Estimasi Model Hidrolika Menggunakan HEC-RAS 1-D dan Tren Prediksi Strategi Mitigasi Banjir

Engineering modeling is becoming a trend and important because it can simulate a variety of decision scenarios to be applied in the field. With limited facilities and technology, 1-D modeling in hydraulics for flood mitigation is still a trend today. What are the weaknesses of this model and how is the prediction of future modeling trends? This study analyzes the flood modeling of the Tuntang River with the 1-D model using HEC-RAS to analyze the condition of the existing water level profile and flood mitigation scenarios with normalization. The results of the analysis show that the 1-D model can describe conditions in the field and scenarios clearly. However, the 1-D model has limitations because it cannot carry out simulations that consider aspects of construction costs, time, and budget allocation of stakeholders to determine the priority scale of disaster-affected areas. It requires a vulnerability analysis with field observations, 2-D or 3-D modeling, and the application of value engineering to optimize flood control strategies. With the advancement of technology, this trend is predicted to be something that will be done in the future.

Mitigasi Dan Adaptasi Bencana Banjir di Kecamatan Pallangga Kabupaten Gowa

Bencana banjir yang terjadi secara terus-menerus dapat menyebabkan berbagai kondisi yang apabila terjadi dapat menimbulkan berbagai kerentanan yang memerlukan pemikiran yang lebih dalam untuk mengantisipasi bencana banjir. Mitigasi dan Adaptasi Bencana Banjir di Kecamatan Pallangga Kabupaten Gowa bertujuan untuk memetakan tingkat kerentanan bencana banjir dan upaya mitigasi dan adaptasi yang tepat berdasarakan tingkat kerentanan bencana banjir di Kecamatan Pallangga. Sejalan dengan tujuan penelitian ini maka dalam penelitian ini menggunakan metode penelitian deskriptif kualitatif, untuk menentukan tingkat kerentanan dengan analisis spasial overlay dan skoring parameter penentu kerentanan banjir. Hasil dari penelitian ini adalah Kecamatan Pallangga diklasifikasi dalam tiga tingkat kerentanan bencana banjir meliputi rentan tinggi, rentan sedang dan rentan rendah serta arahan mitigasi dan adaptasi bencana banjir berdasarkan tingkat kerentanan. The floods disasters that occur continuously can cause various conditions which can cause a variety of vulnerabilities that require deeper thought to anticipate. Flood mitigation and adaptation in Pallangga District of Gowa aims to map the level of flood vulnerability and provide mitigation and adaptation directions based on the level of flood vulnerability in Pallangga. This research uses descriptive qualitative research methods, to determine the level of vulnerability with spatial overlay analysis and weight scoring of parameters determining flood vulnerability. The results of this research are in Pallangga classified into three levels of vulnerability to flood disasters including high vulnerability, medium vulnerability and low vulnerability with directives flood mitigation and adaptation based on the level of vulnerability.

Reduce Flood Losses Of Kali Tanggul Using Spatial Based Technical Approaches

Flood disasters frequently occurred in Jember Regency, East Java. It is usually caused by the overflow of the Tanggul River in the rainy season, especially in the downstream area. Flood control could be done by building dams, embankments, shortcuts, and other technical flood protections. Meanwhile, mitigation efforts such as developing thematic maps of flood inundation need to be done to minimize losses caused by the flood. This study aims to design a flood mitigation strategy technically. The flood control structure was proposed by designing a shortcut in Kali Tanggul. Its performance was analyzed to reduce flood inundation in the Tanggul watershed. The flood inundation modeling was carried out using spatial analysis using ArcGIS 10.1 and hydraulic analysis using HECRAS 5.0.3. Flood inundation results were compared with the Tanggul watershed flood map developed by UPT PUSDA Lumajang. Based on modeling results, flood control using shortcuts is considered an effective strategy for flood mitigation. It was indicated by the reduction of flood inundation distributions, flood inundation height, and flood-affected areas. The results show that the flood height decrease 0.47 up to 0.56 m

Ecosystem Service Modelling to Support Nature-Based Flood Water Management in the Vietnamese Mekong River Delta

Deltas are among the most productive and diverse global ecosystems. However, these regions are highly vulnerable to natural disasters and climate change. Nature-based solutions (Nbs) have been increasingly adopted in many deltas to improve their resilience. Among decision support tools, assessment of ecosystem services (ES) through spatially explicit modelling plays an important role in advocating for Nbs. This study explores the use of the Land Utilisation and Capability Indicator (LUCI) model, a high-resolution model originally developed in temperate hill country regions, to map changes in multiple ecosystem services (ES), along with their synergies and trade-offs, between 2010 and 2018 in the Vietnamese Mekong Delta (VMD). In so doing, this study contributes to the current knowledge in at least two aspects: high-resolution ES modelling in the VMD, and the combination of ES biophysical and economic values within the VMD to support Nbs implementation. To date, this is the highest resolution (5 by 5 m) ES modelling study ever conducted in the VMD, with ~1500 million elements generated per ES. In the process of trialling implementations of LUCI within the VMD’s unique environmental conditions and data contexts, we identify and suggest potential model enhancements to make the LUCI model more applicable to the VMD as well as other tropical deltaic regions. LUCI generated informative results in much of the VMD for the selected ES (flood mitigation, agriculture/aquaculture productivity, and climate regulation), but challenges arose around its application to a new agro-hydrological regime. To address these challenges, parameterising LUCI and reconceptualising some of the model’s mechanisms to specifically account for the productivity and flood mitigation capability of water-tolerant crops as well as flooding processes of deltaic regions will improve future ES modelling in tropical deltaic areas. The ES maps showed the spatial heterogeneity of ES across the VMD. Next, to at least somewhat account for the economic drivers which need to be considered alongside biophysical valuations for practical implementations of ES maps for nature-based solutions (Nbs) in the upstream VMD, economic values were assigned to different parcels using a benefit transfer approach. The spatially explicit ES economic value maps can inform the design of financing incentives for Nbs. The results and related work can be used to support the establishment of Nbs that ultimately contribute to the security of local farmers’ livelihoods and the sustainability of the VMD.

Understanding the effect of changing land use on floods and soil erosion in the Cagayan de Oro catchment

<p>The destructive capability of typhoons affects lives and infrastructure around the world. Spatial analysis of historical typhoon records reveal an area of intense storm activity within the Southeast Asian (SEA) region. Within SEA is the Philippines, an archipelagic tropical country regularly struck by storms that often cause severe landslides, erosion and floods. Annually, ˜20 cyclones enter the Philippine Area of Responsibility, with about nine making landfall, causing high winds and intense rainfall. Thus, significant research in the Philippines has focused on increasing the resilience of ecosystems and communities through real-time disaster forecasting, structural protections, and programmes for sustainable watershed management (e.g. rehabilitation and conservation agriculture). This dissertation focused on the third aspect through computer modelling and scenario analysis. The study area is the Cagayan de Oro (CDO) catchment (˜1400km²) located in the Southern Philippines. The catchment experienced heavy flooding in 2012 from Typhoon Bopha and has major erosion problems due to mountainous slopes and heavy rainfall. Communities derive ecosystem services (ES) including agricultural production, water supply, recreation, mining resources, flood mitigation, etc. Since changes to the supply or distribution of these ES affects livelihoods and the hydrological response of the catchment to typhoon events, this research used the Land Utilisation and Capability Indicator (LUCI) model to understand the baseline ES and potential changes associated with basin management plans. This was the first detailed tropical application of LUCI, including parameterising it for Philippine soil and land cover datasets in CDO and extending its capability to be applied in future tropical areas. Aside from applying LUCI in a new geoclimatic region, this research contributed to the general development of LUCI through testing and improving its sediment delivery and inundation modelling. The sediment delivery was enhanced using the Revised Universal Soil Loss Equation (RUSLE) model that allows LUCI for the first time to account for impacts of specific land management such as agroforestry and contour cropping on erosion and sediment delivery. Progress was made in updating a flatwater inundation model for use with LUCI, including converting it to Python but this requires further development and testing before it is suitable for application in the Philippines. The development and rehabilitation scenarios showed improved flood mitigation, lower surficial soil erosion rates, and lower loads of nutrients compared to the baseline scenario. Additionally, ES mapping under different land cover scenarios has not been previously accomplished in CDO, and this research provides useful information to guide local decision-making and management planning. The rainfall-runoff model of LUCI was tested against the Hydrologic Engineering Center’s Hydrological Modelling System (HEC-HMS), showing good agreement with observed flow. Since the rainfall-runoff model of LUCI has been minimally utilised in past applications, this CDO application elucidated directions for future work around further testing under extreme rainfall events and climate change. Overall, this novel application of LUCI creates a framework to assist decision-making around land cover changes in the CDO, provides guidance around data requirements and parameterisation procedures to guide future international applications, and has significantly contributed to development and improvement of the LUCI framework to extend its modelling capabilities in the future.</p>

Understanding the effect of changing land use on floods and soil erosion in the Cagayan de Oro catchment

<p>The destructive capability of typhoons affects lives and infrastructure around the world. Spatial analysis of historical typhoon records reveal an area of intense storm activity within the Southeast Asian (SEA) region. Within SEA is the Philippines, an archipelagic tropical country regularly struck by storms that often cause severe landslides, erosion and floods. Annually, ˜20 cyclones enter the Philippine Area of Responsibility, with about nine making landfall, causing high winds and intense rainfall. Thus, significant research in the Philippines has focused on increasing the resilience of ecosystems and communities through real-time disaster forecasting, structural protections, and programmes for sustainable watershed management (e.g. rehabilitation and conservation agriculture). This dissertation focused on the third aspect through computer modelling and scenario analysis. The study area is the Cagayan de Oro (CDO) catchment (˜1400km²) located in the Southern Philippines. The catchment experienced heavy flooding in 2012 from Typhoon Bopha and has major erosion problems due to mountainous slopes and heavy rainfall. Communities derive ecosystem services (ES) including agricultural production, water supply, recreation, mining resources, flood mitigation, etc. Since changes to the supply or distribution of these ES affects livelihoods and the hydrological response of the catchment to typhoon events, this research used the Land Utilisation and Capability Indicator (LUCI) model to understand the baseline ES and potential changes associated with basin management plans. This was the first detailed tropical application of LUCI, including parameterising it for Philippine soil and land cover datasets in CDO and extending its capability to be applied in future tropical areas. Aside from applying LUCI in a new geoclimatic region, this research contributed to the general development of LUCI through testing and improving its sediment delivery and inundation modelling. The sediment delivery was enhanced using the Revised Universal Soil Loss Equation (RUSLE) model that allows LUCI for the first time to account for impacts of specific land management such as agroforestry and contour cropping on erosion and sediment delivery. Progress was made in updating a flatwater inundation model for use with LUCI, including converting it to Python but this requires further development and testing before it is suitable for application in the Philippines. The development and rehabilitation scenarios showed improved flood mitigation, lower surficial soil erosion rates, and lower loads of nutrients compared to the baseline scenario. Additionally, ES mapping under different land cover scenarios has not been previously accomplished in CDO, and this research provides useful information to guide local decision-making and management planning. The rainfall-runoff model of LUCI was tested against the Hydrologic Engineering Center’s Hydrological Modelling System (HEC-HMS), showing good agreement with observed flow. Since the rainfall-runoff model of LUCI has been minimally utilised in past applications, this CDO application elucidated directions for future work around further testing under extreme rainfall events and climate change. Overall, this novel application of LUCI creates a framework to assist decision-making around land cover changes in the CDO, provides guidance around data requirements and parameterisation procedures to guide future international applications, and has significantly contributed to development and improvement of the LUCI framework to extend its modelling capabilities in the future.</p>