Moderate Flood Research Articles

Mapping and Assessment of Flood Risk in the Wadi Al-Lith Basin, Saudi Arabia

Flood risk mapping is vital in watershed management and planning, especially in reducing flood damages. In this study, a flood risk map was developed for the Wadi Al-Lith watershed (Saudi Arabia) by combining geographic information system techniques with a multi-criteria decision-making method known as the Analytical Hierarchy Process (AHP). Several factors were investigated in the study, including elevation, slope, topographic wetness index, drainage density, rainfall, soil and land use, and land cover. The watershed was divided into five regions: very high, high, moderate, low, and very low flooding danger areas. The results showed that 35.86% of the total watershed area is under high and very high flood risks, while 26.85% of the total area is under a moderate flood risk. Less than 38% of the total watershed area was under a low flooding risk. The results of the developed model were validated with the flooding event that occurred on 23 November 2018 in the study area. The model was also compared with the flood mapping of the 100-year return period generated by the HEC-RAS software. Both the developed model and the HEC-RAS software showed similar results. The findings demonstrated that the developed model could be used to develop flood risk maps, especially in watersheds that experience scarcity and shortages in the short-interval rainfall measurements and the stream flow gauges (e.g., Wadi Al-Lith watershed and other watersheds in Saudi Arabia). Additionally, the obtained results can provide helpful knowledge for the policy- and decision-makers to make the right decisions regarding the effectiveness of the protective structures of the study area against the risk of flash flooding in the future.

Migrating bars influence the formation and dynamics of their peers in large sandy‐gravel bed rivers

AbstractThe present study investigates the morphodynamic interactions between migrating bars in a sandy gravel and nearly straight channel of the Loire River (France). From a large dataset collected from field campaigns performed between 2016 and 2020, we analysed the deflection power exerted by bars on flow and sediment transport that influences the dynamics of other bars present in the channel. We also investigated the role of low flows in bar formation. To this aim, the riverbed evolution has been documented using four years of bathymetrical and aDcp surveys. Flow deflection induced by the presence of bars in the channel differs for pre‐existing (first‐order) bars and bedload sediment accumulations identified as new developing bars (second‐order bars). The latter needs to reach an equilibrium size to influence flow direction. During low flows, first‐order bars emerge and create contraction/expansion zones in the channel, inducing a temporary local geometrical forcing that leads to sediment deposition at the outlet of these zones. Sediment deposited in these specific areas can constitute a nucleus for second‐order bar formation or contribute to first‐order bar aggradation. According to the linear free bar theory, the critical discharge that contributes to expressing an alternate bar pattern is exceeded during moderate flood, leading to the observation of a transitional bar pattern between alternate and central bar pattern.

Setting the stage: How abrupt climate change, geomorphic thresholds, and drought control flood response in the lower Tennessee River, USA

Extreme floods, with multi-century to millennia recurrence intervals, arise from a combination of antecedent watershed characteristics and unusual or rare atmospheric circulations that occur too infrequently to discern drivers from instrumental records. Few stream gauge records in the United States contain 100 years or more of annual peak flow data, meaning rare extreme floods are underrepresented in the peak flow population. We synthesized approximately 8,000 years of paleoflood hydrologic data from multiple studies and various landforms (floodplains, rock shelters, and caves) conducted in the Tennessee River Valley between Chattanooga, Tennessee, and Florence, Alabama, to examine Holocene flood variability. Extreme floods (>11,000 m3/s) clustered around ∼7,900, 6,000–4,900, and ∼1,000–80 cal yrs BP. More moderate floods occurred between 4,800 and 2,000 cal yrs BP. We compared flood variability in the Tennessee Valley to Holocene paleorecords available in North America. All periods of extreme flooding occurred during large-scale, abrupt climate transitions that lacked a distinct directionality of temperature change (i.e., warm to cool or cool to warm). Our findings indicate that extreme floods clustered in times when (1) warm-season precipitation increased, (2) abrupt increases in precipitation followed episodes of drought, and (3) the rate of change in the hydroclimate regimes was greater than the rate of morphological change in response to increased moisture, thus, exceeded geomorphic thresholds. Internal river basin factors such as drought-induced watershed changes and river morphological changes are key flood drivers that set the stage for flood response to changes in precipitation. Our findings suggest that anticipated changes to drought and precipitation intensity due to modern climate change may increase extreme floods, particularly for urban and regulated rivers not given the space for adjusting to higher precipitation variability.

Mapping Potential Soil Water Erosion and Flood Hazard Zones in the Yarlung Tsangpo River Basin, China

The ubiquity of soil water erosion in the Yarlung Tsangpo River Basin leads to a series of natural hazards, including landslides, debris flows and floods. In this study, the Revised Universal Soil Loss Equation model (RUSLE) was used to quantify potential soil water erosion, while the Height Above Nearest Drainage model (HAND) was used to delimit potential flood hazard zones. Remote sensing and geographic information system technologies were employed to spatialize the results, which showed that the annual soil loss from water erosion was less than 1239 t ha−1 y−1. The total soil loss was estimated to be over 108 × 106 tons, of which about 13 × 106 tons (12.04% of the total) occurred from the agricultural land in the downstream valley. Soil erosion mapping was performed using six levels of soil erosion intensity and the effects of precipitation, land use/land cover and topography on soil erosion were revealed. Increases in precipitation and slope gradient significantly increased the soil loss rate, while the maximum rate of soil loss occurred from densely vegetated land, reaching 9.41 t ha−1 y−1, which was inconsistent with erosion preconceptions for this land type. This may be due to a combination of the region’s unique climate of high intensity rainfall and steep slopes. Flood hazard mapping showed that all regional cities were located in a flood hazard zone and that, within the total basin area (~258 × 105 ha), 9.84% (2,537,622 ha) was in a high flood occurrence area, with an additional 1.04% in aa vulnerable to moderate flood hazard area. Approximately 1.54% of the area was in a low flood risk area and 4.15% was in a very low flood risk area. The results of this study provide an initial identification of high-risk soil water erosion and flood hazard locations in the basin and provide a foundation upon which decision-makers can develop water and soil conservation and flood prevention policies.

Extreme Rainfall and Flood Risk Prediction over the East Coast of South Africa

Extreme rainfall associated with mid-tropospheric cut-off low (COL) pressure systems affected the entire east coast of South Africa during April 2022, leading to flooding and destruction of homes, electricity power lines, and road infrastructure, and leaving 448 people confirmed dead. Therefore, this study investigated the evolution of the two COLs and their impacts, including the occurrence of extreme rainfall and cold weather over the southeast coast of the country. We analysed observed and reanalysis meteorological data and mapped areas at risk to impacts of flood hazards on the east coast of South Africa. Extreme rainfall (>500 mm) accumulated over 16 days was observed along the east coast, with the amount of rainfall progressively decreasing inland. We found that the rainfall associated with the first COL was significantly enhanced by the interactions between a strong low-level onshore airflow across the Agulhas Current and the coastal escarpment, resulting in deep convection and lifting. An unusual surface cyclone with tropical characteristics developed over the subtropical southwest Indian Ocean, driving onshore southeasterly winds which enhanced low-level convergence. Moreover, the flood risk results revealed that, amongst others, land cover/use (52.8%), elevation (16.8%) and lithology (15.5%) were the most important flood predictor variables in this study. Much of the study area was found to have very low (28.33%), low (31.82%), and moderate (21.66%) flood risk, whilst the high- and very-high-risk areas accounted for only 17.5% of the total land area. Nonetheless, the derived flood risk map achieved an acceptable level of accuracy of about 89.9% (Area Under Curve = 0.899). The findings of this study contribute to understanding extreme rainfall events and the vulnerability of settlements on South Africa’s east coast to flood risk, which can be used towards natural disaster risk reduction.

Used of Geospatial tools to detect the Flood Hazards in Dibru River Basin, Assam (India)

Mapping of Flood hazards is an essential component of land use planning. It creates awareness among the mass people about the impact of floods within the region. This study mainly focuses on the flood hazards within the Dibru River Basin. The region is the plain region near the bank of the river, or in the low land area where flood inundation is being observed. The primary aim of this study is to categorize the region into a very high flood zone, moderate flood zone and low flood zone. Different parametric are used in order to prepare the flood hazards mapping. GIS plays a vital role in processing all these parameters at one platform. GIS tool is frequently used to prepare flood hazard maps. It provides an effective way of assembling information from different maps. It can support planning and development by identifying high-risk locations and steering development away from them.

Effects of flooding outweigh those of vegetation restoration on key processes of carbon and nitrogen cycling in a degraded riparian zone

Active revegetation (AR) and natural regeneration (NR) are two restoration approaches widely used to rehabilitate degraded riparian ecosystems, which are subjected to frequent hydrological fluctuations owing to climate change and human activities. Nevertheless, the impacts of restoration approaches and hydrological changes on the key processes of carbon and nitrogen cycling, particularly in degraded riparian ecosystems, remain unclear. In this study, we conducted hydrological experiments, which began in 2016, at three flooding zones (extreme flooding zone, severe flooding zone, and moderate flooding zone) of AR and NR areas in the Three Gorges Reservoir to investigate the effects of restoration approach and hydrological changes on soil properties, vegetation diversity, microbial characteristics, denitrification rates, and greenhouse gas fluxes. The results showed that compared with NR, AR did not change vegetation diversity, microbial diversity, and soil denitrification rates, but decreased soil ammonium and total carbon contents. The vegetation coverage of each flooding zone was more than 90%, and vegetation diversity was relatively high in the moderate flooding zone. Moreover, the maximum denitrification rates and CO2 fluxes were observed in the extreme flooding zone along with a high soil nutrient content. Additionally, the effect of flooding zone superseded the impacts of restoration approaches since AR could only significantly increase the CO2 flux (p < 0.05). Overall, this study elucidates the impacts of restoration approaches and hydrological changes on C and N cycling, and aids in developing restoration strategies for degraded riparian ecosystems.

The Elephant Marsh, Malawi – Part 2: two-dimensional hydrodynamic modelling in support of an eco-social assessment

The Elephant Marsh lies on the floodplain of the lower Shire River, in southern Malawi. It is both a cultivated, seasonal floodplain and a wetland, characterised by a complex mosaic of meandering channels, marshland and shallow lakes. In 2016, the Marsh was granted RAMSAR status based on a series of supporting studies, including the modelling of eco-social options for managing its ecological condition. This paper describes two-dimensional (2-D) hydrodynamic modelling using RMA2, in support of this eco-social assessment. The hydraulic model was parameterised using mostly existing data but augmented with bathymetric channel and lake surveys. Calibration and verification used water level data from the hydrometric network for the period 1999 to 2009. Generally, observed water level time-series are well replicated in the model, but there are large discrepancies prior to this period. These are due to temporal changes in hydraulic controls, mainly sedimentation, but also breaching of an embankment at the downstream end of the Marsh. Selected hydraulic-habitat variables (based on daily hydrological time-series 1976 to 2009) provide the indictors of hydrological and hydraulic change used to inform a DRIFT eco-social assessment. The Marsh displays moderate flood attenuation characteristics, but the importance of this will likely increase under continued sedimentation and predicted climate futures, which include more severe storms. The 2-D modelling contributes to an improved understanding of the Marsh’s hydraulic behaviour, particularly regarding anthropogenic influences since the early 1900s.

Flood vulnerability and economic valuation of small and medium-sized enterprise owners to enhance sustainability.

Small and medium-sized enterprises (SMEs) play an important role in supporting Indonesia’s economic growth and provide employment for people. Nevertheless, SMEs are most vulnerable when there is a flood. Small and medium sized enterprises are worse off especially after the flood, because they are relatively limited in resources and less resilient. The study aimed at identifying the vulnerability level to floods and analysing the economic valuation of flood mitigation. The population in this study were SMEs located in flood-prone areas in Klaten Regency, Central Java province, Indonesia. This research used a purposive sampling technique with 152 respondents. Data collection was carried out using a direct interview method to business actors with the help of a questionnaire. There were two analytical tools used in this research, including vulnerability index and economic valuation. The results showed that Klaten Regency is located in the upper area vulnerability category of moderate flood. The economic valuation of flood mitigation is IDR 100 000 (USD6.99) to IDR 149 999 (USD10.49). Most SMEs perceive that flood mitigation is the responsibility of the government.

Modeling the relative morphodynamic influence of vegetation and large wood in a dryland ephemeral stream, Arizona, USA

Compared to perennial streams, studies investigating the impact of large wood on sediment transport and river corridor morphology in ephemeral streams are lacking. Due to the flashy nature of ephemeral flow regimes, opportunities to directly investigate the influence of wood in ephemeral channels are limited. Additionally, given prior studies showing a strong association between existing riparian vegetation and large wood deposition in ephemeral streams, the geomorphic impact of wood is entangled with that of vegetation. Here, we develop a hydro-morphodynamic model to investigate changes to channel and floodplain morphology due to wood and vegetation in an ephemeral stream in southeastern Arizona, USA. Three scenarios are modeled: the actual configuration of the river corridor; an experiment in which jams are removed; and an experiment in which vegetation is removed. Both large wood and vegetation effectively confined flow to the main, unvegetated channel, which became wider and deeper over the course of a single moderate flood. When isolating the impact of large wood, model results show that wood enhances channel change created by vegetation, resulting in ±0.1 to 0.3 m of additional scour or aggradation. The simulated removal of vegetation resulted in more channel change than the removal of wood alone, partially because vegetation occupies a much greater area within the stream corridor than large wood. We propose a conceptual framework where large wood could mediate sedimentation as well as the recruitment and growth of vegetation in ephemeral streams, contributing to the evolution of ephemeral stream morphology over time.

Flood vulnerable zones mapping using geospatial techniques: Case study of Osogbo Metropolis, Nigeria

Several Areas within Osogbo, the capital city of Osun State in Nigeria, have suffered severely from incessant flood occurrences, which necessitated flood vulnerability mapping. This research aimed to map out flood vulnerable areas within Osogbo Metropolis using geospatial techniques to facilitate fitting planning and proffer lasting solutions to the frequent damage that humans and their properties suffer from flooding within the city. Satellite data of Osogbo Metropolis were processed and analyzed in a GIS environment for flood vulnerable zones mapping. Eight (8) flood causative factors were combined in this study using Analytic Hierarchy Process (AHP). The factors are Stream Proximity (SP), Drainage Density (DD), Elevation, Slope, Stream Power Index (SPI), Topographic Wetness Index (TWI), Normalized Difference Vegetation Index (NDVI), and Land Use/Land Cover (LULC). Results revealed that approximately 24% of the total area of study falls within the high flood vulnerable zones, while 21% and 55% fall within the moderate and low flood vulnerable zones, respectively. A close agreement between the flood vulnerable zones and previous flood incidences across the study area established the accuracy of the methodology. This study's established flood vulnerable zones will guide the respective policymakers during discussions on preventing flood disasters within the Osogbo metropolis.

Compound Effects of Flood Drivers, Sea Level Rise, and Dredging Protocols on Vessel Navigability and Wetland Inundation Dynamics

Maritime transportation is crucial to national economic development as it offers a low-cost, safe, and efficient alternative for movement of freight compared to its land or air counterparts. River and channel dredging protocols are often adopted in many ports and harbors of the world to meet the increasing demand for freight and ensure safe passage of larger vessels. However, such protocols may have unintended adverse consequences on flood risks and functioning of coastal ecosystems and thereby compromising the valuable services they provide to society and the environment. This study analyzes the compound effects of dredging protocols under a range of terrestrial and coastal flood drivers, including the effects of sea level rise (SLR) on compound flood risk, vessel navigability, and coastal wetland inundation dynamics in Mobile Bay (MB), Alabama. We develop a set of hydrodynamic simulation scenarios for a range of river flow and coastal water level regimes, SLR projections, and dredging protocols designed by the U.S. Army Corps of Engineers. We show that channel dredging helps increase bottom (‘underkeel’) clearances by a factor of 3.33 under current mean sea level and from 4.20 to 4.60 under SLR projections. We find that both low and high water surface elevations (WSEs) could be detrimental, with low WSE (&amp;lt; -1.22 m) hindering safe navigation whereas high WSE (&amp;gt; 0.87 m) triggering minor to major flooding in the surrounding urban and wetland areas. Likewise, we identify complex inundation patterns emerging from nonlinear interactions of SLR, flood drivers, and dredging protocols, and additionally estimate probability density functions (PDFs) of wetland inundation. We show that changes in mean sea level due to SLR diminish any effects of channel dredging on wetland inundation dynamics and shift the PDFs beyond pre-established thresholds for moderate and major flooding. In light of our results, we recommend the need for integrated analyses that account for compound effects on vessel navigation and wetland inundation, and provide insights into environmental-friendly solutions for increasing cargo transportation.

Physiological Adaptation and Plant Distribution along a Steep Hydrological Gradient.

Plant species often separate strongly along steep environmental gradients. Our objective was to study how coupling between plant physiology and environmental conditions shapes vegetation characteristics along a distinct hydrological gradient. We therefore investigated species photosynthesis in air and under water within a limited area from dry-as-dust to complete submergence in a nutrient-poor limestone habitat on Öland’s Alvar, Sweden. We found structural and physiological adaptations of species to endure water limitation at the dry end (e.g., moss cushions and CAM-metabolism) and diffusive carbon limitation (e.g., bicarbonate use) at the submerged end of the gradient. As anticipated, mean photosynthesis in air increased 18-fold from the species-poor assembly of cushion-mosses and Sedum CAM-species on mm-thin limestone pavements to the species-rich assembly of C-3 terrestrial plants in deeper and wetter soils. A GLM-model indicated that 90% of the variation in species richness could be explained by a positive effect of soil depth, a negative effect of the duration of water cover and their interaction. In water, mean photosynthesis was highest among aquatic species, low among Sedum species and cushion mosses, and negligible among C-3 terrestrial plants. While aquatic species dried out in air, drought-resistant small species were probably competitively excluded from the more suitable terrestrial habitats on deeper soils with moderate flooding by taller species of high photosynthetic capability. In conclusion, the clear distribution of species along the steep hydrological gradient reflects distinct structural and physiological adaptations, environmental filtering and interspecific competition.

Channel Conveyance Variability can Influence Flood Risk as Much as Streamflow Variability in Western Washington State

AbstractChanges in the severity and likelihood of flooding events are typically associated with changes in the intensity and frequency of streamflows, but temporal adjustments in a river's conveyance capacity can also contribute to shifts in flood hazard. To assess the relative importance of channel conveyance to flood hazard, we compare variations in channel conveyance to variations in the flow magnitude of moderate (1.2 years) floods at 50 river gauges in western Washington State between 1930 and 2020. In unregulated rivers, moderate floods have increased across the region, but in regulated rivers this trend is suppressed and in some cases reversed. Variations in channel conveyance are ubiquitous, but the magnitude and timing of adjustments are not regionally uniform. At 40% of gages, conveyance changes steadily and gradually. More often, however, conveyance variability is nonlinear, consisting of multidecadal oscillations (36% of gages), rapid changes due to unusually large sediment‐supply events (14% of gages), and increases or decreases to conveyance following flow regulation (10% of gages). The relative importance of conveyance variability for flood risk depends on the mode of adjustment; in certain locations with historic landslides, extreme floods, and flow regulation, the influence of conveyance changes on flood risk matches or exceeds that of streamflow at the same site. Flood hazard management would benefit from incorporating historic long‐term and short‐term conveyance changes in predictions of future flood hazard variability.

Amplification of downstream flood stage due to damming of fine-grained rivers

River dams provide many benefits, including flood control. However, due to constantly evolving channel morphology, downstream conveyance of floodwaters following dam closure is difficult to predict. Here, we test the hypothesis that the incised, enlarged channel downstream of dams provides enhanced water conveyance, using a case study from the lower Yellow River, China. We find that, although flood stage is lowered for small floods, counterintuitively, flood stage downstream of a dam can be amplified for moderate and large floods. This arises because bed incision is accompanied by sediment coarsening, which facilitates development of large dunes that increase flow resistance and reduce velocity relative to pre-dam conditions. Our findings indicate the underlying mechanism for such flood amplification may occur in >80% of fine-grained rivers, and suggest the need to reconsider flood control strategies in such rivers worldwide.

The impact of flooding on rice production in the Krueng Kluet Watershed, Aceh Province, Indonesia

Kluet Utara is a sub-district in South Aceh Regency, Aceh Province. This sub-district is the largest rice field area in South Aceh Regency with an area of ± 1,627.34 Ha. Currently, lowland rice farmers in this district often suffer losses due to flooding from the Krueng Kluet watershed which has an impact on crop failure and the drifting of rice production that is carried away by flood currents, this greatly affects the decline in lowland rice production. This study aims to examine correlation the impact of flooding on lowland rice production and the relationship between flood-prone areas and the of lowland rice production in Kluet Utara Regency. In conclusion, before the flood the total production was 9,827 tons, productivity was 6.03 tons/ha. Meanwhile, when there was a flood, the production of lowland rice was 2,827 tons, the productivity was 1.73 tons/ha. The relationship of lowland rice production with moderate and high flood areas has a very strong correlation value. That is, there is a very large relationship on the decline in production during a flood, while in very high flood areas there is a correlation between the impact of flooding on a decrease in rice production.

Study Of Flood Disaster Risk Delta In Bojonegoro Regency

A disaster is an unexpected and often sudden event that causes destruction, serious damage, and human suffering. According to the Law of the Republic of Indonesia Number 24 of 2007 concerning Disaster Management, disasters are caused by natural factors and/or non-natural and human factors so that disasters can result in loss of life, environmental damage, loss of property, and psychological impacts. Bojonegoro Regency which has the widest area crossed by the Bengawan Solo river and 24,753 hectares of its area is a watershed so that almost every year Bojonegoro Regency is flooded when the Bengawan Solo river overflows. Floods in Bojonegoro Regency almost occur every year. Where the flood that occurred in Bojonegoro Regency was caused by the overflow of the Bengawan Solo river. As much as 63% of the total population of Bojonegoro Regency is exposed or at risk of flooding in 2012 to 2020. This study is to determine the Delta (Δ) risk of flood-prone areas in Bojonegoro Regency based on trends in land use change with a multitemporal perspective in Bojonegoro Regency. This study uses the latest methods, especially in terms of spatial modeling, namely TIN and Raster databases. The first step is to predict the trend of land use in Bojonegoro Regency. Which is then continued to identify flood hazards and land use vulnerabilities. Flood disaster-prone areas each year are predicted based on the previous stages using the Analytic hierarchy process which then produces disaster risk in each prediction year. The last step is to calculate the amount of change or Delta (∆) of Flood Disaster Risk in Bojonegoro Regency. The results of this study are Delta (∆) Low Flood Disaster Risk: experienced a change of -1.62% or decreased by 49.66 Ha from 2020 to 2040. Delta (∆) Moderate Flood Disaster Risk: experienced a change of 2.85% or experienced an increase of 17.67 Ha from 2020 to 2040. Delta (∆) High Flood Risk: experienced a change of 23.96% or an increase of 31.99 Ha from 2020 to 2040.

Can the “10-year fishing ban” rescue biodiversity of the Yangtze River?

Can the “10-year fishing ban” rescue biodiversity of the Yangtze River?

Differential Responses of Native Fishes in Two Headwater Tributaries of the Gila River Following Severe Wildfires

High-severity wildfires are becoming increasingly common across the American Southwest, and knowledge of how these fires affect native organisms is essential for their conservation. We evaluated changes in fish densities and habitat over 7 and 23 years in 2 tributaries of the Gila River, New Mexico, that experienced large wildfires. The Miller Fire affected Little Creek in 2011 and was followed by moderate monsoonal flooding. The Silver Fire affected Black Canyon in 2013 and was followed by a large monsoonal flood. These 2 headwater streams responded differently to wildfire. Influx of sediments reduced stream depth by 59% and increased fine substrates by 51% following the fire in Black Canyon, while these parameters were relatively unchanged by fire in Little Creek. Native fish densities declined to zero immediately following the wildfire and monsoonal flooding in Black Canyon, and recovery was slow (∼8 years). In contrast, Little Creek fish density declined marginally following wildfires and returned to near prefire levels within one year. The response to wildfires at these 2 locations illustrates how the interaction of wildfire characteristics, catchment features, and post-wildfire precipitation events influence the impact of wildfire disturbance of stream ecosystems.

The effects of extreme climate on the invasive plant Gutenbergia cordifolia: implications for its future management in savannah ecosystems

The aim of this study was to assess the effects of varying water stress levels on morphological and physiological parameters of an invasive plant Gutenbergia cordifolia. The assessment was conducted in the screenhouse at the Nelson Mandela African Institution of Science and Technology following a completely randomized design (CRD). Both morphological and physiological parameters were variable under water stress levels. While the maximum (159 cm) and minimum (9 cm) plant heights for G. cordifolia were observed under flood and drought water stress respectively, its maximum root collar diameter of 5 mm and the minimum of 1.3 mm were observed under moderate flood and drought water stress respectively. Generally, the number of leaves was highest under moderate flood stress (194 leaves/plant), and lowest under drought stress (13 leaves/plant). Similarly, the largest and smallest leaf surface area of 9 × 103 and 1 × 103mm2 were observed under flood and drought water stress respectively due to G. cordifolia's tendency to retain water when exposed to water stress through a reduction in number of leaves and leaf surface area when under drought stress condition. While a decrease in leaf chlorophyll was observed across water stress levels with the lowest chlorophyll levels of 0.02 under drought water stress, an increase in leaf anthocyanin levels (0.29 Abs g.DM−1) was observed particularly under flood stress due to increased chlorophyll breakdown and plants' water stress, respectively. This study informs that extreme climatic events such as excessive floods will likely facilitate invasions by G. cordifolia leading to decreased biotic resistance of native communities in savanna rangelands. Efforts to manage G. cordifolia's effects in a changing climate must therefore include the development of strategies and action plans that account for catastrophic events like floods and drought.