Structural Flood Mitigation Research Articles

Assessing flood susceptibility and effectiveness of structural flood mitigation measures applied within Mubuku catchment in Rwenzori Region, Uganda

Assessing flood susceptibility and effectiveness of structural flood mitigation measures applied within Mubuku catchment in Rwenzori Region, Uganda

To What Extent Have Nature-Based Solutions Mitigated Flood Loss at a Regional Scale in the Philadelphia Metropolitan Area?

Globally, floods are becoming more severe, lasting longer, and occurring more frequently because of changes in climate, rapid urbanization, and changing human demographics. Although traditional structural flood mitigation infrastructures (e.g., drainage systems, levees) are effective in urban areas, their functionalities in the face of extreme rainfall events and increased development largely depend on the capacity and location of such systems, making complementary solutions such as nature-based solutions (NBS) important. The concept of NBS within the context of flood mitigation has gained traction in the last decade; however, the success of NBS depends on their effectiveness and distribution over urban regions. This article seeks to examine the potential of NBS as a flood loss mitigation tool in one of the fastest-growing and flood-prone counties of Pennsylvania, Montgomery County, using Generalized Linear Model (GLR) and Geographically Weighted Regression (GWR) techniques. The analysis integrates the National Risk Index dataset for river flooding, a 100-year flood zone layer from National Flood Hazard Layer (NFHL) provided by FEMA, with land use and impervious surface percent data derived from National Land Cover Database (NLCD) for 2019 and socioeconomic data at the U.S. census tract level from the 2019 U.S. Census. This study’s findings partially contradict previous research by revealing an unexpected relationship between NBS quantity in floodplains and expected annual loss. Findings also suggest that small size and disconnected patches of NBS in floodplains in some dense urban areas effectively reduce total losses from flood events.

Flood Frequency Analysis of Lower Krishna Basin using Gumbel Method at Prakasam Barrage, Vijayawada, Andhra Pradesh

The Gumbel Distribution approach is used in this study for analyzing the flood frequency in the lower Krishna basin. It is a probability distribution method that was used to predict river annual peak discharges from 2007 through 2021 (14 years). The probability distribution function was used to calculate the return period for 2, 5, 10, 15 and 20 years and estimated discharges were produced. The flood for the next 10 years will be 1239523 Cusecs and the predicted flood discharge for the next 25 years will be 1586634 Cusecs. The expected flood from 2 to 25 years has also indicated a consistent growing tendency in selected Prakasam barrage station. This type of information would be useful in the planning of engineering projects such as reservoirs, bridges, flood mitigation structures etc. Flood hazard maps can also be created using these methodologies.

Effectiveness of Strategically Located Green Stormwater Infrastructure Networks for Adaptive Flood Mitigation in a Context of Climate Change

Studies indicate Green Stormwater Infrastructure (GSI) on industrial land can provide substantial adaptive flood mitigation within urban catchments under climate change. To identify a cost-effective adaptive GSI network, planners need to evaluate flood mitigation capabilities of industrial properties through time and understand key characteristics informing when, where, and how GSI should be implemented for maximum effect. We applied the Hydrology-based Land Capability Assessment and Classification (HLCA+C) methodology to a catchment in Christchurch, New Zealand, to evaluate the capabilities of industrial properties clustered into Storm Water Management (SWM) zones under different climate change scenarios. SWM zone potentials and limitations were assessed to develop the most capable adaptive flood mitigation network with climate change. We prioritised six of twenty SWM zones for inclusion in the network based on their substantial flood mitigation capabilities. To maximise their capabilities through time, we orchestrated, and implemented GSI in zones incrementally, using different implementation approaches based on key characteristics determining their capability. The results indicated that the most capable zone could mitigate climate change-induced flooding, by itself, up to the end of this century under the moderate climate change scenario. However, if its capability was combined with that of five others, together they could mitigate flooding just shy of that associated with the major climate change scenario up to the end of this century. The resulting adaptive industrial GSI network not only provides substantial flood protection for communities but allows costly investments in flood mitigation structures, such as barriers and levees, to be safely delayed until their cost-effectiveness has been confirmed under increased climate certainty.

The impacts of flood-mitigation structures on floodplain ecosystems: a review of three case studies from Australia and France

ABSTRACT This study is concerned with the physical impacts of flood-mitigation structures on ‘humanised’ and ‘natural’ floodplain ecosystems. The former constitute fertile, well drained and developed surfaces. The latter are mainly degraded wetland areas located in the backwater zones of wide, low-lying floodplains. Three rivers are investigated: the Hawkesbury–Nepean and the Macleay Rivers in New South Wales, Australia and the Durance River in southern France. Their floodplains, flood-mitigation works and floodplain ecosystems are analysed, together with site- and time-dependent differences in their floodplains, their exploitation and their degradation. Conservation of floodplains seeks to reverse wetland degradation, and to increase biodiversity and sustainability, as well as preserving developed floodplains. This study discusses gaps in our biophysical knowledge of ecosystems and the absence of ecological indicators of degradation. It also considers the lack of data on socio-economic values for what are unique, site- and time-specific, biophysical systems. Only when such inadequacies are addressed will the values of ecosystems be fully understood. Then cost-effective management might be possible. These knowledge gaps contribute to the many problems of floodplain management, which are likely to increase when the additional impacts of population increase and global warming become apparent.

Bivariate Flood Frequency Analysis: A case study of Rib River, Upper Blue Nile Basin, Ethiopia

Hydrological design, planning and design of flood mitigation structures require detailed knowledge of the characteristics of the flood event, i.e. peaks, volumes, occurrence times and duration. In addition to the uncertainty associated with the occurrence in both space and time, these events may often have a correlation of varying strengths. The literature study interestingly reveals that the majority of studies are based on a univariate approach rather than a more realistic approach that recognizes the multivariate nature of the underlying phenomenology. Therefore, the main objective of this study is to revisit the topic of sizing of flood events in terms of their frequency of occurrence using the ‘Copula’ based bivariate approach to analyze the joint distributions of correlated flood variables with a special focus on Ribb sub basin, Upper Blue Nile (Ethiopia) as the case study. The methodology was applied to flood attributes, i.e. flood peaks and volume generation from partial duration series (PDS) by applying run theory. The Joint Cumulative Distribution Function, the Conditional Cumulative Distribution Function and the associated Return Periods can be easily achieved based on the bivariate distribution of the copula and compared to the univariate analysis.

Geophysical and Societal Dimensions of Floods in Manitoba, Canada: A Social Vulnerability Assessment of the Rural Municipality of St. Andrews

Being strongly influenced by the landscape of the Red River Valley, geophysical and a variety of sociodemographic and economic factors, the characteristics of floods are complex in the Province of Manitoba, Canada, which causes substantial loss and damage to lives and properties. The primary objectives of this study are two-fold: (i) to identify the geophysical and human-induced conditions of floods, and examine the trend in flood loss and damage in the Province of Manitoba, Canada; and (ii) to analyze the social vulnerability perspectives of floods in the Rural Municipality of St. Andrews, as a local community case study. Using the Delphi technique, primary data were procured from the field for community-level vulnerability analysis. Secondary data for a provincial-level analysis were collected from various public domains, including governmental departments and other non-government sources. The results reveal that a nested set of geophysical and societal factors determine the degree of vulnerability of individual community members. In Manitoba, it was found that socioeconomic damages caused by floods have increased considerably over time despite undertaking costly structural flood mitigation measures. We conclude that minimization of flood damages requires complementing structural measures with knowledge-sharing, collaboration among pertinent institutions, and the adoption of an interactive flood management system approach.

Multicriteria analysis for identification of flood control mechanisms: Application to extreme events in cities of different Brazilian regions

The alteration of the land use of watersheds by urbanization generates changes in the hydrological response of a region. Urbanization brings improvements to the population's quality of life; however, the increase in impermeable surfaces, often without proper planning, has an impact on the environment. Impermeable surfaces decrease the infiltration of water and increase the runoff volume. Floods are common problems in cities with urban planning failures or accelerated population growth. In recent decades, municipalities have sought to invest in low-environmental-impact tools that control stormwater, such as best management practices (BMPs) and low-impact development (LID). To implement these tools, it is necessary to analyze the characteristics of each city, with the aim of selecting the best solution for flood control for that city. In this study, the main criteria considered in the decision-making process for the implementation of low-environmental-impact structural flood mitigation measures were identified as Control Mechanisms (CMs). Fuzzy logic was applied to five Brazilian cities with flood records to identify the most appropriate CMs for each city, based on the criteria analyzed. For the cities considered, the most adequate flood control mechanism, according to the criteria, was found to be the detention basin, with a minimum effectiveness of 0.892.

A Conflict between Traditional Flood Measures and Maintaining River Ecosystems? A Case Study Based upon the River Lærdal, Norway

Floods are among the most damaging of natural disasters, and flood events are expected to increase in magnitude and frequency with the effects of climate change and changes in land use. As a consequence, much focus has been placed on the engineering of structural flood mitigation measures in rivers. Traditional flood protection measures, such as levees and dredging of the river channel, threaten floodplains and river ecosystems, but during the last decade, sustainable reconciliation of freshwater ecosystems has increased. However, we still find many areas where these traditional measures are proposed, and it is challenging to find tools for evaluation of different measures and quantification of the possible impacts. In this paper, we focus on the river Lærdal in Norway to (i) present the dilemma between traditional flood measures and maintaining river ecosystems and (ii) quantify the efficiency and impact of different solutions based on 2D hydraulic models, remote sensing data, economics, and landscape metrics. Our results show that flood measures may be in serious conflict with environmental protection and legislation to preserve biodiversity and key nature types.

Improving Indian meteorological department method for 24- hourly rainfall downscaling to shorter durations for IDF modelling

The development of Intensity-Duration-Frequency (IDF) models for storm drain design and related flood mitigation structures requires rainfall amount and corresponding duration records. To achieve this purpose, three short duration downscaling methods from 24-hourly rainfall amount data were selected for improvement, namely: IMD, AIMD and MCIMD, with the CAMS method used as the experiment control. Three types of general PDF-IDF models (GEVT-1, LPT-3 and ND) were developed based on the downscaling methods yielding goodness of fit (R2) with very high correlation of 0.995–0.999 and model accuracy with mean square error (MSE) of 4.123–7.85. The PDF-IDF models predicted intensities plotted against durations for different return periods of 2, 5, 10, 25, 50 and 100 years, showed visual differences in the predictive performance of the intensities derived from the downscaling methods. Kruskal-Wallis non-parametric test of significance at 5% level carried out showed that no-significant difference exist for 15-60 minutes duration, while the difference was significant for durations between 90–300 minutes. The LPT-3 based on MCIMD yielded higher improved performance in prediction of intensities relative to the IMD. The level of improvement ranges from 35.17 to 52.26% and 25.0 to 39.89%; while that of AIMD ranges from 10.97 to 20.87% and 3.33 to 12.53% for 10 and 100 year return periods, respectively. The use of the IMD downscaling method with the LPT-3 PDF-IDF model for design purposes will be justified if modified with some percentage improvement or adjustment factor.

Entrapment of an estuarine fish associated with a coastal surge barrier can increase the risk of mass mortalities

Estuarine storm surge barriers are designed to prevent the flooding of human-developed landscapes. While such barriers may have a range of ecological impacts, including the fragmentation of aquatic habitats and the alteration of water quality, their impact on obligate estuarine fishes is largely unknown. The sparid, Acanthopagrus butcheri, was used as a model species to determine how surge barriers may influence the movements of solely estuarine species and fish kill events. Individual A. butcheri were monitored for one year using passive acoustic telemetry in the Vasse-Wonnerup Estuary (south-western Australia), in which fish kills occur regularly during summer and autumn. Hydrological data and surge barrier operational information were used to make inferences on the movements and habitat use of A. butcheri. Individuals were largely restricted to the waters downstream of the surge barriers. The fish tended to occupy deeper sites in proximity to complex structure with the distribution also influenced by changes in salinity during the spawning period. A strong seasonal trend existed in the daily distance travelled by the fish and this was positively associated with the annual flow period. The majority of fish that successfully passed upstream through one of the surge barriers did so through a fishgate that operated outside of the spawning period. All those fish were then likely trapped with no downstream fish passage occurring in summer and autumn at a time when water quality was characterised by low dissolved oxygen and cyanobacterial blooms. The surge barrier therefore acts as a seasonal trap and increases the risk of mass mortalities. Given a projected increased need to combat flooding and storm surges associated with climate change in low-lying coastal areas, the study highlights the necessity of ensuring that the life-cycles and movement requirements of estuarine fishes are considered in the design and operation of coastal flood mitigation structures.

Community perceptions of flood resilience as represented in cognitive maps

Community perceptions of flood resilience hinge upon translation of impressions of events and built environment, which thereby influence a community's ability to resist, cope with and recover from adverse impacts of flooding. Particularly in developing countries, NGOs, often in collaboration with communities, design and fund non‐traditional structural measures to enhance community resilience. This study examines community perceptions of flood resilience in the Haor region of Bangladesh, where communities live on constructed islands, reinforced by structural flood mitigation measures. Wave activity due to riverine flooding places communities at significant risk, especially as NGO‐funded non‐traditional structural measures intended to increase resilience may fail to do so. Small group meetings with community members were facilitated in graphically depicting and discussing areas of risk and relative safety during flood events. Maps constructed by community groups indicate that perceptions of community vulnerability are shared between generations, and that measures intended to enhance resilience may actually increase community perceptions of vulnerability, highlighting a need for a more nuanced understanding of community adaptation to ongoing risk. Findings identified the use of non‐language‐dependent tools such as cognitive mapping as quick and effective data collection mechanisms. Incorporating this local knowledge allows for more effective targeted measures, increasing community resilience and better informing NGO practices.

Challenges for flood risk management in flood‐prone Sirajganj region of Bangladesh

Although Bangladesh has suffered from different types of floods which have caused enormous damage to properties and lives, managing floods still remains a challenging task. Flood management is a multisectoral activity due to its complexity, scale, and multidisciplinary nature. Sirajganj district can be regarded as one of the most vulnerable areas in Bangladesh and hence a study was carried out for Sirajganj district to provide guidelines to combat challenges to flood risk management. The flood frequency analyses at three river stations using water level data were carried out, the flood inundation map for different return periods and a flood depth versus damage curve are plotted to address the vulnerable areas and damages, and to help design flood mitigation structures. It can be inferred that damages will be proportional to return period since the risk is a function of hazard, vulnerability, and exposure. Both structural and non‐structural measures including rejuvenation of the Jamuna River and low‐cost flood resistant building approaches for flood affected char (island) people are suggested along with a few recommendations to mitigate floods in the study area. The government, Non governmental organization (NGO), funding agencies, and transboundary countries should come forward to mitigate flood hazards to improve the livelihood of the affected people.

Comparison of Flood Vulnerability Assessment Outcomes by Classification Schemes for Vulnerability Components to Climate Change

Since the structural flood mitigation measures are limited due to climate change, preemptive measures are recently required by the flood vulnerability assessment, one of the nonstructural countermeasures to floods. Although the vulnerability assessment theory to climate change in IPCC (2001) is widely used for the flood vulnerability assessments, there is limited research on the effect of the classification schemes for vulnerability components on flood vulnerability evaluation outcomes. This study has therefore compared the two flood vulnerability results for 231 administrative districts in Korea under study, for which the one is a combination of the three vulnerability components to climate change such as exposure, sensitivity, and adaptability capacity, while the other is a combination of potential impact as a function of exposure and sensitivity along with adaptive capacity indicators. The results of this study are expected to provide basic information for selecting alternatives in flood mitigation plans. Keywords: Flood Vulnerability Assessment, Vulnerability to Climate Change, Assessment Indicator

Opening the floodgates to the recovery of nektonic assemblages in a temperate coastal wetland

Tidally active wetlands are important nurseries for fish and crustaceans; however, urban development involving structural flood mitigation has fragmented and destroyed much of this habitat, often leading to losses in fisheries productivity. The present study demonstrated that some of these impacts may be reversible if rehabilitation projects are implemented over a sufficiently long time. The incremental opening of eight floodgates at a temperate coastal wetland in Australia afforded the opportunity to monitor water quality and nekton assemblages in a tidal creek over 11 years, encompassing pre-floodgate opening, opening of one gate, three gates and finally all eight gates. Floodgate opening enhanced both water quality and nektonic assemblages relative to a control creek whose barrier remained in place. A doubling in species richness occurred and many commercially important species increased in abundance, including Metapenaeus macleayi (15 times more), Acanthopagrus australis (62 times more), Liza argentea (10 times more) and Gerres subfasciatus (19 times more). Recovery to a condition similar to unrestricted reference creeks was achieved once all eight gates were opened. The study illustrated that reinstating tidal flushing can recover nursery habitats and enhance populations of economically valuable species.

Evaluating the efficacy of distributed detention structures to reduce downstream flooding under variable rainfall, antecedent soil, and structural storage conditions

This research systematically analyzed the influence of antecedent soil wetness, rainfall depth, and the subsequent impact on peak flows in a 45km2 watershed. Peak flows increased with increasing antecedent wetness and rainfall depth, with the highest peak flows occurring under intense precipitation on wet soils. Flood mitigation structures were included and investigated under full and empty initial storage conditions. Peak flows were reduced at the outlet of the watershed by 3–17%. The highest peak flow reductions occurred in scenarios with dry soil, empty project storage, and low rainfall depths. These analyses showed that with increased rainfall depth, antecedent moisture conditions became increasingly less impactful. Scaling invariance of peak discharges were shown to hold true within this basin and were fit through ordinary least squares regression for each design scenario. Scale-invariance relationships were extrapolated beyond the outlet of the analyzed basin to the point of intersection of with and without structure scenarios. In each scenario extrapolated peak discharge benefits depreciated at a drainage area of approximately 100km2. The associated drainage area translated to roughly 2km downstream of the Beaver Creek watershed outlet. This work provides an example of internal watershed benefits of structural flood mitigation efforts, and the impact the may exert outside of the basin. Additionally, the influence of $1.8 million in flood reduction tools was not sufficient to routinely address downstream flood concerns, shedding light on the additional investment required to alter peak flows in large basins.

Environmental impact assessment of structural flood mitigation measures: a case study in Šiba, Slovakia

The proposed flood mitigation measures in the Slovak Republic are subject of environmental impact assessment (EIA) process before its approval. The paper elaborates and demonstrates the application of the risk analysis method for evaluating alternatives, which is core in EIA. Risk analysis is an appropriate tool to determine the level of the risk of the proposed flood mitigation measures and through which it is possible to choose the alternative with the lowest level of risk for the environment. The article presents the application of the developed methodology based on universal matrix of risk analysis in Siba village that is in existing flood risk. It analyses and discusses the results of the impact assessment from EIA practice in the Slovakia. The aim of the work is to improve existing qualitative and quantitative methods for assessing the impacts of proposed activities on the environment. Developed methodology stimulates creative approaches in searching of the best alternative to proposed activities (constructions) that are environmentally friendly. Innovation in this paper is presented by an implementation of universal matrix of risk analysis for flood mitigation measures (developed by the authors) for the purposes of EIA process.

Quantifying changes to historic fish habitat extent on north coast NSW floodplains, Australia

Global degradation of coastal ecosystems is influencing the provision of ecosystem services, including fisheries maintenance services. Degradation of the Australian coastal zone and its resources following European occupation has been recognised for some time. This includes the loss of ecologically important coastal wetlands, which have strong trophic and habitat links to fisheries. In NSW, structural flood mitigation works are a principle driver of the decline of coastal wetlands; however, little action has been taken to quantify the extent of decline due to limited information of the pre-European settlement extent of coastal wetlands. We use spatial data sets in GIS to quantify prime fish habitat and calculate the loss of fish habitat for the large coastal floodplains of northern NSW, which are significant contributors to the commercial and recreational fisheries of NSW. The technique is validated by comparison with early maps of wetland distribution. We identified pre-European distribution of available fish habitat of approximately 477,000 ha, of which 87,000 ha was identified as prime fish habitat. Approximately 62,000 ha of prime fish habitat was impacted by drainage of the coastal floodplains in association with flood mitigation works which intensified in the mid-1950s and were largely completed by 1971, equating to a loss of approximately 72 % of prime fish habitat. The declining value of the ecosystem services provided by prime fish habitat following drainage is likely to be substantial. Some actions have taken place to restore the functions of this habitat although significant opportunities remain to reverse this decline through management actions that restore natural drainage and reinstate tidal exchange. These actions become even more important as pressures on coastal wetlands increase with climate change and associated sea-level rise.

홍수방어시설용량-피해 매트릭스를 이용한 서울시 행정구역별 고유홍수취약성 평가

도시화의 속도가 빨라지고 있고, 기후변화 등으로 인해 극한 강우 등 이상기후현상이 자주 나타나고 있어 도시 홍수의 발생 빈도가 높아지고 있다. 그러므로 도시의 홍수취약성을 평가하고, 이에 따른 정책을 펼치는 것은 정책결정자에게 매우 중요한 일이며, 도시홍수방어의 역사가 길어짐에 따라 구조적인 홍수방어대책에 기 투자된 비용이 많은 지역은 과거와 달리 홍수피해가 거의 발생하지 않는 지역도 생기게 되었다. 그러므로 본 연구에서는 기존에 건설되었던 홍수방어시설이 작동하지 않을 경우, 특정 지역의 지형적인 요인 등으로 인해 필연적으로 홍수피해를 입어야만 하는 지역을 고유홍수취약성이 높은 지역이라고 정의하였다. 또한 제안된 고유홍수취약성과 현재의 홍수위험도를 나타내기 위한 방법으로 경영전략 분야에 자주 사용되는 BCG 매트릭스를 변형한 홍수방어시설용량-피해 매트릭스(PCD 매트릭스)를 제안하였다. PCD 매트릭스는 도시홍수방어를 위한 구조적 대책의 크기와 과거 홍수피해액을 이용하여 고유홍수취약성이 큰 지역과 현재 홍수위험도가 큰 지역을 구분한다. 서울시의 구별 자료를 활용하여 PCD 매트릭스를 그려본 결과, 상대적으로 홍수에 안전한 지역, 홍수에 취약한 지역, 고유홍수취약성이 커서 잠재적으로 홍수에 취약한 지역, 추가적인 홍수방어시설이 필요한 지역으로 구분하고, 기존의 취약성-탄력성 지수 결과와 비교하여, 기존의 방법에 비해 타당한 결과가 도출됨을 확인하였다. 예를 들어, 서울시의 송파구와 마포구의 경우 재정자립도가 높거나 홍수방어시설이 다수 구축되어 있어 기존 방법에 의하면 홍수취약성이 낮다고 알려져 있으나, 고유홍수취약성은 높은 지역으로 분류되었다. 이러한 결과는 홍수방재 정책 결정에 있어 보다 폭넓은 시각을 제공할 것으로 판단된다. Due to the rapid urbanization rate and extreme rainfall as a form of the abnormal climate, the urban flood frequency has been increased. Therefore, it is very important for the policy makers to evaluate the urban flood vulnerability and propose the corresponding flood mitigation policies. Since the interests on the urban flood mitigation is increased, many structural flood measures has been constructed. If a city has many structural flood measures, the city is considered as the flood safe city. In this study, inherent flood vulnerability is proposed using Flood Protection Capacity and Damage(PCD) matrix with the flood damage cost and constructed structural flood mitigation measures. The proposed inherent flood vulnerability method was applied in Seoul. The results are categorized by four areas such as relatively flood safe area, flood risk area, inherent flood vulnerable area, and the area where more structural flood measures are needed. Calculated inherent flood vulnerabilities were compared to the conventional flood vulnerability-resilience indices. The proposed inherent flood vulnerability showed more reasonable results. For example, Songpa and Mapo were considered as the flood safe districts because of its high financial independence rate and many constructed flood mitigation measures. However, their inherent flood vulnerability is relatively high. There results could show the comprehensive aspect on the flood mitigation policies.

Environmental impact assessment using a utility-based recursive evidential reasoning approach for structural flood mitigation measures in Metro Manila, Philippines

In recent years, the practice of environmental impact assessment (EIA) has created significant awareness on the role of environmentally sound projects in sustainable development. In view of the recent studies on the effects of climate change, the Philippine government has given high priority to the construction of flood control structures to alleviate the destructive effects of unmitigated floods, especially in highly urbanized areas like Metro Manila. EIA thus, should be carefully and effectively carried out to maximize or optimize the potential benefits that can be derived from structural flood mitigation measures (SFMMs). A utility-based environmental assessment approach may significantly aid flood managers and decision-makers in planning for effective and environmentally sound SFMM projects. This study proposes a utility-based assessment approach using the rapid impact assessment matrix (RIAM) technique, coupled with the evidential reasoning approach, to rationally and systematically evaluate the ecological and socio-economic impacts of 4 planned SFMM projects (i.e. 2 river channel improvements and 2 new open channels) in Metro Manila. Results show that the overall environmental effects of each of the planned SFMM projects are positive, which indicate that the utility of the positive impacts would generally outweigh the negative impacts. The results also imply that the planned river channel improvements will yield higher environmental benefits over the planned open channels. This study was able to present a clear and rational approach in the examination of overall environmental effects of SFMMs, which provides valuable insights that can be used by decision-makers and policy makers to improve the EIA practice and evaluation of projects in the Philippines.