Road Culverts Research Articles

Relative contributions of different local sources to riverborne microplastic in a mixed landuse area within a tropical catchment

Information on the relative contributions of microplastics coming from different sources is important to help prioritise measures to reduce river contamination levels and limit human and ecological health risks. This paper reports on work which aimed to quantitatively assess the relative concentrations and types of microplastic delivered from differed sources to a second order river. The study was undertaken in a mixed landuse area within a rapidly urbanising catchment in Malaysia. Over a six-week period, water samples were collected from road culverts and drains in residential and industrial areas across the area to assess microplastic concentrations, while inputs from atmospheric deposition and wastewater treatment plants (WWTPs) were also quantified. Microplastic fibres and fragments were the dominant material in all sources, with the majority consisting of styrene-butadiene rubber and nylon. Culverts draining main roads were the main contributor to riverborne microplastic, delivering 42.20 ± 35.29 particles/L directly to the river channel. Road inputs were up to seven times greater than those from residential (8.53 ± 9.91 particles/L) and industrial (5.67 ± 4.88 particles/L) areas. The five WWTPs had removal efficiencies of between 30.95 ± 5.51% and 69.94 ± 22.17%, with their outflows delivering microplastics to the river in concentrations similar to those in uncontrolled residential and industrial drains. Atmospheric deposition across the study area was estimated to be 76.07 ± 32.85 particles/m2/day (=8.35 ± 5.11 particles/L). Mitigation strategies in the study area should focus on improving management of water draining roads, and re-routing discharges from domestic and industrial areas to WWTPs rather than allowing them to flow directly to the river. The low efficiencies of some of the WWTPs are not unusual, and indicate the need for additional water treatment to deal with microplastic present in wastewater.

Remote sensing framework details riverscape connectivity fragmentation and fish passability in a forested landscape

Fragmentation of stream networks from anthropogenic structures such as road culverts can affect the health of a catchment by negatively affecting the ecosystem’s biota, their movements, abundance, and species richness. We present a framework using publicly available LiDAR and orthophotography to locate and identify road crossings, i.e. the most prolific of barriers in forested landscapes, and evaluate fragmentation and passability at the landscape scale. Coupling the LiDAR stream network and private road network in the 3,223 km2 study area, we identified 1,052 stream crossings of which, 32% were culverts and 12% of the total stream network was potentially inaccessible due to these culverts. We correctly identified the type of stream-road crossings at >90% of any stream order and at 100% at Orders >2. The 10 culverts restricting the most stream kilometers, restricted >34% of the potential stream habitats for four species of fish, a result that provides the resource management with a first assessment for effective improvement of connectivity across this landscape. With this framework, managers equipped with appropriate imagery can create a stream crossing database with minimal funding, create an inventory of instream barriers, and prioritize removals at a landscape-scale, thus providing an effective assessment and decision-making tool for their habitat restoration efforts.

A Comparison of Brook Trout Passage at Road Culverts to Broadscale Assessment Criteria in a Pennsylvania Headwater Stream

AbstractRestoring stream connectivity by replacing road culverts is a high conservation priority, yet long‐term fish passage data aimed to “ground‐truth” culvert prioritization methods are lacking. One common tool for prioritizing culvert removals is the protocol developed by the North Atlantic Aquatic Connectivity Collaborative (NAACC), which uses culvert characteristics to estimate barrier severity and fish passage. To determine the degree to which NAACC scoring reflects trout passage, we monitored Brook Trout Salvelinus fontinalis movements through three culverts and a reference site (no culvert) in a central Pennsylvania watershed. Passage was nearly continuously monitored for 16 months using remote stationary PIT tag readers. We found that NAACC ranks underestimated Brook Trout passage through two of three culverts. Specifically, the culvert with a rank of “reduced aquatic organism passage (AOP)” experienced higher rates of upstream passage (up to 10 upstream movements per day) than all other sites combined, including the reference site. The reduced AOP site also had a similar proportion of the tagged population that moved upstream (20.9%) compared to the reference site (16.9%). Of the two remaining culverts, both box culverts rated as “no AOP,” one had almost no upstream passage (only two upstream movements over the entire study) and the other had passage rates similar to the reference stream (up to four upstream movements per day). Brook Trout tended to move during high flow and the fall spawning period. We suggest that, for the streams considered in our study, the NAACC protocol may better predict upstream passage if it emphasizes culvert type and adjusts measurement thresholds in the AOP coarse screening. If these patterns are supported by studies at other locations, a more nuanced treatment of culvert type and outlet characteristics in NAACC protocols may more accurately predict Brook Trout passage through culverts.

Automated calculation of road reinforced con-crete round culverts for operation in free-flow mode in program UKRRVS21

The modern approach to the design of road culverts involves the use of computeraided design (CAD). In design organizations of Ukraine software products of the Minsk company CREDO are being used for calculations of capacity of culverts by GRIS_T. Since 2019, the UKRRVS program is being developed to calculate culverts of road structures according to Ukrainian standards. At the moment, the program has the calculation of stormwater runoff according to MADI/SoyuzDorProekt formula and meltwater runoff (according the Road Handbook). In 2020, a new stage of automated calculation of road culverts started - calculations of capacity. The article presents the automated calculation of road reinforced concrete round culverts for pressureless operation. Goal. It is proposed to automate the calculation of road reinforced concrete round culverts for pressureless oper-ation. Methodology. The current methods for calculating the throughput of reinforced concrete road culverts have been used. Programming was carried out in the C# language using object-oriented programming. Results. The state of affairs in the auto-mation of hydraulic calculations in the road industry in accordance with Ukrainian standards was analyzed. It was concluded that at the moment the production uses the GRIS program of the CREDO company. The UKRRVS program is being developed. In this program, the issue of automating the calculation of the throughput of round culverts for operation in freeflow mode is relevant. The question of the methodology and algorithmization of this calculation, coding and interface support has been resolved. Practical value. The algorithm for calculating road culverts has been developed. A part of calculating the throughput of road culverts has been created in the UKRRVS program. This part covers the most com-mon group - round reinforced concrete culverts for freeflow operation. Originality. The interface has been created for the automation program for calculating road culverts. When you click the button “Round reinforced concrete pipes” in the main menu of the program UKRVS 21, the window “Calculation of a round reinforced concrete pipe operating in pressureless mode” opens. The calculation consists of three parts: the area of formation of initial data, the button “Calculate”, and the area of output of results of calculations. The area of formation of ini-tial data consists of 7 points. The area of the results of calculation of round reinforced concrete road cul-verts working in a pressureless mode consists of 14 points.

What evidence exists on the impacts of flow variability on fish and macroinvertebrates of temperate floodplain rivers in Central and Western Europe? A systematic map protocol

BackgroundFlow variability is considered a fundamental factor affecting riverine biota. Any alterations to flow regime can influence freshwater organisms, and this process is expected to change with the projected climate change. This systematic map, therefore, aims at investigating the impacts of natural (resulting from climatic variability), anthropogenic (resulting from direct human pressure), and climate change-induced flow variability on fish and macroinvertebrates of temperate floodplain rivers in Central and Western Europe. Particular focus will be placed on the effects of extreme low and high discharges. These rare events are known to regulate population size and taxonomic diversity.MethodsAll studies investigating the effects of flow variability on metrics concerning freshwater fish and macroinvertebrates will be considered in the map, particularly metrics such as: abundance, density, diversity, growth, migration, recruitment, reproduction, survival, or their substitutes, such as biomonitoring indices. Relevant flow variability will reflect (1) anthropogenic causes: dams, reservoirs, hydroelectric facilities, locks, levees, water abstraction, water diversion, land-use changes, road culverts; (2) natural causes: floods, droughts, seasonal changes; or (3) climate change. Geographically, the map will cover the ecoregion of Central and Western Europe, focusing on its major habitat type, namely “temperate floodplain rivers and wetlands”. The review will employ search engines and specialist websites, and cover primary and grey literature. No date, language, or document type restrictions will be applied in the search strategy. We expect the results to be primarily in English, although evidence (meeting all eligibility criteria) from other languages within the study area will also be included. We will also contact relevant stakeholders and announce an open call for additional information. Eligibility screening will be conducted at two levels: title and abstract, and full text. From eligible studies the following information will be extracted: the cause of flow variability, location, type of study, outcomes, etc. A searchable database containing extracted data will be developed and provided as supplementary material to the map report. The final narrative will describe the quantity and key characteristics of the available evidence, and identify knowledge gaps and knowledge clusters, i.e. subtopics sufficiently covered by existing studies allowing full systematic review and meta-analysis.

Mountain Road-Culvert Maintenance Algorithm

The objective of this research was to determine the probability of road overtopping occurrence for a road culvert caused by surface runoff from the upstream catchment. A hydrological–hydraulic model was used for the development of an algorithm for road culvert maintenance based on the overtopping occurrence probability (CMOOP algorithm) for small mountain catchments. The hydrological model defines the regression dependence between the runoff hydrograph peak values and the probability of occurrences, whereas the hydraulic model calculates the culvert flow capacity by including in the calculation the level of sediment that culvert is filled with. The relationship between occurrences of overtopping and peak runoff value was defined using the runoff hydrograph transformation model in the accumulation on the upstream side of the road. In addition to the calculation of overtopping occurrence probability for the existing culvert condition, the CMOOP algorithm was used to analyze the impact of rehabilitation and reconstruction works from the perspective of legally based safety criterion for road overtopping occurrence probability (SCROOP). The CMOOP algorithm was appled to 67 concrete culverts located in a mountain road section in the Republic of Serbia. The results show that the application of rehabilitation works on selected culverts will increase the percentage of culverts that satisfy SCROOP from 49.25% to 89.55%, which confirms that the accumulated stone sediment is the main reason for the SCROOP unfulfillment.

Spatio-Temporal Assessment of the Performance of March to May 2020 Long Rains and Its Socio-Economic Implications in Northern Coast of Tanzania

The spatio-temporal analysis of the performance of the March to May (MAM) 2020 rainfall and its societal implications to Northern Coastal Tanzania (NCT) including Zanzibar was investigated. The uniqueness of the October to December, 2019 (OND) rainfall and the extension of the January to February, 2020 rainfall in Zanzibar which coincided with MAM 2020 rainfall was among the issues which prolonged MAM 2020 rainfall in NCT and Zanzibar. The National Center for Environmental Prediction (NCEP) in collaboration with National Center for Atmospheric Research (NCAR). Reanalysis 1 datasets of u (zonal) and v (meridional) winds, sea surface temperatures anomalies, relative humidity, amount of precipitable water and ocean net flux were analyzed. Other datasets include the Tanzania Meteorological Authority (TMA) observed rainfall records, maximum and minimum temperatures. Moreover, TMA and Intergovernmental Climate Prediction and Analysis Center (ICPAC). MAM 2020 rainfall and temperature forecast reports were interpreted. Gridded and observed datasets were calculated into monthly and seasonal averages. As for observed data, long-term monthly and MAM percentage changes were calculated. Besides, the correlation between rainfall anomalies with an area-averaged SSTA for defined regions and stations in Zanzibar was performed. Lastly, the calculated monthly and seasonal rainfall was compared to MAM periods of 2016, 2017, 2018 and 2019. Results revealed that consecutive five MAM seasonal rainfall was among the highest ones in records with that of 2020 being exceptional. These MAM seasons had percentage contribution ranged from 68% - 212%, 150% - 304%, 22% - 163% and 57% - 170% for stations in Zanzibar and 130% - 230%, 57% - 168% and 230% - 706% for NCT station, respectively. Compared to previous MAM seasons of 2016-2019, MAM 2020 rainfall season was spatially well distributed in our study area with rainfall ranging from 1200 to 2100 mm and up to 900 in most Zanzibar and NCT stations. Indeed, the study revealed that the observed highest rainfall and flooding was enhanced by wet seasons of MAM 2019, OND 2019 and DFJ (2019-2020). Other dynamics which accelerated MAM 2020 rainfall were the higher SSTA ranged from 0.5°C - 1.5°C and 1.5°C - 2.5°C over Southwestern Indian Ocean (SWIO) and coastal Tanzania and the increased trend of area-averaged SSTA on various SWIO blocks. Besides, parameters including Rhum, PWR and wind regimes were supporting the MAM 2020 rainfall. The socio-economic implications of these rains were strong and spatially well distributed in Zanzibar. For instance, a death toll of about 10 people, a great number of road culverts were washed away, and about 3600 houses were fallen or damaged, leading to a significant number of homeless people. As for NCT, the catastrophes include loss of lives, increased water levels over Lake Victoria leading to flooded islands and re allocation of more than 1000 people. In Kenya, more than 116 people died and 40,000 people were displaced. Conclusively, the study has shown the uniqueness (i.e., strength and societal implications) of MAM 2020 compared to other seasons; hence more studies on understanding the factors affecting extreme rainfall seasons in East Africa are required.

Low light intensities increase avoidance behaviour of diurnal fish species: implications for use of road culverts by fish.

Inadequately designed culverts can be physical barriers to fish passage if they increase the velocity of water flow in the environment, alter natural turbulence patterns or fail to provide adequate water depth. They may also act as behavioural barriers to fish passage if they affect the willingness of fish species to enter or pass through the structure due to altered ambient light conditions. To understand how reduced light intensity might affect fish behaviour in culverts, the authors performed a behavioural choice experiment quantifying the amount of time individual fish spent in dark and illuminated areas of a controlled experimental channel. They found that behavioural responses were largely reflective of the species' diel activity patterns; the diurnal species Craterocephalus stercusmuscarum and Retropinna semoni preferred illuminated regions, whereas the nocturnal/crepuscular Macquaria novemaculeata preferred the darkened region of the channel. Bidyanus bidyanus were strongly rheotactic, and their behaviour was influenced more by water flow direction than ambient light level. The authors then determined that a threshold light intensity of only c. 100-200 lx (cf. midday sunlight c. 100,000 lx) was required to overcome the behavioural barrier in c. 70% of the diurnally active C. stercusmuscarum and R. semoni tested. When these values were placed into an environmental context, 15 road-crossing (3.4-7.0 m long) box (c. 1 m × 1 m, height × width) and pipe (c. 1 m diameter) culverts sampled in Brisbane, Australia, recorded light intensities in the centre of the structure that were below the threshold for C. stercusmuscarum and R. semoni movement and could potentially be a barrier to their passage through the structure. Attention is required to better understand the impacts of low light intensity in culverts on fish passage and to prioritize restoration.

Small instream infrastructure: Comparative methods and evidence of environmental and ecological responses

Abstract1. Around the globe, instream infrastructures such as dams, weirs, and culverts associated with roads are wide‐spread and continue to be constructed. There is limited documentation of smaller infrastructure because of mixed regulation and laws related to instream construction, as well as difficulty in documentation because of their size and frequency in waterscapes.2. We reviewed evidence of different methods used to quantify environmental and ecological responses (positive, negative, or neutral) to dams, weirs, and culverts.3. Most studies (78% of 87) in our review evaluated dams or weirs, and more than half evaluated environmental or ecological responses at more than one of these structures. More than half of the studies used spatial (disturbed–undisturbed in the same or a different catchment) rather than temporal (before–after construction or before–after destruction) comparative methods. Evaluations also tended to focus on ecological variables, most specifically on fish community responses (just over a quarter) to infrastructure.4. More than half (58%) of the evaluations at dams, weirs, or culverts reported negative environmental or ecological responses. Discrepancies in responses recorded for different infrastructure types could be partially explained by the focus on ecological responses in reviewed studies and related metrics used for evaluations (e.g. biotic groups, richness, and abundance), the imbalance of studies at different infrastructure types, and discrepancies in spatial and temporal scales of evaluations compared to those at which the variables respond to infrastructure.5. Despite the abundance of road culverts greatly exceeding the number of small or large dams worldwide, they were evaluated in only 22% of studies that we reviewed. Our findings underscore the need for studies to not only better understand local but also cumulative impacts of these smaller infrastructure, as these could be greater than those caused by large infrastructure depending on their location, density, and type, among other factors. Such studies are needed to inform infrastructure planning and watershed management.

Effects of transportation infrastructure on fishes in the Ozark and Ouachita Mountains

Rivers worldwide are fragmented by transportation infrastructure that blocks the movements of aquatic organisms. To assess the effects of road culverts on stream fishes in the Ozark and Ouachita Mountains regions of Oklahoma, we surveyed 39 free-flowing sites, 29 sites upstream and 29 sites downstream of culverts. We observed differences in species richness and abundance between free-flowing sites, sites upstream of a culvert, and downstream sites. We also found that the degree to which a culvert affected richness and abundance depended on culvert type and length. Furthermore, the culverts in the poorest condition had the greatest effects on abundance and richness. Replacement of these poor condition culverts is likely a high priority for both conservation groups and infrastructure agencies. Our findings enable conservation practitioners to identify structures that may be high priorities for aquatic organism passage projects, including those that may benefit from cost-sharing or collaboration with infrastructure agencies.

Monthly suspended-sediment apportionment for a western Lake Erie agricultural tributary

Black Creek, a headwater to the Maumee River and western Lake Erie, is an agricultural basin with a mix of cropland (66%), pasture (19%), and forest (7%) linked by a road network to the rural community. Suspended sediment was collected monthly during the 2018 water year for the main stem and two sub-basins using in-situ, passive samplers that integrated a range of streamflow conditions. Sediment fingerprinting used 44 indicators to apportion samples among five sources: cropland, pasture, forest, road dirt, and streambanks. Cropland, pasture, and streambanks had similar ranges in sediment-bound phosphorus (679–1670 ppm). Cropland contributed 21 ± 15% (monthly mean ± standard deviation; 0–46% among individual months) of suspended sediment during the year. Fall and spring peaks in cropland contribution highlight the ongoing importance of on-field management, but this small contribution of suspended sediment relative to the expanse of cropland may reflect implementation of best-management practices. Pasture contributed 0–66% (16 ± 19%) of suspended sediment and roads 0–26% (6 ± 6%). Streambanks contributed 12–100% (55 ± 25%) and was the only source identified in all sediment samples. In this basin, most cropland-adjacent streambanks are protected by a riparian setback. However, streams traversing other land-use types are not as consistently protected, and these setbacks do not protect the stream channel from discharge of water from sump pumps, road culverts, or tile drains. The contribution of sediment from other land uses combined with that from the agricultural drainage network (as streambank material) underscores the need to consider water movement in the basin as a whole.

Assessment of storm direct runoff and peak flow rates using improved SCS-CN models for selected forested watersheds in the Southeastern United States

Study regionSoutheastern United States Study focusThe objective was to evaluate the ability of two modified SCS-CN models to predict direct runoff (DRO) and peak discharge rate (Qp) for selected storm events in three forested watersheds in the region - one low-gradient system in South Carolina, two high-gradient upland systems in North Carolina, and a mid-gradient upland system in Arkansas. New hydrological insights for the regionThe calculated peak discharge rate Qp values by all methods were unsatisfactory when using the default pond and swamp adjustment factor (Fp) value of 0.72 recommended in the SCS TR55 guideline, indicating that use of the default Fp value may result in erroneous Qp estimates for forest watersheds with high retention capacities. These findings, indicating the superiority of the modified Sahu-Mishra-Eldo (SME_m) method to the original SCS method in runoff calculations and substantially lower Fp values in the associated Qp method, are significant for hydrologists and engineers who frequently apply the methods in design of storm water management structures including road culverts on forested landscapes.

Durability and modern technologies of strengthening culverts and animal crossings

The paper discusses selected issues regarding to repair and reinforcing methods of the of culverts and animal crossing structures. Information was also provided on materials used for construction, and renovation of culverts. In addition, the paper discusses the most commonly used technologies of reinforcing and reconstructing these objects. Particular attention has been paid to the ways of selecting the reinforcement method and systems, taking into account the properties of the materials used in the renovation of these structures. In addition, the paper, according to the author, arranges also issues related to the proper performance of renovation for road culverts.

Genetic Assignment of Brook Trout Reveals Rapid Success of Culvert Restoration in Headwater Streams

AbstractFragmentation of aquatic habitats is a global conservation concern. Losses of both biodiversity and genetic diversity have been attributed to this phenomenon as dispersal movements between habitat patches are restricted. Brook Trout Salvelinus fontinalis in the upper Shavers Fork watershed of West Virginia exhibit high dispersal rates and lengthy dispersal distances; however, road culverts have been hypothesized to influence the movement of Brook Trout between tributaries. Removing impassable culverts could serve as a tool to facilitate movements into previously isolated streams. We classified the passability of road culverts by their physical attributes and collected samples above each structure as well as in two streams without culverts to test for genetic population differentiation attributed to culverts. After we determined that the majority of streams consisted of a single genetic population, with the exception of two streams containing culverts designated as impassable (Beaver Creek and Lamothe Hollow), the culvert structures were restored to eliminate outlets perched above the stream bottom and were subsequently resampled 1 year after project completion. Although no individuals were assigned as first‐generation migrants into either Beaver Creek or Lamothe Hollow before culvert restoration, five individuals were detected as first‐generation migrants into Beaver Creek (13%), and one individual was identified as a first‐generation migrant into Lamothe Hollow (4.5%) after culvert restoration. Three different streams were found to be sources of the migrants into Beaver Creek, and the single individual migrating into Lamothe Hollow was from a fourth source stream. The identification of first‐generation migrants through genetic assignment not only provides a tool with which to test the effectiveness of barrier removal and subsequent restoration success but also to support the importance of culvert replacement in headwater streams.

LABORATORY EVALUATION ON PERFORMANCE OF GLASS FIBER REINFORCED PLASTIC MORTAR PIPE CULVERTS

This paper investigated the performance and behaviour of glass fiber reinforced plastic mortar (FRPM) pipes under different loading conditions. FRPM pipes with inner diameter of 1500 mm were prefabricated in factory. Mechanics performance testing (ring and axial compressive strength and elastic modulus), stiffness and fatigue test were carried out in laboratory. Ring stiffness test provided pipe stiffness (PS) which is a function of geometry and material type of pipe through parallel plate loading test (PPLT). The fatigue test and micro-structure measure method were used to evaluate the durability effects of FRPM under repeated compression load. Results indicated that FRPM pipes had better mechanic performances as the road culverts under soils. It may be helpful for the design and construction of FRPM culverts.

Conserving rare species can have high opportunity costs for common species.

Conservation practitioners face difficult choices in apportioning limited resources between rare species (to ensure their existence) and common species (to ensure their abundance and ecosystem contributions). We quantified the opportunity costs of conserving rare species of migratory fishes in the context of removing dams and retrofitting road culverts across 1,883 tributaries of the North American Great Lakes. Our optimization models show that maximizing total habitat gains across species can be very efficient in terms of benefits achieved per dollar spent, but disproportionately benefits common species. Conservation approaches that target rare species, or that ensure some benefits for every species (i.e., complementarity) enable strategic allocation of resources among species but reduce aggregate habitat gains. Thus, small habitat gains for the rarest species necessarily come at the expense of more than 20 times as much habitat for common ones. These opportunity costs are likely to occur in many ecosystems because range limits and conservation costs often vary widely among species. Given that common species worldwide are declining more rapidly than rare ones within major taxa, our findings provide incentive for triage among multiple worthy conservation targets.

Aligning dam removals and road culvert upgrades boosts conservation return-on-investment

Dams and road culverts fragment river ecosystems worldwide by restricting the movement of aquatic species. In many watersheds, a diverse set of actors coordinates the removal of these barriers. Non-governmental organizations often focus on small dams and road culverts, while large dam removal projects are coordinated by federal agencies or coalitions of partners. Here we evaluate the return-on-investment of these strategies by exploring a continuum of methods for selecting barrier removal projects, ranging from a focus on many small barrier removal projects to a few large ones. We used estimated removal costs of more than 100,000 barriers in the North American Great Lakes to construct economically realistic barrier removal scenarios. We then simulated the movement of stream-resident and anadromous fishes through model river networks with a few large dam removals, many road culvert retrofits, or a mix of both. We found that the strategy of removing both dams and road culverts had the greatest potential to benefit both stream-resident and anadromous fishes, but only when projects were aligned longitudinally within the river network. Our results demonstrate the importance of allocating conservation resources to both small and large restoration projects, and highlight a need for increased coordination and communication among the many different organizations investing in barrier removals. Our findings complement optimization approaches to prioritizing barrier removals by providing general guidelines for practitioners to follow when project selection must depart from a prescribed portfolio of projects.

Evaluating preprocessing methods of digital elevation models for hydrological modelling

AbstractWith the introduction of high‐resolution digital elevation models, it is possible to use digital terrain analysis to extract small streams. In order to map streams correctly, it is necessary to remove errors and artificial sinks in the digital elevation models. This step is known as preprocessing and will allow water to move across a digital landscape. However, new challenges are introduced with increasing resolution because the effect of anthropogenic artefacts such as road embankments and bridges increases with increased resolution. These are problematic during the preprocessing step because they are elevated above the surrounding landscape and act as artificial dams. The aims of this study were to evaluate the effect of different preprocessing methods such as breaching and filling on digital elevation models with different resolutions (2, 4, 8, and 16 m) and to evaluate which preprocessing methods most accurately route water across road impoundments at actual culvert locations. A unique dataset with over 30,000 field‐mapped road culverts was used to assess the accuracy of stream networks derived from digital elevation models using different preprocessing methods. Our results showed that the accuracy of stream networks increases with increasing resolution. Breaching created the most accurate stream networks on all resolutions, whereas filling was the least accurate. Burning streams from the topographic map across roads from the topographic map increased the accuracy for all methods and resolutions. In addition, the impact in terms of change in area and absolute volume between original and preprocessed digital elevation models was smaller for breaching than for filling. With the appropriate methods, it is possible to extract accurate stream networks from high‐resolution digital elevation models with extensive road networks, thus providing forest managers with stream networks that can be used when planning operations in wet areas or areas near streams to prevent rutting, sediment transport, and mercury export.

What are the impacts of flow regime changes on fish productivity in temperate regions? A systematic map protocol

BackgroundEcosystem changes from altered flows can have multiple impacts on fish, including changes to physical habitat, habitat access, food supplies, behaviour, community composition, energy expenditure, and population dynamics. There is growing evidence of the potential negative consequences of altered flow regimes on fluvial ecosystems and the fisheries they support. As such, the scientific and policy communities have acknowledged the need for maintaining or restoring natural flow variability in order to sustain ecological health of fluvial ecosystems. However, for resource managers, making decisions on the potential effects of flow alterations on fish productivity has been problematic because there are still uncertainties regarding flow-fish productivity relationships. Therefore, to ensure the maintenance of healthy and productive aquatic ecosystems and the sustainability of riverine fisheries, a better understanding of the impacts of flow alteration on fish productivity is needed. Due to the wide scope of this review, and the diversity of fish productivity outcomes used to evaluate flow alteration impacts, the set of studies will be quite heterogeneous. Therefore, prior to undertaking a comprehensive and quantitative synthesis, we propose to begin with a systematic map to provide an overview of the available evidence on the impacts of flow regime changes on fish productivity. We will also use this systematic map to identify subtopics that are sufficiently covered by existing studies to allow full systematic reviewing.MethodsThis systematic map will compile evidence on the impacts of flow regime changes on fish productivity. All studies that evaluate the effects of flow regime change on direct outcomes of fish productivity, will be included in the review. We will use a broad definition of fish productivity to include any measurement related to: biomass, abundance, density, yield, diversity, growth, survival, individual performance, migration, reproduction, recruitment, or surrogate thereof. Relevant causes of a change in/modification to flow regime can include: (1) anthropogenic causes: dams, reservoirs (impoundments), hydroelectric facilities, locks, levees, water withdrawal (abstraction), water diversion, land-use changes, and road culverts; or (2) natural causes: climate change (possible indirect anthropogenic cause as well), floods, droughts, seasonal changes. Any freshwater or estuarine fish species or species groups in temperate regions will be considered. The review will include a wide range of sources including primary and grey literature and use public databases, search engines and specialist websites. A searchable database containing extracted meta-data from relevant included studies will be developed and provided as a supplementary file to the map report. The final narrative will describe the quantity and key characteristics of the available evidence, identify knowledge gaps for future research and identify subtopics that are sufficiently covered by existing studies to allow full systematic reviewing.

Low light inhibits native fish movement through a vertical‐slot fishway: Implications for engineering design

AbstractLight intensity within a vertical‐slot fishway was manipulated to determine the effect on fish movement. Three treatments (darkness, low light, artificial light) were tested with natural daylight used as a control. Light intensity varied from 0 to 1,692 lux for the three treatments and from 1 to 4,550 lux for the control. Light intensity outside the fishway ranged from 31 to 80 900 lux. A total of 64 385 fish were collected from six species. The abundance of Australian smelt Retropinna semoni (Webber), unspecked hardyhead Craterocephalus stercusmuscarum fulvus Ivantsoff, Crowley and Allen, bony herring Nematalosa erebi (Günther), carp gudgeon Hypseleotris spp. and Eastern gambusia Gambusia holbrooki (Girard) moving upstream reduced significantly under low‐light conditions. Conversely, movement of macroinvertebrates (freshwater shrimp Macrobrachium australiense Holthuis and freshwater prawn Paratya australiensis Kemp) increased at low‐light intensities. The number of fish moving under artificial light (28 617) was similar to that under natural daylight (33 919). Movements of Australian freshwater fish and macroinvertebrates were found to be influenced by changes in light intensity. Instream structures that alter light conditions, such as road culverts, may thus act as behavioural barriers to fish movement, and this could be mitigated by the provision of natural or artificial light.