Date of Publication

12-2022

Document Type

Bachelor's Thesis

Degree Name

Bachelor of Science in Civil Engineering with Spec in Hydraulics and Water Resources Engg

Subject Categories

Civil Engineering | Engineering

College

Gokongwei College of Engineering

Department/Unit

Civil Engineering

Thesis Advisor

Renan Ma. T. Tanhueco

Defense Panel Chair

Mario P. De Leon

Defense Panel Member

Lessandro Estelito O. Garciano

Abstract/Summary

Due to the high susceptibility of flooding within Pasig City brought by the Pasig Marikina River (PMR), structural and non-structural measures were undertaken by the local government as a means for flood mitigation and management. Key projects under the structural measures include the construction of Manggahan Floodway, Rosario Weir and Napindan Hydraulic Control Structure (NHCS). The Rosario Weir was built at the confluence of PMR and the Manggahan Floodway, whereas the NHCS was built at the confluence of PMR and Napindan Channel. Both the Manggahan Floodway and Napindan Channel divert river discharge from the PMR to Laguna Bay via Rosario Weir and NHCS, respectively. Studies show that the operation of these flood control structures, i.e. the Rosario Weir and NHCS, play a significant role in flood water management. However, these flood control structures collectively performed poorly in 2009 resulting in an increase in flooded areas in the aftermath of Typhoon Ondoy. In line with this, it was found that there is limited documentation on the operations of these flood control structures with respect to its implications on the flow and flooding behavior along PMR. Therefore, this study developed a model using the river analysis tool, Hydrological Engineering Centre – River Analysis System (HEC-RAS), in order to understand the interaction of the flooding behavior along the lower Marikina River with respect to the operation rules of the flood control structures during Typhoon Ulysses. The flooding behavior was measured in terms of flow, water level, and timing of channel flow. In real practice, the Metro Manila Development Authority - Effective Flood Control Operation System (MMDA-EFCOS) base the gate controls of these flood control structures at the Sto. Niño water level gauge station, located farther upstream from the Rosario weir. However, HEC-RAS only allows for gate operations to be referenced at the water levels immediately upstream of the weir. Hence, two models were developed in HEC-RAS with different approaches in gate rules: the first (Approach 1) assumes that the MMDA-EFCOS gate operations are based immediately upstream of the gates, and the second (Approach 2) uses the calibrated rules of operation from the first approach by taking the correlation of water surface elevations between Sto. Niño and Rosario weir. Results of the simulation was validated based on applicable model performance indicators and the analysis of flooding behavior along the lower Marikina river. Results show that both approaches yielded very good performance ratings, which depict that the simulated flows and water levels are a very good likeness of the observed data. However, Approach 2 yielded slightly better results than Approach 1. On the other hand, in the analysis of flooding behavior along the lower Marikina river, it was observed that the rules applied in Approach 1 resulted in water being piled up at Rosario weir before and after peak flow, which led to the sudden great influx of water along the lower Marikina river. This was attributed to the fact that since Approach 1 assumes the MMDA-EFCOS gate operations to be based immediately upstream of the gates, the flood arrival time between Sto. Niño and Rosario is shorter, which resulted in the delay in floodgate operations and water being piled up before and after peak flow. Overall, results of the study show that the developed model performs well in simulating the flow along PMR. The comparison of results between Approach 1 and Approach 2 proves that the operation of the flood control structures plays a significant role in flood water management, since in Approach 2, the calibrated rules of operation significantly reduced the amount of water being piled up at Rosario before and after peak flow, as well as the sudden great influx of water along the lower Marikina river during these times in the simulation.

Abstract Format

html

Language

English

Format

Electronic

Keywords

Flood forecasting—Philippines; Flood control—Philippines; Hydraulic structures—Philippines

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Embargo Period

12-24-2022

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