield from forest roads. / Master of Science

Submitted in fulfillment of the academic requirements for the degree of Doctor of Engineering: Civil Engineering and Surveying, Durban University of Technology. Durban. South Africa, 2015. / Among various gravel roads distress prediction models in existence, a gravel loss prediction model is considered critical in selecting the optimal re-gravelling schedule for effective maintenance management of gravel roads. However, due to the number of variables contributing to deterioration of gravel roads and hence gravel loss, gravel loss prediction models are not readily transferable from one geographical location to another, particularly if the locations in question differ in climatic condition, gravel material characteristics, quality of construction and maintenance, terrain, traffic characteristics and driver behaviours. Addressing the aforementioned local characteristics pose a challenge to existing international gravel loss prediction models when employed locally, resulting in inaccurate prediction of gravel loss. Hence the need for a gravel loss prediction model to be formulated locally so as to address local characteristics influencing gravel roads deterioration. The main objective of this study was to formulate locally, a statistically accurate gravel loss prediction model for marginal gravel materials employed to surface gravel roads in Iringa region. The intention was to address local characteristics influencing gravel roads deterioration in the region. To promote research on gravel roads management, the author has published seven papers and presented ten papers in established journals and conferences respectively, as indicated in the Appendix 13. It is author expectation that, given the right impetus, locally formulated gravel loss prediction models can be incorporated, as one of a tool, in gravel roads management systems (GRMS). The literature review focused on the gravel road condition surveys, modelling exercises, gravel loss, and a review of existing gravel loss prediction models. The literature review also examined the version of GRMS currently practiced in Tanzania by its road organizations. The study used factorial experimental design. Parameters which are deemed to influence the gravel loss were collected and studied. A questionnaire was used to study the status of gravel road MMS in Tanzania. The data obtained from the questionnaire responses were analysed with the aid of Statistical Package for Social Sciences (SPSS) and Microsoft Excel. A detailed gravel road condition survey of each 300 m long test section was carried out during site visits. The measurement of gravel loss through the change in average height loss formed a crucial part of the study. The modelling of a gravel loss prediction model was performed using pavemetric principles, the term coined by this study, which is principally based on econometric principles. From the analysis of questionnaire responses, it was evident that each Tanzania Roads Agency (TANROADS) regional office and district council works department needs to have a unique MMS and GRMS which reflect their operating capacity. The results of the condition survey led to the formulation of a new range of grading coefficient (GC) to suit the local marginal materials. The gravel loss survey results assisted in establishing gravel loss thresholds. The thresholds were based on the rate of gravel loss noted in the study. These thresholds can be employed to enhance the quality control of gravel roads construction and maintenance practices. The study formulated a gravel loss prediction model for Iringa region. The process utilized average daily traffic, climate, and derivatives of sieve analysis and Atterberg limits. The model is statistically significant at 1 % level. The model gives a constant gravel loss of 0.1 mm per annum regardless the state of the six variables in the model. This was attributed to autonomous loss that is the amount of gravel material lost through mechanical and chemical weathering. Recommendations include the need for gravel loss prediction models to reflect local characteristics influencing the deterioration of the gravel roads in question and the modelling capacity of local road agencies. Areas for further studies are highlighted.

published_or_final_version / Transport Policy and Planning / Master / Master of Arts

As estradas municipais constituem a parcela preponderante, desde um ponto de vista de extensão, da malha viária do Estado do Rio Grande do Sul. As atividades desenvolvidas implicam em dispêndios de parcelas significativas do orçamento, para a maior parte dos municípios. Em que pese esta importância, o padrão gerencial aplicado é precário, tanto do ponto de vista do desenvolvimento tecnológico quanto de controles administrativos e de custos. Neste trabalho são estabelecidas bases de um sistema de gerência de estradas municipais do Estado do Rio Grande do Sul, adequado à realidade dos municípios. Foi visada a racionalização das atividades através de uma melhor aplicação dos recursos disponíveis e a melhoria progressiva da malha viária. Em caráter preliminar é indicada uma nova especificação para a escolha de materiais para revestimento primário, atendendo às peculiaridades dos materiais tropicais. / County roads represent an important share of the total extension of the road network in Rio Grande do Sul, one of the Brazilian states. In most municipalities, the activities of these roads take a significant part of their budgets. Even so, the management strategies used are deficient, either from a technological development perspective or from the administrative controls and costs viewpoint. In this work the bases of a management system are proposed, adapted to the reality of the county roads found in the municipalities studied. The main feature of the system is the rationalization of the maintenance, improvement and construction activities, assuring a better use of the available resources and a progressive improvement of the road network. A new specification for the materials for unpaved roads is presented in a preliminary sense, based on the peculiarities of the materials usually found in tropical regions.

As estradas municipais constituem a parcela preponderante, desde um ponto de vista de extensão, da malha viária do Estado do Rio Grande do Sul. As atividades desenvolvidas implicam em dispêndios de parcelas significativas do orçamento, para a maior parte dos municípios. Em que pese esta importância, o padrão gerencial aplicado é precário, tanto do ponto de vista do desenvolvimento tecnológico quanto de controles administrativos e de custos. Neste trabalho são estabelecidas bases de um sistema de gerência de estradas municipais do Estado do Rio Grande do Sul, adequado à realidade dos municípios. Foi visada a racionalização das atividades através de uma melhor aplicação dos recursos disponíveis e a melhoria progressiva da malha viária. Em caráter preliminar é indicada uma nova especificação para a escolha de materiais para revestimento primário, atendendo às peculiaridades dos materiais tropicais. / County roads represent an important share of the total extension of the road network in Rio Grande do Sul, one of the Brazilian states. In most municipalities, the activities of these roads take a significant part of their budgets. Even so, the management strategies used are deficient, either from a technological development perspective or from the administrative controls and costs viewpoint. In this work the bases of a management system are proposed, adapted to the reality of the county roads found in the municipalities studied. The main feature of the system is the rationalization of the maintenance, improvement and construction activities, assuring a better use of the available resources and a progressive improvement of the road network. A new specification for the materials for unpaved roads is presented in a preliminary sense, based on the peculiarities of the materials usually found in tropical regions.

Thesis (MS)--University of Montana, 2009. / Contents viewed on December 21, 2009. Title from author supplied metadata. Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 136-139). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 136-139). Also available on the Internet.

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