Hydrometeorological impact of urbanization in Metro Manila : Habagat 2013

Date of Award

2017

Document Type

Thesis

Degree Name

Master of Science in Atmospheric Science

Department

Physics

First Advisor

Narisma, Gemma Teresa T., Ph.D.

Abstract

The effects of urban expansion on local meteorology and hydrology of Metro Manila during an extreme rainfall event are assessed from the results of the Weather Research and Forecasting (WRF) and WRF-Hydro model simulations. The WRF model is used to simulate and downscale Habagat 2013, a four-day (18-21 August 2013) enhanced southwest monsoon event for two land cover scenarios. WRF-Hydro simulation is then performed to gain useful information about the hydrologic response of the area to the meteorological forcing and land cover setting prescribed. Land cover maps are derived from the 1972 and 2009 Landsat data to represent past and present urban scenarios. Lateral boundary conditions are interpolated from the National Centers for Environmental Prediction Final Operational Global Analysis data (NCEP FNL).Climatological characterization of multi-day extreme rainfall events in Metro Manila from 1961 to 2013 shows that Habagat 2013 is ranked third with quantile rank of 98.9 percentile. Changes in the land surface characteristics, associated with the conversion of cropland to urban, increased rainfall on the average by about 12%. Urbanization impacts in the energy balance is due to the increase in roughness length and decrease in albedo. These changes increased sensible and ground heat flux by 34% and 45%, respectively. In contrast, latent heat flux decreased by 48%. Results of the WRF-Hydro simulation show decrease in evaporation and soil moisture by 71% and 0.11%, respectively. Runoff consequently increased by 26% after urban expansion as a result of the increase in rainfall. This increase in runoff caused a corresponding increase in the streamflow peak in the study area.

Comments

The A7.G67 2017

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