| 1. |
- Kalantari, Zahra, et al.
(författare)
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A method for mapping flood hazard along roads
- 2014
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Ingår i: Journal of Environmental Management. - : Elsevier BV. - 0301-4797 .- 1095-8630. ; 133, s. 69-77
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Tidskriftsartikel (refereegranskat)abstract
- A method was developed for estimating and mapping flood hazard probability along roads using road and catchment characteristics as physical catchment descriptors (PCDs). The method uses a Geographic Information System (GIS) to derive candidate PCDs and then identifies those PCDs that significantly predict road flooding using a statistical modelling approach. The method thus allows flood hazards to be estimated and also provides insights into the relative roles of landscape characteristics in determining road-related flood hazards. The method was applied to an area in western Sweden where severe road flooding had occurred during an intense rain event as a case study to demonstrate its utility. The results suggest that for this case study area three categories of PCDs are useful for prediction of critical spots prone to flooding along roads: i) topography, ii) soil type, and iii) land use. The main drivers among the PCDs considered were a topographical wetness index, road density in the catchment, soil properties in the catchment (mainly the amount of gravel substrate) and local channel slope at the site of a roadstream intersection. These can be proposed as strong indicators for predicting the flood probability in ungauged river basins in this region, but some care is needed in generalising the case study results other potential factors are also likely to influence the flood hazard probability. Overall, the method proposed represents a straightforward and consistent way to estimate flooding hazards to inform both the planning of future roadways and the maintenance of existing roadways.
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| 2. |
- Kalantari, Zahra
(författare)
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Adaptation of road drainage structures to climate change
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Climate change is expected to lead to more frequent extreme precipitation events, floods and changes in frost/thawing cycles. The frequency of road closures and other incidents such as flooding, landslides and roads being washed away will probably increase. Stronger demands will be placed on the function of road drainage systems. The overall aim of this thesis was to produce scientifically well-founded suggestions on adaptation of road drainage systems to climate change involving more frequent floods. The work began by examining current practice for road drainage systems in Sweden and gathering experience from professionals working with various problems concerning surface and subsurface drainage systems. Various hydrological models were then used to calculate the runoff from a catchment adjacent to a road and estimate changes in peak discharge and total runoff resulting from simulated land use measures. According to these survey and hydrological modelling studies, adaptation of road drainage systems to climate change can be grouped into two categories: i) institutional adaptation; and ii) technical adaptation. The main approaches in institutional adaptation are to: i) raise the awareness of expected climate change and its impact on drainage systems in transport administration and relevant stakeholders; ii) include adaptation measures in the existing funding programme of the transport administration; and iii) develop an evaluation tool and action plans concerning existing road drainage systems. Technical adaptation will involve ensuring that road constructions are adapted to more frequent extreme precipitation events and responsive to changes in activities and land use in areas adjacent to roads. Changes in climate variables will have effects on watershed hydrological responses and consequently influence the amount of runoff reaching roads. There is a great need for tools such as hydrological models to assess impacts on discharge dynamics, including peak flows. Improved communication between road managers and local actors in the forestry and agriculture sectors can be a means to reduce the impacts of, e.g., clear-cutting or badly managed farmland ditches.
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| 3. |
- Kalantari, Zahra, et al.
(författare)
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Evaluating the effects of simulated land use changes on peak discharge of a catchment adjoining a road
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The consequences of heavy rainfall and other extreme weather events are strongly influenced by land use within watersheds. The tested catchment consists of arable land, forest, living areas, and a creek which crosses a main road at the bottom of the catchment. The theoretical hydrological responses to different land use changes and four different extreme events were quantified by model simulations using MIKE-SHE. Land use composition and configuration was found to affect discharge; clear-cutting on 30% of the catchment area produced a 60% increase in peak discharge and a 10% increase in total runoff during a 50-year summer event. There were only small effects on peak discharge during smaller storms. Reforestation of 60% of basin area was the most effective measure to reduce peak flow, mainly for smaller (2-, 5- and 10-year) storms. Grassed waterways reduced water velocity in the stream and resulted in a 28% reduction in peak flow at the catchment outlet with the same 50-year event. A smaller degree of reforestation (30%) of the basin area was the most efficient measure to decrease total runoff. Hence different measures may be the most efficient for peak discharges and total runoff from the area. The specific effect of land use measures on catchment discharge depends on their spatial distribution and on the size and time of storm events.
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| 4. |
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| 5. |
- Kalantari, Zahra, et al.
(författare)
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Modeller subjectivity and calibration impacts on hydrological model applications : an event-based comparison for a road-adjacent catchment in South-East Norway
- 2015
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 502, s. 315-329
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Tidskriftsartikel (refereegranskat)abstract
- Identifying a ‘best’ performing hydrologic model in a practical sense is difficult due to the potential influences of modeller subjectivity on, for example, calibration procedure and parameter selection. This is especially true for model applications at the event scale where the prevailing catchment conditions can have a strong impact on apparent model performance and suitability. In this study, two lumped models (CoupModel and HBV) and two physically-based distributed models (LISEM and MIKE SHE) were applied to a small catchment upstream of a road in south-eastern Norway. All models were calibrated to a single event representing typical winter conditions in the region and then applied to various other winter events to investigate the potential impact of calibration period and methodology on model performance. Peak flow and event-based hydrographs were simulated differently by all models leading to differences in apparent model performance under this application. In this case-study, the lumped models appeared to be better suited for hydrological events that differed from the calibration event (i.e., events when runoff was generated from rain on non-frozen soils rather than from rain and snowmelt on frozen soil) while the more physical-based approaches appeared better suited during snowmelt and frozen soil conditions more consistent with the event-specific calibration. This was due to the combination of variations in subsurface conditions over the eight events considered, the subsequent ability of the models to represent the impact of the conditions (particularly when subsurface conditions varied greatly from the calibration event), and the different approaches adopted to calibrate the models. These results indicate that hydrologic models may not only need to be selected on a case-by-case basis but also have their performance evaluated on an application-by-application basis since how a model is applied can be equally important as inherent model structure.
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| 6. |
- Kalantari, Zahra, et al.
(författare)
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On the utilization of hydrological modelling for road drainage design under climate and land use change
- 2014
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 475, s. 97-103
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Tidskriftsartikel (refereegranskat)abstract
- Road drainage structures are often designed using methods that do not consider process-based representations of a landscape's hydrological response. This may create inadequately sized structures as coupled land cover and climate changes can lead to an amplified hydrological response. This study aims to quantify potential increases of runoff in response to future extreme rain events in a 61 km(2) catchment (40% forested) in southwest Sweden using a physically-based hydrological modelling approach. We simulate peak discharge and water level (stage) at two types of pipe bridges and one culvert, both of which are commonly used at Swedish road/stream intersections, under combined forest clear-cutting and future climate scenarios for 2050 and 2100. The frequency of changes in peak flow and water level varies with time (seasonality) and storm size. These changes indicate that the magnitude of peak flow and the runoff response are highly correlated to season rather than storm size. In all scenarios considered, the dimensions of the current culvert are insufficient to handle the increase in water level estimated using a physically-based modelling approach. It also appears that the water level at the pipe bridges changes differently depending on the size and timing of the storm events. The findings of the present study and the approach put forward should be considered when planning investigations on and maintenance for areas at risk of high water flows. In addition, the research highlights the utility of physically-based hydrological models to identify the appropriateness of road drainage structure dimensioning
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| 7. |
- Kalantari, Zahra, et al.
(författare)
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Quantifying the hydrological impact of simulated changes in land use on peak discharge in a small catchment
- 2014
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 466, s. 741-754
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Tidskriftsartikel (refereegranskat)abstract
- A physically-based, distributed hydrological model (MIKE SHE) was used to quantify overland runoff in response to four extreme rain events and four types of simulated land use measure in a catchment in Norway. The current land use in the catchment comprises arable lands, forest, urban areas and a stream that passes under a motorway at the catchment outlet. This model simulation study demonstrates how the composition and configuration of land use measures affect discharge at the catchment outlet differently in response to storms of different sizes. For example, clear-cutting on 30% of the catchment area produced a 60% increase in peak discharge and a 10% increase in total runoff resulting from a 50-year storm event in summer, but the effects on peak discharge were less pronounced during smaller storms. Reforestation of 60% of the catchment area was the most effective measure in reducing peak flows for smaller (2-, 5- and 10-year) storms. Introducing grassed waterways reduced water velocity in the stream and resulted in a 28% reduction in peak flow at the catchment outlet for the 50-year storm event. Overall, the results indicate that the specific effect of land use measures on catchment discharge depends on their spatial distribution and on the size and timing of storm events.
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| 8. |
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| 9. |
- Kalantari, Zahra, et al.
(författare)
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Road drainage in Sweden : Current practice and suggestions for adaptation to climate change
- 2013
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Ingår i: Journal of Infrastructure Systems. - 1076-0342 .- 1943-555X. ; 19:2, s. 147-156
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes current practice in road surface and subsurface drainage in Sweden and analyzes the necessity for adaptation of the planning, construction, operation, maintenance and monitoring of road drainage measures to climate change. Based on a survey of professionals working with various aspects of road drainage, the study sought to identify: (1) problems experienced concerning road drainage, focusing on the current Swedish climate; (2) future problems regarding climate change impacts such as flooding and high flows; and (3) suggestions for adaptation measures concerning road drainage systems, taking future climate change into account. Suggested improvements concerning management and planning included clarification of responsibility for drainage issues, better overview of the location and condition of drainage facilities, inclusion of drainage system maintenance in procurement of operation contracts, maintenance plans for drainage facilities, and monitoring and inspection of drainage measures. Suggestions concerning drainage system construction, operation and maintenance included increasing the capacity of drainage facilities, stabilizing ditch slopes and various measures to prevent clogging of culverts
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| 10. |
- Kalantari, Zahra, 1979-
(författare)
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Road structures under climate and land use change : Bridging the gap between science and application
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Future changes in climate and land use are likely to affect catchment hydrological responses and consequently influence the amount of runoff reaching roads. Blockages and damage to under-dimensioned infrastructure can be extremely costly for the regions affected. This study aims to produce scientifically well-founded suggestions on adaptation of road drainage systems to climate changes resulting in more frequent floods. This thesis demonstrates the need to integrate aspects of climate change and land use impacts into the planning and practice of road construction and maintenance in Sweden. Tools such as hydrological models are needed to assess impacts on discharge dynamics. Identifying a ‘best’ practically performing hydrological model is often difficult due to the potential influence of modeller subjectivity on calibration procedure, parameter selection, etc. Hydrological models may need to be selected on a case-by-case basis and have their performance evaluated on an application-by-application basis.The work presented here began by examining current practice for road drainage systems in Sweden. Various hydrological models were then used to calculate the runoff from a catchment adjacent to a road and estimate changes in peak discharge and total runoff resulting from simulated land use measures. Overall, the results indicate that the specific effect of land use measures on catchment discharge depend on their spatial distribution and on the size and timing of storm events. Scenarios comprising a changing climate up to 2050 or to 2100 and forest clear-cutting were used to determine whether the current design of road drainage construction is sufficient for future conditions. Based on the findings, the approach developed can be used for similar studies, e.g. by the Swedish Transport Administration in dimensioning future road drainage structures to provide safe and robust infrastructure.Furthermore, a statistical method was developed for estimating and mapping flood hazard probability along roads using road and catchment characteristics. The method allows flood hazards to be estimated and provides insight into the relative roles of landscape characteristics in determining road-related flood hazards. Overall, this method provides an efficient way to estimate flooding hazards and to inform the planning of future roadways and the maintenance of existing roadways.
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