Increase In Peak Flow Research Articles

The Coupled Application of the DB-IWHR Model and the MIKE 21 Model for the Assessment of Dam Failure Risk

The phenomenon of global climate change has led to an increase in the frequency of extreme precipitation events, an acceleration in the melting of glaciers and snow cover, and an elevation of the risk of flooding. In this study, the DB-IWHR model was employed in conjunction with the MIKE 21 hydrodynamic model to develop a simulation system for the dam failure flow process of an earth and rock dam. The study concentrated on the KET reservoir, and 12 dam failure scenarios were devised based on varying design flood criteria. The impact of reservoir failures on flood-risk areas was subjected to detailed analysis, with consideration given to a range of potential failure scenarios and flood sizes. It was determined that under identical inflow frequency conditions, the higher the water level, the more rapid the breakout process and the corresponding increase in flood peak discharge. Conversely, for a given frequency of incoming water, an elevated water level results in a transient breach process, accompanied by a reduction in flood peak flow. Moreover, for a given water level, an increase in water frequency results in a reduction in breaching time, an extension of flood duration, and an increase in flood peak flow. The observed trend of flood spreading is generally north-south, and this process is highly compatible with the topographic and geomorphological features, demonstrating good adaptability.

Longitudinal study on peak expiratory flow monitoring and its impact on quality of life in childhood asthma

Objective To evaluate the impact of peak expiratory flow (PEF) monitoring using a smart peak flow (SPF) device on the quality of life (QoL) and satisfaction among children with asthma. Methods This 3-month prospective cohort study enrolled 71 children aged 7 to 17 years with physician-diagnosed asthma. Participants used the SPF device twice daily, with measurements recorded automatically. Quality of life was assessed using the Pediatric Asthma Quality of Life Questionnaire (PAQLQ), and asthma control was assessed using the Asthma Control Test (ACT) or Childhood Asthma Control Test (C-ACT). Adherence to PEF measurements and satisfaction with the device were evaluated. Results Seventy-one children (mean age 11.4 years) completed the study. Adherence to twice-daily PEF measurements decreased significantly over three months (from 50.0% at 1 month to 39.9% at 3 months, p < 0.001). Children with good adherence (38.0%) showed significant improvements in PAQLQ scores, while those with poor adherence (62.0%) did not. COVID-19 infection resulted in a significant decrease in %PEF rate and increased peak flow variability. Despite device-related issues, overall satisfaction was high (85.19% for good adherence users vs. 88.64% for poor adherence users, p = 0.671). Conclusion Regular PEF monitoring improves QoL in children with asthma by enabling early detection of symptom changes and better management. However, maintaining adherence to regular PEF monitoring is challenging. Further research with control groups is needed to validate these findings.

Stormwater characterisation and modelling for Sungai Air Hitam in Selangor, Malaysia using model for urban stormwater improvement conceptualisation (music)

The aim of this study is to evaluate the current water quality status of one of the urban rivers in Malaysia, called Sungai Air Hitam. The river's water supply is not only unsuitable for the inhabitants but also hazardous to the aquatic species that depend on it. In order to simulate the water quality formulation of the river, the Model for Urban Stormwater Improvement Conceptualization (MUSIC) was used. The effects of various best management practices (BMPs) components have been examined to improve the river's water quality. This study also investigated different scenarios of the expected future changes in the land cover and the quality of the river. As the proportion of impervious surfaces increases, the urban hydrology cycle can be significantly altered, resulting in an increase in volumes and peak flows, and a decrease in storage, infiltration, and interception. The MUSIC results have shown significant reductions in biochemical oxygen demand (BOD), total suspended solids (TSS), total phosphorus (TP), and total nitrogen (TN) after introducing BMPs. It was also noticed that the prediction of pollutants falls within the acceptable range set by the Urban Stormwater Management Manual for Malaysia (MSMA) 2nd edition. For the land cover, it was found that the total reduction of BOD, TSS, TP, and TN for existing land use is 92.5 %, 94.5 %, 90.7 % and 91.9 %. Meanwhile, the total reduction in future land use is 81.6 % for BOD, 86.2 % for TSS, 80.9 % for TP and 80.8 % for TN. From the simulation results, it was observed that the application of BMPs has successfully reduced the observed mean BOD concentration from 92.38 mg/L (Class V) to 6.93 mg/L (Class IV) of the national water quality standards, NWQS, water quality index. As a result, the water quality index of the overall catchment has improved from Class IV to Class III (WQ1, WQ3, and WQ4) and from Class V to IV (WQ2) with the application of the BMPs. This assessment aims to raise awareness within the Sungai Air Hitam community regarding the importance of preserving river cleanliness and understanding the long-term environmental impact of water quality. These findings underscore the importance of an integrated system in managing urban water systems, which can offer valuable insight to the decision-makers.

Effects of urbanization and accessibility to sanitation services on water quality in urban streams in Uruguay.

The world's urban population is growing rapidly, and threatening natural ecosystems, especially streams. Urbanization leads to stream alterations, increased peak flow frequencies, and reduced water quality due to pollutants, morphological changes, and biodiversity loss, known as the urban stream syndrome. However, a shift towards recognizing urban streams as valuable natural systems is occurring, emphasizing green infrastructure and nature-based solutions. This study in Uruguay examined water quality in various watersheds with different urbanization levels and socio-environmental characteristics along a precipitation gradient. Using Geographic Information Systems (GIS) and in situ data, we assessed physicochemical parameters, generated territorial variables, and identified key predictors of water quality. We found that urbanization, particularly urban areas, paved areas, and populations without sanitation, significantly influenced water quality parameters. These factors explained over 50% of the variation in water quality indicators. However, the relationship between urbanization and water quality was non-linear, with abrupt declines after specific urban intensity thresholds. Our results illustrate that ensuring sanitation networks and managing green areas effectively are essential for preserving urban stream water quality. This research underscores the importance of interdisciplinary teams and localized data for informed freshwater resource management.

The impacts of rainfall and soil moisture to flood hazards in a humid mountainous catchment: a modeling investigation

Floods pose a significant threat to the safety of countries with severe societal, economic, and environmental consequences, especially the flash floods in mountainous regions. Previous studies have shown that many floods were caused by intense rainfall with highly saturated soil. In this study, we applied a physically-based distributed hydrological model (Integrated Hydrology Model, InHM) to a warm humid mountainous catchment in Southwest China, the Shouxi River. The main objective of our research is to investigate the relative importance of rainfall and antecedent soil moisture on flood generation in our study region. Our results show that an increase in rainfall return period and antecedent soil saturation ratio significantly increased peak flow and shortened peak time. There is a correlation between the ratio of antecedent soil saturation ratio to rainfall (SPR) and peak flow. When SPR &amp;lt;1, there is a positive correlation; when SPR &amp;gt;1, there is a negative correlation. Additionally, with the increase in drainage area, the relative importance of rainfall tends to decrease, while the relative contribution of soil saturation ratio tends to increase. The findings could provide support for the determination of the dominant factors influencing runoff generation in humid regions, offering scientific support for the timely and effective flood prevention and mitigation measures in mountainous regions.

Integrating the Spatial Configurations of Green and Gray Infrastructure in Urban Stormwater Networks

AbstractGreen infrastructure (GI) practices improve stormwater quality and reduce urban flooding, but as urban hydrology is highly controlled by its associated gray infrastructure (e.g., stormwater pipe network), GI's watershed‐scale performance depends on its siting within its associated watershed. Although many stormwater practitioners have begun considering GI's spatial configuration within a larger watershed, few approaches allow for flexible scenario exploration, which can untangle GI's interaction with gray infrastructure network and assess its effects on watershed hydrology. To address the gap in integrated gray‐green infrastructure planning, we used an exploratory model to examine gray‐green infrastructure performance using synthetic stormwater networks with varying degrees of flow path meandering, informed by analysis on stormwater networks from the Minneapolis‐St. Paul Metropolitan Area, MN, USA. Superimposed with different coverage and placements of GI (e.g., bioretention cells), these gray‐green stormwater networks are then subjected to different rainfall intensities within Environmental Protection Agency's Storm Water Management Model to simulate their hydrological benefits (e.g., peak flow reduction, flood reduction). Although only limited choices of green and gray infrastructure were explored, the results show that the gray infrastructure's spatial configuration can introduce tradeoffs between increased peak flow and increased flooding, and further interacts with GI coverage and placement to reduce peak flow and flooding at low rainfall intensity. However, as rainfall intensifies, GI ceases to reduce peak flow. For integrated gray‐green infrastructure planning, our results suggest that physical constraints of the stormwater networks and the range of rainfall intensities must be considered when implementing GI.

Evaluating Climate Change Effects on a Snow-Dominant Watershed: A Multi-Model Hydrological Investigation

Assessing the impact of climate change on water systems often requires employing a hydrological model to estimate streamflow. However, the choice of hydrological model, process representation, input data resolution, and catchment discretization can potentially influence such analyses. This study aims to evaluate the sensitivity of climate change impact assessments to various hydrological modeling configurations in a snow-dominated headwater system in Alberta, Canada. The HBV-MTL and GR4J models, coupled with the Degree-Day and CemaNeige snowmelt modules, were utilized and calibrated using point- and grid-based climate data on lumped and semi-distributed catchment discretization. The hydrological models, in conjunction with a water allocation model, were supplied with climate model outputs to project changes in the basin. While all models revealed a unanimous increase in peak flow, the difference between their estimations could be as substantial as 42%. In contrast, their divergence was minimal in projecting median flow. Furthermore, most models projected an aggravated water supply deficit between 16% and 40%. Overall, the quantified climate change impacts were the most sensitive to the choice of snow routine module, followed by the model type, catchment discretization, and data resolution in this snow-dominant basin. Therefore, particular attention should be given to the proper representation of snowmelt processes.

Assessing the effects of land cover change in runoff processes with RHESSys: a case study in the Waterford River Watershed, Newfoundland and Labrador, Canada

Evaluating the current state of hydrologic processes in urban and semi-urban areas is an essential part of ensuring the sustainable management of water and preventing emergencies of extreme events. This study evaluated the effects of land use and land cover (LULC) change on runoff processes in the Waterford River Watershed (WRW), located in the eastern part of the province of Newfoundland and Labrador (NL), Canada. The Regional Hydro – Ecological Simulation System (RHESSys), a GIS-based hydro-ecological model, was used in a new urbanistic approach to simulate the effects of increasing impervious land as well as reducing urban green areas. The increase in hypothetical peak flows had a direct relationship with the reduction of pervious areas in the watershed. The most sizeable flow increases were observed in the periods of April to May and October to December. This study emphasizes the importance of using a prominent network of green and pervious structures or water retention areas when allocation for residential and commercial land increase.

Modeling wildfire effects on streamflow in the Cascade Mountains, Oregon, USA

Increasing occurrence of large and severe wildfires represents a growing threat to forested watersheds and the many ecosystem services they provide. Past research has shown that wildfires can cause substantial increases in peak flows and annual water yields, leading to potential water quality concerns and land and water management challenges. However, responses have been variable, and there have been few studies at large basin scales, leading to uncertainties about post-fire hydrologic responses. To address these uncertainties, we projected the effect of three large wildfires (>70,000 ha) on streamflow in two important forested watersheds in the Cascade Range of Oregon, US. We modeled the streamflow response using the Soil and Water Assessment Tool (SWAT) model, calibrated on data from prior to the wildfires. We modified model parameters to represent the impacts of the wildfires based on burn severity maps. Burned and unburned scenarios were compared using random forest models to identify drivers of increased annual water yields and peak flows. Post-fire annual water yield changes were controlled by burn severity, annual precipitation, area burned, aridity, and vegetation type, while post-fire peak flow changes were controlled by burn severity, area burned, aridity, soil type, and geologic province. We also found that post-fire increases in annual water yields, peak flows, and low flows were greatest at the headwater scale but were more muted at the downstream basin scale. Our work provides valuable insights into the range of potential post-fire streamflow changes at the headwater and larger basin scale, which is becoming increasingly critical for effective forest and water management decisions.

River-floodplain interaction and flood wave routing along rivers flowing through Pantanal wetlands

The Pantanal is the largest tropical wetland in the world and has extraordinary biodiversity, being considered of great ecologic value. Besides the intimate dependence of Pantanal ecosystems, functioning, and integrity on water dynamics, the flood pulse and inundation also regulate traditional riverside communities’ way of life, recreational fishing tourism, jaguar tourism, cattle raising, navigation, and agriculture. This study advances in characterizing flood wave dampening, flood wave travel time, and lateral exchanges of water of rivers flowing along the Pantanal, investigating the relationship between these characteristics and the upstream flood. A dynamically coupled 1D-2D hydrological modeling approach, already calibrated on earlier work is used, to simulate the main channel flood wave routing, water inundating and moving across the floodplain, and channel-floodplain bidirectional interaction. Four upstream flooding scenarios were imposed, simulating contributing floods from uplands (Planalto), that enter and flow along each of the major rivers of the Pantanal region. The results indicate that flood wave travel time is directly related to the size of the upstream flood, but the presence of secondary peak flows before or after the major flood peak did not have a marked influence. Patterns of reduction or increase in peak flow along the river reaches were also identified, which were independent of the size and shape of the upstream flooding condition. For the uppermost reaches of all rivers, the loss of water from the main channel to the floodplain heavily attenuates the flood hydrograph. This flood dampening showed to be stronger for larger floods, as there is more proportion of channel flow spilling over to the floodplains. However, in absolute terms, these results showed that upstream floods of different sizes or with different shape characteristics (multiple or single peak flows) present quite similar flood hydrographs as one moves downstream along the Pantanal region, becoming typically unimodal smoothed flood hydrographs.

Adjusting design floods for urbanization across groundwater-dominated watersheds of Long Island, NY

The magnitude and variability of floods have increased for many nontidal streams on Long Island (LI), NY since the mid-20th century. One of the most densely populated regions of the United States, LI has experienced amplified floods in step with increases in impervious land cover, storm, and sanitary sewers that have accompanied urban development. To better understand the drivers of observed flood trends and effects of urbanization, a nonstationary flood frequency analysis is conducted, using historical annual peak flow records from 17 gaged watersheds on LI using conditional moments based on physical covariates from a two-stage sequential robust linear regression procedure. Regression results indicate that urban development and precipitation are significant co-predictors of peak flows for LI watersheds that have undergone rapid development during the available peak flow record. In watersheds with less intense urbanization or that were fully developed before the peak flow record began, precipitation alone was a significant explanatory variable. Long-term baseflow patterns identified using a nonparametric smoother explained some patterns of decreasing peak flows and heteroskedasticity in the peak flow records. Fitting a log-Pearson III distribution with these conditional moments, floods corresponding to a 20% annual exceedance probability (AEP) are up to 80% higher under a nonstationary framework compared with stationary under current watershed conditions, and differ significantly (95% confidence) from stationary estimates for 6 out of 17 watersheds. Larger floods corresponding to 1% AEPs do not differ significantly between nonstationary and stationary estimates at a 95% confidence level. Nonmonotonic trends observed in two watersheds indicate that recent stormwater management practices, such as rerouting stormwater outfalls away from the channel, substantially reduce flood frequency. Reduced nonstationary flood quantile estimates at these two watersheds are 20 to 40% lower than stationary estimates when accounting for changing watershed conditions over time. Across LI, stormwater management and water-table fluctuations have increased peak flow variability, characteristic of a late phase urban adjustment period on LI. Results of this study demonstrate that a nonstationary framework is a necessary step forward toward a regional flood-frequency analysis for LI. This nonstationary framework will allow flood managers to update flood discharge estimates to current conditions that reflect altered relationships between urban cover and climate for more targeted planning of flood control, transportation infrastructure, and management of floodplain ecosystems.

Hydrological Effects of Spatial Harvest Patterns in a Small Catchment Covered by Fast-Growing Plantations in the Neotropics

&lt;em&gt;Eucalyptus&lt;/em&gt; forests are expanding worldwide and concerns exist about their impact on water resources. There is a lack of information about the hydrological effects of spatial harvest patterns in terms of their effects on streamflow. In this paper, we examined harvest amount and hillslope position effects on flow indices (Q70; Q50 and Q10) and water yield in a small catchment covered with a fast-growing &lt;em&gt;Eucalyptus&lt;/em&gt; plantation. To do that, we used the Gridded Surface Subsurface Hydrologic Analysis (GSSHA), a physical-based distributed hydrological model, to simulate harvesting scenarios with different harvest amounts (30% and 70% of the forest plantation) at two hillslope positions (downslope and upslope). We also verified the influence of the amount of rainfall on peak flows for all scenarios. The results showed that the increase in water yield is positively related to the harvest amount and that, under the same harvest amount, harvests in downslope areas caused a larger increase in water yield than harvests in upslope areas. Downslope harvests led to a greater increase in peak flow under the 30% harvest. For the 70% harvest, no substantial effects of harvest position on peak flow could be detected. Incorporating harvest amounts and spatial patterns in &lt;em&gt;Eucalyptus&lt;/em&gt; plantations management practices may be useful to mitigate their effects on water resources, especially in regions where water availability is generally lower.

A new multi‐criteria framework to identify optimal detention ponds in urban drainage systems

AbstractUrban development broadly impacts the hydrological cycle, leading to increased peak flow and flooding. Surface water detention ponds are among the most efficient measures for attenuating peak flow and returning it from development to pre‐development conditions. However, the major challenge is identifying optimal locations and cost‐effective designs for these ponds. This paper presents a new framework for identifying the best strategies for using detention ponds to control floods in urban drainage systems (UDS). The framework comprises a portfolio of simulation tools coupled with evolutionary optimisation and multi‐criteria decision analysis models. Hydraulic simulation of UDS is first modelled using SWMM and GIS tools. A multi‐objective optimisation model was used to find the optimal location and design for detention ponds. The compromise programming (CP) multi‐criteria decision‐making method was then used to prioritise potential best management solutions for detention ponds based on several sustainability criteria comprising economic, environmental, physiographic and social factors. The results identified the key features of potential detention ponds appearing in all multi‐objective optimal solutions that are useful for decision‐makers/designers when planning/designing for new detention ponds. The selected optimal pond strategies can significantly improve the UDS performance by decreasing flood damage between 66% and 90% at the cost of between $50,000 and $160,000.

A Web-Based Application for Exploring Potential Changes in Design Peak Flow of US Urban Areas Driven by Land Cover Change

Floods have become increasingly prominent in recent decades causing devastating effects on lives and livelihoods worldwide. Efficient tools to assess the drivers of floods, such as increasing urbanization, could help to minimize flood hazards. Urbanization increases the design peak flow (maximum potential surface water flow from a precipitation event with an average probability of occurring once in a specific recurrence interval), which is a key information needed for designing stormwater management infrastructures such as culverts and storm sewers. A web-based application was developed to explore the potential changes (1985 to 2020) in design peak flow of urban areas across the conterminous United States driven by land cover change. The results indicate a potential increase in design peak flow in urban areas up to 126.6% in 2020 compared to 1985. Of the total 3,535 study urban areas, about 80% (2,840) urban areas increased design peak flow, and about 19% (654) decreased design peak flow. A general pattern of increasing design peak flow was observed during 1985 to 2010, and decreasing pattern was observed during 2010 to 2020, primarily driven by respective increasing (decreasing) and decreasing (increasing) developed areas (croplands). The application provides crucial information by visualizing both spatial and temporal data that could be useful for decision-makers in developing and improving urban stormwater management plans and policies for efficient resource allocations and reducing flood risks.

Application of PCSWMM for assessing the impacts of urbanization and climate changes on the efficiency of stormwater drainage systems in managing urban flooding in Robe town, Ethiopia

Study regionThis study was conducted in Robe town, Ethiopia. Study focusIn this, the PCSWMM was used to investigate the potential effects of climate change and land-use change on the peak flow magnitude and efficiency of stormwater drainage systems in managing urban flooding. Four simulation scenarios were developed to demonstrate the changes in the flooding volume and adequacy of existing systems. Moreover, the effectiveness of three low-impact developments: rain barrels, rain gardens, and a combination of both practices as a mitigation strategy in reducing flooding volume were investigated. New hydrological insights for regionThe trend of landuse change showed that the increased peak flow and flooding volume of junctions increased from 45.13 to 68.72 m3/s and 35,418–50,106 × 106 Ltr respectively, due to the imperviousness increasing from 10% to 70%. Similarly, in response to climate change, the simulated peak runoff increased by 46.9%, 34.8%, and 37.5% for, RCA4, RACMO22T, and REMO2009, respectively. This findings showed that if the current landuse and climate changes continue in the coming years, the study area threatened by the increased flooding due to the drainage systems will fail to accommodate increased peak runoff. The present study suggests the adopted LIDs can be significantly reduced the effects of flooding problems in the town.

Abstract 13614: Why the Pulmonary Veins: Linking Atrial 4D Flow MRI Derived Biomechanics and Pulmonary Vein Electrical Remodeling

Introduction: Pulmonary veins (PV) often trigger atrial fibrillation (AF). However, the underlying mechanism is not completely understood and predicting who benefits from PV isolation (PVI) is imprecise. We propose that arrhythmogenic PV remodeling may be related to myocardial mechanical function. Flow-encoded cardiac magnetic resonance imaging (4D Flow MRI) based computational modeling enables assessment of left atrial (LA) hemodynamics and biomechanics. In this pilot study, 4D Flow MRI derived parameters were compared to invasive electroanatomic mapping (EAM) and hemodynamics to explore potential non-invasive evaluation of PV remodeling and arrhythmogenicity. Methods: Patients (5 female, 4 male, age 64±6.7 years) with paroxysmal or early persistent AF scheduled for PVI were enrolled. All patients underwent 4D Flow MRI prior to ablation (in sinus rhythm) and intraprocedural EAM (Carto) with atrial pacing under baseline conditions and after increasing LA pressure with a fluid bolus. Non-invasive measures included peak and average velocity (m/s) and net flow (ml/cycle) in each vein (n=36) and averaged for each patient. Apparent conduction velocities in the proximal, mid and distal portions of each vein were calculated under baseline and stretch conditions from EAM. Change in LA pressure per volume bolus, a measure of atrial stiffness, was compared to non-invasive parameters. Results: In patients with LA stiffness greater than median, peak velocities (0.77±0.12 vs. 0.62±0.24 m/s, p=0.26) and net flows were higher (17±2.0 vs. 14.0±2.4 ml/cycle, p=0.06). Patients with paroxysms of spontaneous arrhythmias during mapping had higher LA stiffness (11.5±5.7 vs. 7.6±5.3 mmHg/L, p=0.30). There was a significant correlation between non-invasive average velocity and apparent conduction velocity in the proximal portion of the vein (R=-0.36, p=0.03) and the suggestion of a correlation between increasing peak flow velocity and decreased apparent conduction velocity under stretch conditions compared to baseline (R=-0.24, p=0.16). Conclusions: Our findings may indicate a link between atrial hemodynamics, electrical remodeling and PV arrhythmogenicity. Additional studies are warranted to confirm and better define these findings.

Calibration-free approach to reactive real-time control of stormwater storages

Stormwater systems will likely require major upgrades due to increases in peak flows caused by the combined effects of urbanization, densification (urban infill) and climate change. Recently, the real-time control (RTC) of storages has been considered as a means to reduce peak flows and potentially avoid major infrastructure upgrades. This paper introduces a RTC approach, the Target Flow Control (TFC) approach, which is able to maintain system outflows at or below specified target flows (e.g., existing system capacity). The key features of the approach are that it does not require calibration to catchment specific data, as is the case for existing approaches and is only based on storage level information measured in real-time during rainfall events. This makes the approach generally applicable to different catchments and able to respond to future changes in rainfall due to land use and/or climate change. The TFC approach is tested on a simple two-storage system for 750 design rainfall events from a range of climates, event durations, rainfall intensities and temporal patterns using a practically achievable control time step of 30 s. Results show that the TFC approach can achieve the desired target flows effectively, with 95% of the experiments having less than 10% errors in target flows. This is an exciting achievement, given the TFC approach does not require calibration and only requires measurable storage level information. The outcomes highlight the potential of the TFC approach as a practical RTC approach that can maximize the effectiveness of existing stormwater conveyance systems by maintaining stormwater system outflows at desired target flows, thereby potentially avoiding stormwater infrastructure upgrades due to land use and climate change.

Increasing Peak Flow of Snyder Synthetic Hydrograph Units in the Serenan Sub-Watershed of Bengawan Solo Watershed

&lt;p&gt;Changes in land use are closely related to the increasing number of people who are increasing from time to time. This land use change has an impact on increasing the runoff coefficient because the rain that falls will not be retained or seep and flows directly into the river. This is what causes an increase in peak discharge in a watershed. The purpose of this study was to determine the magnitude of changes in peak discharge that occurred in the Serenan watershed in 2015 and 2021 due to changes in land use. The method used in analyzing the peak discharge is the Snyder unit hydrograph, the results of this method will be compared with the measured unit hydrograph to determine the correlation between the two. To make a synthetic unit hydrograph, non-physical parameters are needed in the form of Ct and Cp values. The Ct value used in 2015 was 2.30 and in 2021 it was 2.00 while the Cp value in 2015 was 0.90 and in 2021 it was 1.10. The results of the analysis using the Snyder method showed that the peak discharge was 139.61 m3/s in 2015 and 194.56 m3/s in 2021. The analysis shows that the peak discharge increased by 54.95 m3/s and has a very strong correlation with the hydrograph of the measured unit. &lt;/p&gt;

Impacts of wetland loss and fragmentation on the hydrology of Zimbabwe's highveld

Abstract Wetland loss and fragmentation are among the greatest threats to water resources in developed and developing countries. While several studies on wetland fragmentation have been done, a few have looked at impacts of wetland fragmentation on hydrology, with none having been done on Zimbabwe's highveld headwater catchments. There is a critical need to investigate the influence of wetlands on flow regimes of highveld headwater catchments, to understand the hydrological role that wetlands play in sustaining water resources. Endowed with dambos, marshes and riverine wetlands, Zimbabwe's highveld play a significant role in sustaining Zimbabwe's water resources, with major river systems originating from the highveld plateau, having wetlands as their source regions. Hydrologic impacts of wetland fragmentation on flow regimes of highveld headwater catchments i.e., Upper Manyame (Manyame catchment), Nyagui (Mazowe catchment) and Macheke (Save catchment) were analyzed for the period from 1984–2021. Analysis of landcover and wetland change as well as streamflow characteristics was done for 1984, 1994, 2004, 2014 and 2021 periods. Simulation of streamflow under wetland fragmentation was done using the topographically driven rainfall-runoff model (TOPMODEL), which was set up, calibrated and validated for the most sensitive parameters, which include scaling parameter (m), transmissivity (To) and root zone available water capacity (SRmax). Results from landuse/cover analysis for the period between 1984 and 2021 showed a decrease in wetland area, followed by an increase in built up area and bare land for the same period, owing to expansion of urban areas and cultivation into wetland areas. Hydrological simulation by TOPMODEL and flow duration curve analysis show that wetland fragmentation has resulted in increased peak flows, while low flows have declined for the three catchments. The findings of this research would be helpful in understanding the hydrological functions of highveld wetlands, providing the reference for protection and sustainable utilization of wetland resources in the highveld catchments.

Effects of urbanization on stream flow, sediment, and phosphorous regime

Urbanization, if not properly managed, can lead to stream channel degradation termed Urban Stream Syndrome (USS). However, the effects of different levels of urbanization and thresholds for degradation are not well understood. The USS is characterized by increased frequency and magnitude of flood flows, increased rates of channel erosion, and degradation of aquatic habitat. In this study, changes over time in Flow Duration Curves (FDC) and Sediment Rating Curves (SRC) and resulting changes in sediment and phosphorus loads in watersheds undergoing various levels of urbanization were examined as candidate indices for detecting the presence of USS. We observed that watersheds undergoing urbanization show substantial shifts in the FDC, causing a notable increase over the whole range of stream flows and tilt in the SRC, raising the exponent and decreasing the scalar coefficient. The scalar coefficient in the SRC correlates with the percentage of the catchment area with exposed soils available for erosion, which decreases notably due to urbanization, and the exponent of the SRC increases in concert with increases in impervious cover. Changes in the exponent of the SRC associated with increased urbanization in the watershed, provide an additional diagnostic tool for identification of watercourses prone to developing urban stream syndrome. The combined effects of increased peak flows and the increase in the exponent of the SRC magnify the contribution of flood flows to the annual sediment and phosphorous loads in urbanizing watersheds. The study findings support the hypothesis that destabilized stream channels subjected to USS from increased stormflow have a significant non-point source of sediments and phosphorus from within the stream corridor in addition to off-channel upland urban area sources.