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Reliable estimation of design extreme rainfall at an ungauged site is regarded to be an important task in engineering hydrology. This study compares two approaches of extreme rainfall estimation at ungauged locations: region-of-influence (ROI) approach of regional estimation and interpolation-based at-site estimation in a lowlying country where the density of rainfall measurements is relatively low. Both approaches incorporate generalized extreme value (GEV) based index-flood estimation procedure in which the growth factor is used as the means of comparison. The geographical proximity based ROI scheme is assessed for its suitability in ungauged cases whereas popular interpolation techniques-inverse distance weighting (IDW) and kriging-are examined to find an appropriate model for the same purpose. The estimation of index is required in the index-flood method to get a complete frequency curve at ungauged locations. This study also compares several interpolation approaches in this regard. Annual maximum daily rainfall data at 34 stations located in Bangladesh have been used to assess the performance. The successful evaluation of homogeneity test and the unbounded characteristics of frequency model prove the appropriateness of the ROI scheme in ungauged conditions. The ordinary kriging (OK) is found to be superior to the IDW method in terms of cross-validation error measures. The estimates of index rainfall obtained by OK with or without anisotropy produce very similar results, although a slight improvement is achieved when an anisotropic semi-variogram in east direction is used. Regarding comparison between OK and ROI, both methods show a similar performance, indicating that both can be used for ungauged estimation. The overall results suggest that the spatial information about rainfall is an important factor in terms of formation of governing character of extreme rainfall in a low-lying region like Bangladesh.

Abstract. Flood frequency analysis is a necessary and important part of flood risk assessment and management studies. Regional flood frequency methods, in which flood data from groups of catchments are pooled together in order to enhance the precision of flood estimates at project locations, is an accepted part of such studies. This enhancement of precision is based on the assumption that catchments so pooled together are homogeneous in their flood producing properties. If homogeneity is assured then a homogeneous pooling group of sites lead to a reduction in the error of quantile estimates, relative to estimators based on single at-site data series alone. Homogeneous pooling groups are selected by using a previously nominated rule and this paper examines how effective one such rule is in selecting homogeneous groups. In this paper a study, based on annual maximum series obtained from 85 Irish gauging stations, examines how successful a common method of identifying pooling group membership is in selecting groups that actually are homogeneous. Each station has its own unique pooling group selected by use of a Euclidean distance measure in catchment descriptor space, commonly denoted d ij and with a minimum of 500 station years of data in the pooling group. It was found that d ij could be effectively defined in terms of catchment area, mean rainfall and baseflow index. The study then investigated how effective this selected method is in selecting groups of catchments that are actually homogenous as indicated by their L-Cv values. The sampling distribution of L-CV (t 2 ) in each pooling group and the 95% confidence limits about the pooled estimate of t 2 are obtained by simulation. The t 2 values of the selected group members are compared with these confidence limits both graphically and numerically. Of the 85 stations, only 1 station's pooling group members have all their t 2 values within the confidence Correspondence to: S. Das (samirandas@gmail.com) limits, while 7, 33 and 44 of them have 1, 2 or 3 or more, t 2 values outside the confidence limits. The outcomes are also compared with the heterogeneity measures H1 and H2. The H1 values show an upward trend with the ranges of t 2 values in the pooling group whereas the H2 values do not show any such dependency. A selection of 27 pooling groups, found to be heterogeneous, were further examined with the help of box-plots of catchment descriptor values and one particular case is considered in detail. Overall the results show that even with a carefully considered selection procedure, it is not certain that perfectly homogeneous pooling groups are identified.

Pooling of flood data is widely used to provide a framework to estimate design floods by the Index Flood method. Design flood estimation with this approach involves derivation of a growth curve which shows the relationship between X T and the return period T, where X T = Q T /Q I and Q I is the index flood at the site of interest. An implicit assumption with the Index Flood procedure of pooling analysis is that the X T -T relationship is the same at all sites in a homogeneous pooling group, although this assumption would generally be violated to some extent in practical cases, i.e. some degree of heterogeneity exists. In fact, in only some cases is the homogeneity criterion effectively satisfied for Irish conditions. In this paper, the performance of the index-flood pooling analysis is assessed in the Irish low CV (coefficient of variation) hydrology context considering that heterogeneity is taken into account. It is found that the performance of the pooling method is satisfactory provided there are at least 350 station years of data included. Also it is found that, in a highly heterogeneous group, it is more desirable to have many sites with short record lengths than a smaller number of sites with long record lengths. Increased heterogeneity decreases the advantage of pooling group-based estimation over at-site estimation. Only a heterogeneity measure (H1) less than 4.0 can render the pooled estimation preferable to that obtained for at-site estimation for the estimation of 100-year flood. In moderately to highly heterogeneous regions it is preferable to conduct at-site analysis for the estimation of 100-year flood if the record length at the site concerned exceeds 50.Key words regional flood frequency analysis; pooling group; low CV hydrology Performances de l'analyse de fréquence de crues regroupées dans un contexte de coefficient de variation faible Résumé Le regroupement de données sur les crues est largement utilisé pour fournir un cadre d'évaluation des crues de projet par la méthode de l'indice de crue. L'estimation par cette approche des crues de projet implique d'établir une courbe de la relation entre X T et la période de retour T, où X T = Q T /Q I et où Q I est l'indice de crue au site étudié. Une hypothèse implicite à la méthode de l'indice de crue appliquée à un regroupement de données est que la relation entre X T et T soit la même pour tous les sites regroupés, alors que ce n'est pratiquement pas toujours le cas, dès lors qu'il existe une certaine hétérogénéité. En fait, ce n'est que dans certains cas que le critère d'homogénéité est effectivement satisfait en Irlande. Dans cet article, on évalue les performances de l'analyse par la méthode de l'indice de crue dans le contexte hydrologique irlandais où le CV (coefficient de variation) est faible, en considérant que l'hétérogénéité est prise en compte. On constate que la performance de la méthode de regroupement est satisfaisante à condition que le regroupement comprenne au moins 350 ans de données. On a également constaté que, dans un g...

This work was carried out in collaboration between both authors. Author SD designed the study, performed the statistical analysis, wrote the protocol, and wrote the first draft of the manuscript. Author SPS assisted the study design, supervised the analyses, reviewed the first draft of the manuscript and helped with the revisions. Both authors read and approved the final manuscript.

Context:Since the home is the primary source of exposure of children to second-hand smoke (SHS), measures to restrict smoking at home should be introduced to protect children from its adverse health consequences.Aims:Objectives of the study were to assess the level of awareness of rural Indian women on the health impacts of SHS on children and to look into the strategies they used to reduce children's exposure to SHS at home.Materials and Methods:A community-based cross-sectional study was conducted among 438 rural women using a survey questionnaire. Information on socio-demographic characteristics, knowledge on specific health effects of SHS on children, and attitude toward having a smoke-free home were collected. The perceived reasons that made it difficult to have smoke-free homes were also explored.Results:A total of 75.8% of women agreed that SHS was a serious health risk for children. Knowledge on health impacts of SHS on children identified asthma as the most common problem. Smoking by husbands (89.7%) was the major source of exposure to SHS at home. While 67.6% of women reported having taken measures to limit SHS exposure in their homes, only 12.8% of them had tried to introduce a complete ban on smoking at home. On a five-point evaluation scale, 73.3% of the women indicated a failure of their initiatives to have smoke-free homes.Conclusions:Women's initiatives to introduce restrictions on smoking at home had very limited success and did not produce an appreciable change in smoking behavior at home. Lack of empowerment of women in rural India probably rendered the interventional measures ineffective.