Adaptive Response of Flood Mitigation in Dynamic Change of Land Use

Savitri, Yang Ratri (2021) Adaptive Response of Flood Mitigation in Dynamic Change of Land Use. Doctoral thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Flood is one of the natural hazards that frequently occurs in Indonesia, and it mainly occurs in major cities with significant numbers of population. It is commonly known that people prefer to live in urban areas to have better opportunities. As a result, this condition increases the number of population, and affects the land-use changes. Further, it decreases the open land and green open space as these areas consequently changed into developed areas. According to the hydrology cycles, the land-use changes can increase the surface runoff and provoke inundation problems affecting the losses, such as casualties, social, and economic losses. Additionally, it impacts the development of a city. Therefore, controling the inundation problems as one of mitigation measures is very necessary and essential. One of the mitigation measures that can be used to decision-making is flood risk assessment. This research conducts flood risk assessments based on semiquantitative and quantitative methods. The semi-quantitative method is used to obtain the weight parameters, and to present the priority areas. Meanwhile, the quantitative method quantifies the damage losses due to floods based on risk curve analysis. The obtained weight parameter is based on semi quantitative method, and is used to generate the score to determine the vulnerable drainage system in Surabaya. Further, the most vulnerable drainage system is divided into several areas to determine the areas or districts based on the rank of priority. Several variables are considered to determine the vulnerable areas consisting of flood hazards, social economy, and environmental. The flood hazard is represented by the inundation characteristic, whereas the population within an area is represented by the social variables. The land-use types represent the economic variables, meanwhile the environment describes the area's situation. The weight parameter obtained from the semi-quantitative analysis shows that flood hazard has a significant influence and reaches out the priority vector approximately 51%. Other than that, population and land use types also contribute to the affected areas, which become more vulnerable. It is shown from the obtained social and economic variables that the priority vector is up to 27%. Meanwhile, the environmental variables delivers less contribution in generating the vulnerable areas, with the obtained score approximately 22%. The vulnerable drainage system is generated by implementing this weight parameter based on the analytical hierarchy process (AHP) structures. The result shows that the Kedurus primary channel is the most vulnerable drainage system compared to others. It achieved a score of approximately 0.59. The selected drainage system is used to conduct a further risk assessment using a quantitative method by considering the flood characteristics. The flood characteristics are generated from flood simulation for future scenarios. The parameters used to build future scenarios are obtained from the sensitivity analysis and validation model. Several boundary conditions consisting of flow hydrograph, normal depth, stage hydrograph, and rain on-grid are being tested to obtain the suitable result that represents the actual condition. The suitable result is evaluated based on RMSE values by comparing the model to historical data. The result shows that the combination of flow hydrograph as the upstream boundary condition and stage hydrograph as the downstream boundary condition is approximate to the actual condition with The RMSE value obtained 0.206, which is less than other scenarios. Further, the future simulation considers the storage areas as one of the measures proposed by the master plan. The future scenarios are built by simulating the availability of storage areas to control the flooding that occurs. The simulation shows that the storage areas can decrease the surface runoff that flows into the channels. However, it is difficult to assess the effectiveness of storage areas merely from flood characteristics. Therefore, the quantitative method is used to quantify the damage losses based on the flood risk curve. The flood risk curve is generated based on three variables, namely hazards, vulnerability, and exposure. The hazard variables are obtained from flood modeling based on several return periods consist of 2 years, 5 years, 10 years, 25 years, and 50 years. The vulnerability variables perform the depth-damage function of damage value by the range 0 to 1. The exposure generates the total areas of each land use type as the areas exposed by the inundation. Each of the land use types is associated with economic value. Furthermore, the combination of these three variables resulted the flood risk curve which represent the total consequences caused by the inundation. This flood risk curve is implemented to the most vulnerable drainage system, which is previously determined. The total consequences is calculated based on two conditions, without mitigation and with mitigation. According to the flood risk curve, it shows that the damage losses without mitigation based on existing land use is $ 3.176.246, whilst the optimization of storage capacity obtain the damage losses $ 2.587.195. It indicates that the benefit is approximate to $ 589.051. Moreover, the damage losses without mitigation based on future land use planning is $ 3.537.081. Meanwhile, the consideration of storage areas based on future planning obtain the damage losses $ 2.951.250. It represents the benefit, which is approximately $ 585.831. keywords: flood, hazards, inundation, land use, risk, vulnerability.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: flood, hazards, inundation, land use, risk, vulnerability banjir, hazards, genangan, tata guna lahan, resiko, kerentanan
Subjects: H Social Sciences > HT Communities. Classes. Races > HT133 City and Towns. Land use,urban
T Technology > TC Hydraulic engineering. Ocean engineering > TC530 Flood control
Divisions: Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Civil Engineering > 22001-(S3) PhD Thesis
Depositing User: Yang Ratri Savitri
Date Deposited: 18 Aug 2021 08:29
Last Modified: 18 Aug 2021 08:29
URI: https://repository.its.ac.id/id/eprint/88081

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