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An introduction to articles in the issue is presented on topics including the effectiveness of a potential pier-type ice-control structure as a long-term remediation option to address a problem of potential release of polychlorinated biphenyls (PCBs) from the Grasse River, New York, the planning and design of a bridge in an ice-affected river, and different ice processes in two different culvert structures incorporating fish-passage design.

Bridge infrastructure assets should be planned, designed, constructed, and operated to account for the physical processes that may occur over their service lives. In ice-affected rivers, this includes the interaction of bridge infrastructure with river ice. Advancements in river-ice science and modelling of ice processes in ice-covered rivers have enhanced the abilities of civil/hydrotechnical engineers to plan, design, and construct bridges in and along rivers with seasonal ice covers. In this paper, an overview is presented of ice-related considerations with respect to bridges. The bottom-chord elevation of the bridge superstructure with respect to water and ice levels, pier design to withstand ice forces, the waterway opening for ice passage, ice-induced scour, and research needs are discussed. However, as outlined in the paper, research on ice loads and passage at bridge sites and on hydroclimatic and ice conditions that led to bridge damage and failure remains needed. [ABSTRACT FROM AUTHOR]

River concentrations of suspended sediment and particulate contaminants, such as trace metals, increase sharply during ice breakup, with potentially detrimental ecological impacts that may be complicated by changing climatic conditions. To enhance the very limited knowledge on this issue, comprehensive data have been collected on the Saint John River (SJR). During breakup, the suspended sediment concentration (SSC) was found to rise gradually, crest, and decline, roughly in step with the runoff, but occasionally spiked to extremely high peaks. The latter ranged from 4.2 to 6.5 times the runoff-generated peak concentrations (RPCs), which ranged from 35 to 150 mg/L. Peak RPCs and individual-event sediment loads generally increased with flow discharge. The sediment spikes were invariably associated with waves resulting from releases of upstream ice jams and with the ensuing ice runs. Concentration–discharge graphs exhibited pronounced clockwise hysteresis, indicative of sediment supply constraints. This feature is more prominent in high-runoff events and typically associated with a lag of 1–3 days between peak concentration and peak discharge, which arrives later. Prediction of SSC via sediment-rating curves is hopeless, but such curves can be helpful in computing loads associated with individual events using a modified approach that terminates load computation 3 days after the arrival of peak discharge. The bulk of the sediment load is delivered on the rising limb of the hydrograph and is likely to be missed in routine sediment monitoring programs. Practical steps to capture this information are suggested. Increases in SJR spring flows during recent decades are projected to continue under a warming climate, resulting in considerable increases of SSCs and loads by the end of this century. [ABSTRACT FROM AUTHOR]

In semi-arid and arid regions, civil engineers may be required to plan measures, such as sand fences, to control sand movement affecting developed areas or transportation corridors. In this paper, considering the desertification process for the Minqin Oasis in Gansu Province, China, the design of sand fences and overall sand control strategies to lessen the rate of desertification are discussed. A sand transport model called MOSAND was developed to predict the sand transport rate for the Minqin Oasis. The model was based on a bed load transport (creep and saltation) equation and a logarithmic velocity profile for the wind. Using the measured wind data for the Minqin area, a monthly average sand transport rate was calculated that was used to determine an effective life span of a 3 m high sand fence. Sand fences in conjunction with straw checkerboard sand barriers are recommended to control sand drifts into the Minqin Oasis. [ABSTRACT FROM AUTHOR]

Abstract: During the 1994 and 1995 spring breakup events, ice jams were formed on the lower Matapedia River and remained in place long enough to permit collection of detailed field data on jam thickness as well as on water surface elevations. Together with bathymetric data that were obtained in the following summers, the spring measurements form one of the most complete ice-jam data sets that have been obtained to date. This allowed examination of how well current understanding of the hydromechanics of ice jams, incorporated in a numerical model, can describe the results of the measurements. The availability of jam thickness data was particularly advantageous because it removed the ambiguity associated with model calibrations that are solely based on water level measurements. With suitable choice of the model parameters, the model reproduced the measured water level profiles of the jam very closely, while providing reasonable simulations of jam thickness. The selected values of the model parameters were consistent with values established by previous applications on other rivers, and almost identical between the two Matapedia jams, despite contrasts in jam severity and river flow. Model sensitivity was explored using the more complete 1995 data set and found to be moderate. The detail of the available data also made it possible to scrutinize hydraulic resistance characteristics of flows underneath ice jams, and confirm earlier formulations specifically designed to address extreme-roughness conditions. [Copyright &y& Elsevier]

Recent work on climatic change indicates that the frequency and severity of flooding in many parts of the world could increase due to major changes in the hydroclimatic regime and a continuing rise in mean sea level. Changes in the magnitude and intensity of precipitation and the timing of runoff will increase riverine flooding, including the occurrence of midwinter ice-jam floods in northern rivers. Higher sea levels will increase the likelihood of coastal flooding and problems with urban infrastructure draining to tidal estuaries. Unless action is taken to lessen the vulnerability of human settlements, flood damages will increase. Adaptation strategies are needed that identify and direct development away from flood-prone areas, and incorporate infrastructure design criteria that take a changing climate into account. In this paper, a methodological approach to developing strategies for flood management is presented. After considering the occurrence and potential consequences of floods, and the importance and means of flood management, the impacts of climate change on flood mitigation are considered. Key elements of a generic adaptive strategy for floodplain management are then proposed, and, finally, the implementation of a flood management program is discussed. [ABSTRACT FROM AUTHOR]

Abstract: The water temperature decay under ice jams that form during the breakup of the river ice cover is evaluated using different data sets from several Canadian rivers. In all cases, the water temperature varies with downstream distance in negative exponential fashion, as indicated by a simplified, one-dimensional, formulation of heat conservation in a river. The corresponding heat transfer coefficients and derivative dimensionless quantities are very high relative to the values that would be expected by extrapolation of existing formulae for turbulent convection in rough pipes. It is suggested that these high heat transfer rates are due to two factors, both characteristic of breakup ice jams: the extreme roughness of the jam underside, and the flow through the voids of the accumulation of ice blocks that comprise the jam. [Copyright &y& Elsevier]

Surges are the most violent and spectacular events that occur during the ice breakup. Upon the release of an ice jam, water and ice held by the jam are suddenly free to move. The resulting surge generates increased water stages and higher flow velocities, such that the water wave and ice run pose a risk to downstream structures, people, and aquatic life. Climate-induced changes to river ice processes, such as enhanced mid-winter jamming or increased spring flows, could result in more frequent occurrence of major and damaging surges. To address a dearth of related quantitative data, a remote water-level reporting method has been developed and used to obtain field measurements on ice-jam generated surges. The results are consistent with the few available data but only partly conform to existing theories. [ABSTRACT FROM AUTHOR]

Upon the release of an ice jam, a wave or surge results that generates increased water stages and much higher flow velocities, posing various risks to local river ecology as well as to river structures and riverside communities. The temporal waveform can be easily measured, using water-level sensors, but the hydrodynamic characteristics of the surge, such as celerity, flow velocity, discharge, and shear stress, remain difficult to determine. An analytical method to deduce these parameters is developed herein, based on the equations of motion and plausible approximations for natural stream geometry. Preliminary comparisons with recent field measurements show promising results and demonstrate the degree to which a surge can magnify hydrodynamic forces. The methodology can be used in various applications, such as assessing the severity of a breakup event, estimating flow discharge during the passage of a wave, or evaluating scour potential in ecologically sensitive reaches and at river crossings. [ABSTRACT FROM AUTHOR]

Discusses climatic factors and impacts relative to river ice engineering and science. Background on climatic change; Description of responses to climatic change; Details on probable changes to ice breakup processes.

Delineation of flood hazard and risk on maps is useful as a means of public education and as a basis for measures aimed at lessening future flood damages. In many northern countries, rivers and streams are prone to ice-related flooding that often results in higher water levels and more extensive damages than open-water events. Procedures and standards for analysing ice-related flooding, however, are much less common than well-established standardized approaches for the open-water events. Nonetheless, the inherent flood hazard along many northern and mid-latitude rivers is not fully represented on flood-plain, flood-hazard, and flood-risk mapping if the possibility of ice-jam floods is ignored. Fortunately, the biophysical, past-flood, and flood-envelope approaches for flood hazard can be readily applied to ice-related floods, and hydrotechnical approaches based on an improved understanding of river-ice processes have been developed. In this paper, the nature and severity of ice-jam flooding, the present status of delineating ice-related flood events, and challenges to delineating ice-related floods are discussed. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including river ice engineering, public domain numerical models which can be used to model the consequences of ice jam formation or river ice regimes, and the effects of river ice.

In a river with seasonal ice covers, river ice effects must be considered in the design and operation of water control structures such as dams, barrages, and spillways. The regulation of flow and the water levels of rivers and reservoirs have several hydrological, socio-economic, and ecological effects. Regulation alters river-ice regimes by modifying the temporal and spatial characteristics of flow, water level, and thermal regimes in a watercourse. Removal of a water control structure and reservoir can eliminate some problems, but create new problems in areas where environmental or development conditions have changed. Therefore, thorough review of proposals to regulate (or remove regulation on) a river with seasonal ice covers is necessary. The effects of regulation on ice conditions and vice-versa are reviewed in this paper. Although considerable progress has been made during recent years, adequate understanding of the effects of river-ice interaction with structures and the effect of regulation on geomorphology, people, and aquatic habitat requires additional research. [ABSTRACT FROM AUTHOR]

The passage of river ice during the breakup event can have several effects on bridge structures. Design for ice passage at bridges has largely been empirical, such as the determination of superstructure clearance requirements based on historical stage data. As hydrologic and river ice processes in rivers are modified by climatic change, the use of empirical methods based on past observations and measurements could become less reliable. To advance beyond empiricism, it is necessary to develop rational design criteria based on a thorough understanding of the factors governing the interaction between bridges and ice. This concern applies especially during the breakup event when river flows, velocities, and hydrodynamic forces are usually higher and moving ice is thicker and stronger than during freeze-up. This paper provides guidance on the design of bridges to minimize ice impacts on the structure during the breakup period. [ABSTRACT FROM AUTHOR]

Bridges can impede the passage of river ice during the breakup event and promote formation of ice jams, with adverse socioeconomic and ecological impacts. Design for ice passage at bridges has largely been empirical and qualitative so that avoidance of ice-jam instigation is often uncertain. It is thus important to develop rational design criteria, based on a thorough understanding of the factors governing the interaction between bridges and ice. This concern is quantified by utilizing recent advances on breakup initiation and comparing driving and resisting forces when the sheet ice cover is about to be set in motion. Retention of ice sheets by in-stream piers can lead to jamming via accumulation of ice rubble that may be arriving from upriver. The resulting methodology is applied to two case studies and yields results that are in full accord with local experience. Though the present findings pertain to the obstruction created by in-stream piers, similar reasoning can be applied to constrictions that may be caused by protruding bridge abutments. [ABSTRACT FROM AUTHOR]

Presents a case study of midwinter ice jams on the upper Saint John River in Canada. Background on the environmental effects of ice breakup and jamming; Analysis of several ice breakup and jamming events in the area during the 1990s; Results and implications for planning flood control measures.