Perception of flood hazard and adjustment in Brisbane

Abstract

nnnnn This thesis examines factors which influence Brisbane flood plain occupants' perception and evaluation of the flood hazard. It also looks at their evaluation of the effectiveness of public and private adjustments and the variables affecting their adoption decision. nnnnn As the basis for analysis, three hypotheses are set up. Hypothesis 1 relates to the factors associated with variations in hazard perception and evaluation, those under consideration being perceived frequency and magnitude of the natural event, knowledge and experience of the flood hazard and expectation of future flooding. The second hypothesis pertains to the choice of adjustment, stating that this is a function of evaluation of the hazard, awareness of the choices open and evaluation of alternatives. In the third, it is hypothesized that there exist rational explanations for the persistence of human occupance in hazard areas. nnnnn Information obtained from a personally administered questionnaire forms the main data base. The sample v.-as selected by a systematic technique in which every tenth residential unit which had experienced some degree of flooding in January, 1974 is included. In all, 647 interviews were obtained from either the household head or spouse. The bulk of statistical analysis is carried out using packaged computer programmes, crosstabulation and chi-squared being the main methods used. Basically, findings suggest the hypotheses may be accepted as stated, though some refinement can be made regarding the characteristics of the variables involved. In the first hypothesis, hazard evaluation varies directly with expected flood frequency. However, it appears that responses can more appropriately be classified in terms of certainty and uncertainty. While hazard evaluation varies directly with height of flood waters in the dwelling, a more important distinction exists between those who experienced flooding in their dwelling and those who did not. Both recency and amount of personal experience, knowledge of previous floods, and expectation of future flooding are also significantly related to hazard evaluation. nnnnn In examining the second hypothesis, again relationships appear more complex than originally anticipated. Significant relationships are established between the adoption of private adjustments and a number of factors including perceived frequency and magnitude of flooding, future flood expectation, hazard evaluation and experience. Perception of public adjustments is significantly related to the first three, but not to the last two. nnnnn While the overall range of public adjustments perceived is relatively broad, individual respondents knowledge is more restricted. Information, warning and evacuation measures are generally given the highest ranking by respondents, followed by zoning regulations. In the main, technical adjustments are ranked below these in effectiveness. However, they are the government action most frequently sought. nnnnn Amount of experience and adoption of adjustments at the time of the flood are significantly related. Little difference exists in the type of adjustment adopted since the flood, suggesting a common pool of knowledge has developed. Few occupants have adopted major adjustments. Most appear to place their reliance on last minute emergency measures for protection. Relocation is a favoured alternative but often precluded from consideration by economic and social constraints. The situation of increased public confidence being generated by a knowledge of public mitigation work does not appear to be operative in the present study. nnnnn In the final analysis, one factor, information, stands out for its role in both perception of the hazard and response to it. Its direct role in the adoption decision appears to be of particular importance. As an adjustment, the provision of information is the one most sought and also appears to have the most potential in influencing the adoption of other adjustments. nnnnn On the basis of these observations, three planning proposals are made. These are: (1) the extension of information provision (2) the improvement of flood forecasting, warning services and evacuation plans, and (3) the development of positive preventive measures such as zoning regulations to induce development away from the flood plain. nnnnn Finally, three avenues for future research are proposed including the examination of the information and warning component of hazard perception and the adoption decision, a study through time of one community to gauge the effect of information flows and third, benefit-cost analysis at the level of the individual flood plain occupant.