Breach erosion of earthfill dams (BEED) model

A computer model has been developed for simulation of breach erosion of earthfill dams (BEED). The model incorporates the processes of surface erosion and slope sloughing to simulate breach enlargement. Depletion of reservoir water is approximated by a volume continuity equation while broad-crested weir hydraulics is utilized to describe flow over and through the breach. Due to the implicit form of these equations, an iterative solution is proposed with convergence achieved within only a few iterations. The BEED model is written in both FORTRAN 77 and BASIC computer languages. Testing of the model using historical data of the failures of Teton and Huaccoto dams showed that timing, shape, and magnitude of the predicted outflow hydrograph were adequately simulated by this model. The same is true for the dimensions of the terminal breach. A sensitivity analysis indicated that internal friction angle and the relation for surface erosion were the major factors affecting the model results.     

Flooding of Sinking Creek,Garretts Spring karst drainage basin,Jessamine and Woodford counties,Kentucky, USA

Tashamingo Subdivision in Sinking Creek karst valley, a tributary of the Garretts Spring drainage basin in Jessamine and Woodford counties, Kentucky, was flooded in February 1989. To determine the cause of flooding, the groundwater basin boundary was mapped, discharge data were measured to determine intake capacity of swallets, and hydrologic modeling of the basin was conducted. Swallet capacity was determined to be limited by the hydraulic parameters of the conduit, rather than by obstruction by trash. Flooding from a precipitation event is more likely, and will be higher, when antecedent soil moisture conditions in the watershed are near saturation. Hydrologic modeling shows that suburban development of 20 percent of the southeast basin will cause a small increase in flood stage at Tashamingo Subdivision.     

1995年我国天气气候特点

１９９５年，我国大部地区降水正常或偏多，但季节分配不均。春季，北方干旱范围较大，陕、甘等省冬春夏连旱，旱情严重。汛期，江南及东北南部暴雨频繁，赣、湘、辽、吉等省发展严重洪涝。全国大部地区热量比较充足，但光照条件欠佳，部分地区作物遭受低温寡照或霜冻危害。登陆台风和热带风暴偏多，两广局地损失严重。部分地区遭受风雹或沙尘暴袭击。     

永登5.8级地震的社会经济影响

本文详细介绍了永登５．８级地震引起的各种不良社会现象和政府采取的相应措施，同时，就这次地震造成的经济损失和重建家园的经济预算进行了详细的介绍和估算。可供从事地震社会学的同行在防震减灾工作中参考。     

Non-equilibrium alcohol flooding model for immiscible phase remediation: 1. Equation development

The equations for a compositional model for simulation of a two-phase, three-component system with inter-phase mass transfer are developed. Emphasis is placed on development of inter-phase mass transfer equations for incorporation of rate-limited inter-phase mass transfer. Due to the nature of the three-component systems considered, a single-film model may be inadequate and a two-film model must be utilized. A two-film model accounts for the simultaneous transfer of components in both directions across phase interfaces. The effect of interaction between components on diffusion is considered using a general form of Fick's Law. A Hand Plot representation of ternary phase behavior is chosen since it allows for straightforward calculation of miscibility of bulk phases under conditions of local non-equilibrium. The developed set of equations form the basis for a numerical model to simulate the enhanced removal of non-aqueous phase liquids (NAPLs) from porous media using single-component alcohol floods.     

Simulation of the spatio‐temporal extent of groundwater flooding using statistical methods of hydrograph classification and lumped parameter models

This article presents the development of a relatively low cost and rapidly applicable methodology to simulate the spatio‐temporal occurrence of groundwater flooding in chalk catchments. In winter 2000/2001 extreme rainfall resulted in anomalously high groundwater levels and groundwater flooding in many chalk catchments of northern Europe and the southern United Kingdom. Groundwater flooding was extensive and prolonged, occurring in areas where it had not been recently observed and, in places, lasting for 6 months. In many of these catchments, the prediction of groundwater flooding is hindered by the lack of an appropriate tool, such as a distributed groundwater model, or the inability of models to simulate extremes adequately. A set of groundwater hydrographs is simulated using a simple lumped parameter groundwater model. The number of models required is minimized through the classification and grouping of groundwater level time‐series using principal component analysis and cluster analysis. One representative hydrograph is modelled then transposed to other observed hydrographs in the same group by the process of quantile mapping. Time‐variant groundwater level surfaces, generated using the discrete set of modelled hydrographs and river elevation data, are overlain on a digital terrain model to predict the spatial extent of groundwater flooding. The methodology is applied to the Pang and Lambourn catchments in southern England for which monthly groundwater level time‐series exist for 52 observation boreholes covering the period 1975–2004. The results are validated against observed groundwater flood extent data obtained from aerial surveys and field mapping. The method is shown to simulate the spatial and temporal occurrence of flooding during the 2000/2001 flood event accurately. British Geological Survey © NERC 2011. Hydrological Processes © 2011 John Wiley & Sons, Ltd.     

Climate variability,snow, and physiographic controls on storm hydrographs in small forested basins,western Cascades,Oregon

Large floods are often attributed to the melting of snow during a rain event. This study tested how climate variability, snowpack presence, and basin physiography were related to storm hydrograph shape in three small (<1 km²) basins with old‐growth forest in western Oregon. Relationships between hydrograph characteristics and precipitation were tested for approximately 800 storms over a nearly 30‐year period. Analyses controlled for (1) snowpack presence/absence, (2) antecedent soil moisture, and (3) hillslope length and gradient. For small storms (<150 mm precipitation), controlling for precipitation, the presence of a snowpack on near‐saturated soil increased the threshold of precipitation before hydrograph rise, extended the start lag, centroid lag, and duration of storm hydrographs, and increased the peak discharge. The presence of a snowpack on near‐saturated soil sped up and steepened storm hydrographs in a basin with short steep slopes, but delayed storm hydrographs in basins with longer or more gentle slopes. Hydrographs of the largest events, which were extreme regional rain and rain‐on‐snow floods, were not sensitive to landform characteristics or snowpack presence/absence. Although the presence of a snowpack did not increase peak discharge in small, forested basins during large storms, it had contrasting effects on storm timing in small basins, potentially synchronizing small basin contributions to the larger basin hydrograph during large rain‐on‐snow events. By altering the relative timing of hydrographs, snowpack melting could produce extreme floods from precipitation events whose size is not extreme. Further work is needed to examine effects of canopy openings, snowpack, and climate warming on extreme rain‐on‐snow floods at the large basin scale. Copyright © 2008 John Wiley & Sons, Ltd.     

Assessing possible changes in flood frequency due to climate change in mid‐sized watersheds in New York State,USA

The frequency of flooding is often presumed to increase with climate change because of projected increases in rainfall intensities. In this paper, using 50‐plus years of historical discharge and meteorological data from three watersheds in different physiographic regions of New York State, USA, we find that annual maximum stream discharges are associated with 20% or less of the annual maximum rainfall events. Instead of rainfall events, approximately 20% of annual maximum stream discharges are associated with annual maximum snowmelt events while 60% of annual maximum discharges are associated with moderate rainfall amounts and very wet soil conditions. To explore the potential for changes in future flood risk, we employed a compound frequency distribution that assumes annual maximum discharges can be modelled by combining the cumulative distribution functions of discharges resulting from annual maximum rainfall, annual maximum snowmelt, and occurrences of moderate rain on wet soils. Basing on a compound frequency distribution comprised of univariate general extreme value (GEV) and gamma distributions, we found that a hypothetical 20% increase in the magnitude of rainfall‐related stream discharge results in little change in 96th percentile annual maximum discharge. For the 99th percentile discharge, two waterbodies in our study had a 10% or less increase in annual maximum discharge when annual maximum rainfall‐related discharges increased 20% while the third waterbody had a 16% increase in annual maximum discharges. Additionally, in some cases, annual maximum discharges could be offset by a reduction in the discharge resulting from annual maximum snowmelt events. While only intended as a heuristic tool to explore the interaction among different flood‐causing mechanisms, use of a compound flood frequency distribution suggests a case can be made that not all waterbodies in humid, cold regions will see extensive changes in flooding due to increased rainfall intensities. Copyright © 2011 John Wiley & Sons, Ltd.     

Deterministic and ensemble storm surge prediction for Atlantic Canada with lead times of hours to ten days

Regional deterministic and ensemble surge prediction systems (RDSPS and RESPS respectively) are used to forecast sea levels off the east of Canada and northeast US. The surge models for the RDSPS and RESPS have grid spacings of 1/30° and 1/12° respectively. The models are driven by surface air pressure and 10 m winds generated by operational global deterministic and ensemble prediction systems that are run operationally by the Canadian Meteorological Centre. Surge forecasts are evaluated for the period 1 March, 2013 to 31 March 2014. Based on traditional statistics (e.g., standard deviation of the difference between observations and predictions) both systems are shown to have skill in forecasting surges six days into the future. It is shown however that skill exists beyond six days if allowance is made for errors in the timing of large surges. The usefulness of the RESPS is demonstrated for two positive surges (important for coastal flooding and erosion) and a negative surge (important for safe navigation in shallow water). It is shown that the RESPS can identify events not forecast by the RDSPS, and can also add useful additional information on the timing of the surge, an important consideration in tidally dominated waters. Several new types of display are used to illustrate the sort of information that can be generated by the RESPS to support the issuers of warnings of unusually high and low total water levels.     

旋挖钻机聚合物泥浆施工技术浅探

通过对聚合物泥浆护壁机理的分析,简要叙述了聚合物泥浆的性能特点,为在旋挖钻孔工艺中应用聚合物泥浆,总结了聚合物泥浆的制备、回收、净化、排放方法,优化了施工时泥浆循环系统的布置方案。结合工程实践,指出了旋挖钻进时应注意的问题和对一些易出现问题的处理方法,对旋挖钻机应用聚合物泥浆施工时具有一定的指导意义。