n Journal of Emerging Trends in Engineering and Applied Sciences - Three-input transfer function modeling of rainfall in Calabar, Cross River State of Nigeria

Volume 4, Issue 4
  • ISSN : 2141-7016
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The city of Calabar is affected by regular flooding due to heavy rainfall and urbanization. Government has attempted to control flooding by building drainages. However, this has not kept pace with land use due to paucity of funds. Presently, Calabar has poor rain forecast mechanism as it depends on very short term forecast notice from the Calabar airport metrological station and hence does not provide long term advance rain and flood warnings. Therefore, there is need to investigate and develop accurate rain forecasting and flood warning mechanism for Calabar. This is the motivation for this study. In this paper, we developed an empirical model to forecast rainfall in Calabar using a three-input transfer function (TF) modeling technique. We obtained historical data on rainfall, relative humidity, sunshine, temperature difference and cloud cover for the period 1996-2007 from the National Metrological Center, Oshodi-Nigeria. However, significant association with rainfall was established for relative humidity, cloud cover and temperature difference. Hence, sunshine was dropped as a possible predictor. Using impulse response functions, four TF models were identified of which the TF (3, 2, 2, 2) model, which predicted rainfall with a root mean square percentage error of 2.3%, was adopted as the most appropriate model. The model also performed better than both multiple regression and univariate SARIMA (1, 0, 1)*(1, 0, 1) models. If adopted by the Calabar Municipal Council, the model has the potential of helping the council to develop an annual rain forecasting and water management plan that will impact positively on flood and erosion control. The model is developed for the Calabar city and would require further testing before adoption by cities within the same geographical location with Calabar.

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