Flood events

Flood Event Frequency Estimates were developed from flooding events in nuclear power plants with adjustments for plant-specific features and data. The data were from the IPE Surry flood analysis, industry sources, and licensing event reports (LERs). Some plant specific models were developed for the circulating water (CW) and service water (SW) lines... 

There are some descriptions of water-borne outbreaks, or even small epidemics of acute gastroenteritis (diarrhoea), cholera and hepatitis E associated with catastrophic floods that occurred in developing countries, such as Sudan [34, 35], Nicaragua [36], Mozambique [37] and West Bengal [37]. On the contrary, no changes in the base-line outbreak incidence have been reported in developed countries after major floods [37, 38]. When infrastructures and water management are adequate, outbreaks of faecal-oral water-borne infectious diseases do not follow flood events, even in the case where water flooding has compromised the security of water facilities [37]. 

Ludwig, J.P., Auman, H.J., and Kurita, H. et al. (1993). Caspian tern reproduction in the Saginaw Bay ecosystem following a 100 year flood event. Journal of Great Lakes Research 19, 96-108... 

Sediments Quality and quantity of sediments are an issue of concern, both in relation to the stored sediments in dams, and also concerning the possible remobilisation of sediment bound, historic contaminants as consequence of floods events. 

The western portion of the Thomson project area is classified as desert, with rainfall <250 mm/yr. The eastern portion is classified as grassland, with rainfall 250-500 mm/yr (Caritat Lech 2007). Summers are hot and dry, winters cool. Highly variable rainfall results in ephemeral streams, particularly in the west, and many of the creeks and rivers flow only during flood events, which can be significant events. The low-gradient, sinuous and anastomosing streams, creeks and rivers broaden to include flood plains often several kilometres wide. It is during these events that fine silts and clays from the upstream catchment are deposited on the floodplains. 

Fig. 17 Weighted frequency of the various process types [64]. Only flood events with a recurrence interval of more than 10 years are considered. These events are weighted as follows A process type which results in an event with a recurrence more than 30 years is accorded the weighting 3. A recurrence of more than 20 but less than 30 years corresponds to a weighting of 2, and a recurrence of more than 10 but less 20 years corresponds to a weighting of 1. The weightings are then aggregated for each process type per catchment...

Frei C, Davies HC, Gurtz J, Schar C (2000) Climate dynamics and extreme precipitation and flood events in Central Europe. Integr Assess 1 281-299... 

Table 2 Rhone (Porte du Scex) Comparison of retention impact of reservoirs in the catchment area during extreme flooding events in 1987, 1993, and 2000 [29]...

Ollivier, P., Radakovitch, O. and Hamelin, B. (2006) Unusual variations of dissolved As, Sb, and Ni in the Rh6ne River during flood events. Journal of Geochemical Exploration, 88, 394-98. 

Avoid sampling during rainy periods and flood events. The water sample must be taken before the stream sediment sample, for obvious reasons (during the collection of the stream sediment, fine-grained material is agitated and transported in suspension). The stream sediment sample is composited from 5-10 subsamples in the field. The water sample should be taken from the first, lowermost stream sediment sampling point. 

In areas of low relief, active stream sediment in the centre of channels may be enriched in quartz and depleted in clays and other fine particles. In these instances material deposited along stream margins during flood events may be finer grained and more suitable for geochemical sampling. 

Sampling during rainy periods and flood events was avoided. The water sample was always taken before the stream sediment sample, because during the collection... 

The water table is dynamic in most systems. It changes in response to rain events, flood events, snowmelt, recharge, and pumping. To decipher the interplay of these ongoing processes, periodic water table measurements are essential. Historical data are in many cases available from local water authorities, which conduct routine water table measurements. Measurement of the depth of the water table at the time of each sample collection is essential in order to couple the chemical and isotopic results with the hydrological data. 

Repeated water table measurements in a well may be presented on a hydrograph, as a function of time. In the example given in Fig. 4.7, the low water table may be interpreted as reflecting lack of recharge in the winter, and the rise may reflect snowmelt recharge followed by summer rains. Countless combinations of hydrograph shapes and modes of interpretation are possible. Knowledge of local precipitation and climate is needed for proper interpretation. Rapid response to rain or flood events may indicate... 

In September a sudden rise in the river was caused by a flood event, followed by an immediate rise of the water table in the well. 

Fig. 4.10 Water table fluctuations measured at wells near the Mohawk River (from Winslow et al., 1965). The wells followed a flood event with a time lag of several hours correlated with the distance from the river (insert table). The distance divided by the time lag provided the propagation velocity of the hydraulic pulse.

Repetition of field measurements and laboratory analyses is an essential part of hydrochemical studies. Sources of recharge vary over the year—summer rains, winter rains, and snowmelt. These are distinguishable by their isotopic (and occasionally also chemical) composition (Chapter 9), and their seasonal inputs can be established provided the relevant water systems are monitored over at least 1 year. Water table and discharge responses to precipitation or flood events provide information on hydraulic interconnec-... 

As shown in Figure 6.37(M6), the impedance spectra eventually return to the shape observed at the beginning of the measurement. The charge transfer arcs are slightly smaller and the spectrum of cell 2 has shifted towards the lower real parts, which is a result of better membrane hydration after the flooding event. 

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