Thesis. 1979. M.Arch--Massachusetts Institute of Technology. Dept. of Architecture. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Includes bibliographical references. / M.Arch

The subject of this study is rainfall-runoff forecasting and flood warning. Denote by (X(t),Y(t)) a sequence of equally spaced bivariate random variables representing rainfall and runoff, respectively. A flood is said to occur at time period (n + 1) if Y(n + 1) > T where T is a fixed number. The main task of flood warning is that of deciding whether or not to issue a flood alarm for the time period n + 1 on the basis of the past observations of rainfall and runoff up to and including time n. With each decision, warning or no warning, there is a certain probability of an error (false alarm or no alarm). Using notions from classical decision theory, the optimal solution is the decision that minimizes Bayes risk. In Chapter 1 a more precise definition of flood warning will be given. A critical review (Chapter 2) of classical methods for forecasting used in hydrology reveals that these methods are not adequate for flood warning and similar types of decision problems unless certain Gaussian assumptions are satisfied. The purpose of this study is to investigate the application of a nonparametric technique referred to as the k-nearest neighbor (k-NN) methods to flood warning and least squares forecasting. The motivation of this method stems from recent results in statistics which extends nonparametric methods for inferring regression functions in a time series setting. Assuming that the rainfall-runoff process can be cast in the framework of Markov processes then, with some additional assumptions, the k-NN technique will provide estimates that converge with an optimal rate to the correct decision function. With this in mind, and assuming that our assumptions are valid, then we can claim that this method will, as the historical record grows, provide the best possible estimate in the sense that no other method can do better. A detailed description of the k-NN estmator is provided along with a scheme for calibration. In the final chapters, the forecasts of this new method are compared with the forecasts of several other methods commonly used in hydrology, on both real and simulated data.

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This thesis reports the use of a time-series analysis approach to study the catchment hydrological system of the River Ribble. Rain gauge records, radar rainfall estimates and flow data are used in the analysis. The preliminary study consists of the flow forecasting at Reedyford, Pendle Water (82 km2). Flow forecasts generated from the rain gauge records are better than the radar rainfall estimates over this small catchment. However, the catchment response to rainfall is quick and no clear advantages in extending the lead-time of the forecast can be introduced by using an artificial time delayed rainfall input. A non-linear rainfall-flow relationship has been studied using the rain gauge rainfall and flow records at the River Hodder catchment (261 km2). A calibration scheme is used to identify the non-linear function of the catchment as well as the rainfall-flow system model. Although a better time-invariant system model can be identified, the non-linear rainfall-flow process cannot be fully explained by a power law function of effective rainfall. Assuming the dynamic, nonlinear system characteristics of the catchment can be reflected by a time-varying model gain parameter, relationships between the parameter and the flow, and between the parameter and the rainfall can be evaluated. These relationships have been used to improve the flow forecast during storm events. The results indicate, however, that the approach failed to improve the flow forecast near the peak flow condition. Radar data have been incorporated to forecast the flow at Jumbles Rock (1053 km2) and Samlesbury (1140 km2), River Ribble. The radar data calibrated by the Lancaster University Adaptive Radar Calibration System appears to produce better flow forecasts than the standard radar data product calibrated by the Meteorological Office. The proposed flow forecasting scheme generates better forecasts than the current system operated by the National Rivers Authority, North West Region.

This study examines fruit predation of species in the family Dipterocarpaceae. It was conducted in Pasoh Forest Reserve, a Lowland Dipterocarp Rain Forest in West Malaysia. The work concentrates upon the pre-dispersal weevil predators, whose larvae develop within dipterocarp fruit. After describing the pre-dispersal predators the host specificity of their larvae is examined. A comparison of host records determined in this study with records in the literature demonstrates statistically significant generic specialization by the larvae of some weevil species. The larvae of other species are also restricted to hosts within one genus, but sampling effort was insufficient to demonstrate generic specialization. The most abundant pre-dispersal weevil predator was <i>Nanophyes shoreae</i>. Aspects of the biology of this species are described. These include: the activity of the adult weevils during dipterocarp flowering events; the timing of oviposition; the length of the pre-imaginal development period; the survivorship of adult beetles kept under laboratory conditions. The period of pre-imaginal development varied between host species but was consistent between trees of one species. Quantitative analyses of <i>Nanophyes shoreae's</i> pre-imaginal mortality are also described. The primary mortality factors were abortion of fruit containing eggs and consumption of pupae and III instar larvae by vertebrates. Adaptations that may reduce losses to these primary mortality factors are considered. They include oviposition within those fruit that are least likely to abort and variability in the length of the pre-imaginal development period, causing synchronous development in larvae developing from eggs that were deposited on different dates. None of the dipterocarp fruit predators could be located during periods when dipterocarp fruit were not available. Analyses of their population recruitment during fruiting events and of the availability of fruiting trees (as determined by a phenological survey of Pasoh Forest Reserve) indicates that they are unlikely to have dispersed widely in search of fruiting dipterocarps. The existence of an alternative larval or adult host is discussed.

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Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1979. / Bibliography: leaves 87-93. / Microfiche. / xvi, 218 leaves ill., maps 29 cm