Credibility of design rainfall estimates for drainage infrastructures: extent of disregard in Nigeria and proposed framework for practice

Daily extreme precipitation values are among environmental events with the most disastrous consequences for human society. Information on the magnitudes and frequencies of extreme precipitations is essential for sustainable water resources management, planning for weather-related emergencies, and design of hydraulic structures. In the present study, regional frequency analysis of maximum daily rainfalls was investigated for Golestan province located in the northeastern Iran. This study aimed to find appropriate regional frequency distributions for maximum daily rainfalls and predict the return values of extreme rainfall events (design rainfall depths) for the future. L-moment regionalization procedures coupled with an index rainfall methodwere applied to maximum rainfall records of 47 stations across the study area. Due to complex geographicand hydro-climatological characteristics of the region, an important research issue focused on breaking downthe large area into homogeneous and coherent sub-regions. The study area was divided into five homogeneousregions, based on the cluster analysis of site characteristics and tests for the regional homogeneity.The goodness-of-fit results indicated that the best fitting distribution is different for individual homogeneousregions. The difference may be a result of the distinctive climatic and geographic conditions. The estimatedregional quantiles and their accuracy measures produced by Monte Carlo simulations demonstrate that theestimation uncertainty as measured by the RMSE values and 90% error bounds is relatively low when returnperiods are less than 100 years. But, for higher return periods, rainfall estimates should be treated withcaution. More station years, either from longer records or more stations in the regions, would be required forrainfall estimates above T=100 years. It was found from the analyses that, the index rainfall (at-site averagemaximum rainfall) can be estimated reasonably well as a function of mean annual precipitation in Golestanprovince. Index rainfalls combined with the regional growth curves, can be used to estimate design rainfallsat ungauged sites. Overall, it was found that cluster analysis together with the L-moments based regional frequencyanalysis technique could be applied successfully in deriving design rainfall estimates for northeasternIran. The approach utilized in this study and the findings are of great scientific and practical merit, particularlyfor the purpose of planning for weather-related emergencies and design of hydraulic engineering structures

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A shortcut to seasonal design rainfall estimates in the UK

Water and Environment Journal ◽

10.1111/j.1747-6593.2006.00028.x ◽

2006 ◽

Vol 20 (4) ◽

pp. 282-286 ◽

Cited By ~ 1

Author(s):

T. R. Kjeldsen ◽

C. Prudhomme ◽

C. Svensson ◽

E. J. Stewart

Keyword(s):

Design Rainfall ◽

The Uk ◽

Rainfall Estimates

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The Influence of Geographical Factors on Extreme Rainfalls in Lampung Province

Journal of Engineering and Scientific Research ◽

10.23960/jesr.v1i1.7 ◽

2019 ◽

Vol 1 (1) ◽

pp. 33

Author(s):

M Welly

Keyword(s):

Geographical Location ◽

Daily Rainfall ◽

Extreme Rainfall ◽

Design Flood ◽

Extreme Rainfall Events ◽

Rainfall Events ◽

Ungauged Basin ◽

Flood Discharge ◽

Design Rainfall ◽

Geographical Factors

Many people in Indonesia calculate design rainfall before calculating the design flooddischarge. The design rainfall with a certain return period will eventually be convertedinto a design flood discharge by combining it with the characteristics of the watershed.However, the lack of a network of rainfall recording stations makes many areas that arenot hydrologically measured (ungauged basin), so it is quite difficult to know thecharacteristics of rain in the area concerned. This study aims to analyze thecharacteristics of design rainfall in Lampung Province. The focus of the analysis is toinvestigate whether geographical factors influence the design rainfall that occurs in theparticular area. The data used in this study is daily rainfall data from 15 rainfallrecording stations spread in Lampung Province. The method of frequency analysis usedin this study is the Gumbel method. The research shows that the geographical location ofan area does not have significant effect on extreme rainfall events. The effect of risingearth temperatures due to natural exploitation by humans tends to be stronger as a causeof extreme events such as extreme rainfall.Keywords: Influence, geographical, factors, extreme, rainfall.

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The inspection of actual runoff control facilities five years after construction

Water Science & Technology ◽

10.2166/wst.1997.0695 ◽

1997 ◽

Vol 36 (8-9) ◽

pp. 373-377

Author(s):

Yuzo Akagawa ◽

Yasutoshi Matsumoto ◽

Mitsuyoshi Zaizen

Keyword(s):

Return Period ◽

Social Background ◽

Groundwater Table ◽

Control Functions ◽

Design Rainfall ◽

The Social ◽

Athletic Field ◽

Runoff Control

This report describes runoff control facilities (five years after construction) which are basically an athletic field consisting of tennis courts, constructed in an area of about four hectares in Tokyo. The report is divided into three parts. The first part deals with the social background of the fact that the athletic field has come to have runoff control functions. The second part concerns the summary of these facilities, and then the last part relates to the effects of runoff control. Concerning the effects of the facilities, the return period of design rainfall for runoff control facilities is ten years, but stormwater has been stored on the tennis courts twice in five years after construction. Though these two cases of rainfall were very extraordinary, as the outcome of the inspection of the runoff control facilities we were able to confirm the effects of runoff control by means of simulating under the condition of those two cases of rainfall. In addition, we were able to confirm the effect of groundwater cultivation by means of researching the transition of the groundwater table.

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A susceptibility-based rainfall threshold approach for landslide occurrence

Natural Hazards and Earth System Science ◽

10.5194/nhess-19-775-2019 ◽

2019 ◽

Vol 19 (4) ◽

pp. 775-789 ◽

Cited By ~ 12

Author(s):

Elise Monsieurs ◽

Olivier Dewitte ◽

Alain Demoulin

Keyword(s):

Landslide Susceptibility ◽

Rainfall Threshold ◽

Exceedance Probability ◽

Equal Weight ◽

Antecedent Rainfall ◽

Rainfall Thresholds ◽

Landslide Occurrence ◽

Continental Scale ◽

Satellite Rainfall ◽

Rainfall Estimates

Abstract. Rainfall threshold determination is a pressing issue in the landslide scientific community. While major improvements have been made towards more reproducible techniques for the identification of triggering conditions for landsliding, the now well-established rainfall intensity or event-duration thresholds for landsliding suffer from several limitations. Here, we propose a new approach of the frequentist method for threshold definition based on satellite-derived antecedent rainfall estimates directly coupled with landslide susceptibility data. Adopting a bootstrap statistical technique for the identification of threshold uncertainties at different exceedance probability levels, it results in thresholds expressed as AR = (α±Δα)⋅S(β±Δβ), where AR is antecedent rainfall (mm), S is landslide susceptibility, α and β are scaling parameters, and Δα and Δβ are their uncertainties. The main improvements of this approach consist in (1) using spatially continuous satellite rainfall data, (2) giving equal weight to rainfall characteristics and ground susceptibility factors in the definition of spatially varying rainfall thresholds, (3) proposing an exponential antecedent rainfall function that involves past daily rainfall in the exponent to account for the different lasting effect of large versus small rainfall, (4) quantitatively exploiting the lower parts of the cloud of data points, most meaningful for threshold estimation, and (5) merging the uncertainty on landslide date with the fit uncertainty in a single error estimation. We apply our approach in the western branch of the East African Rift based on landslides that occurred between 2001 and 2018, satellite rainfall estimates from the Tropical Rainfall Measurement Mission Multi-satellite Precipitation Analysis (TMPA 3B42 RT), and the continental-scale map of landslide susceptibility of Broeckx et al. (2018) and provide the first regional rainfall thresholds for landsliding in tropical Africa.

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Reanalysis Product-Based Nonstationary Frequency Analysis for Estimating Extreme Design Rainfall

Atmosphere ◽

10.3390/atmos12020191 ◽

2021 ◽

Vol 12 (2) ◽

pp. 191

Author(s):

Dong-IK Kim ◽

Dawei Han ◽

Taesam Lee

Keyword(s):

South Korea ◽

20Th Century ◽

Frequency Analysis ◽

Systematic Errors ◽

Quantile Mapping ◽

Reanalysis Product ◽

Rainfall Analysis ◽

Future Evolution ◽

Design Rainfall ◽

Nonstationary Frequency

Nonstationarity is one major issue in hydrological models, especially in design rainfall analysis. Design rainfalls are typically estimated by annual maximum rainfalls (AMRs) of observations below 50 years in many parts of the world, including South Korea. However, due to the lack of data, the time-dependent nature may not be sufficiently identified by this classic approach. Here, this study aims to explore design rainfall with nonstationary condition using century-long reanalysis products that help one to go back to the early 20th century. Despite its useful representation of the past climate, the reanalysis products via observational data assimilation schemes and models have never been tested in representing the nonstationary behavior in extreme rainfall events. We used daily precipitations of two century-long reanalysis datasets as the ERA-20c by the European Centre for Medium-Range Weather Forecasts (ECMWF) and the 20th century reanalysis (20CR) by the National Oceanic and Atmospheric Administration (NOAA). The AMRs from 1900 to 2010 were derived from the grids over South Korea. The systematic errors were downgraded through quantile delta mapping (QDM), as well as conventional stationary quantile mapping (SQM). The evaluation result of the bias-corrected AMRs indicated the significant reduction of the errors. Furthermore, the AMRs present obvious increasing trends from 1900 to 2010. With the bias-corrected values, we carried out nonstationary frequency analysis based on the time-varying location parameters of generalized extreme value (GEV) distribution. Design rainfalls with certain return periods were estimated based on the expected number of exceedance (ENE) interpretation. Although there is a significant range of uncertainty, the design quantiles by the median parameters showed the significant relative difference, from −30.8% to 42.8% for QDM, compared with the quantiles by the multi-decadal observations. Even though the AMRs from the reanalysis products are challenged by various errors such as quantile mapping (QM) and systematic errors, the results from the current study imply that the proposed scheme with employing the reanalysis product might be beneficial to predict the future evolution of extreme precipitation and to estimate the design rainfall accordingly.

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Using satellite-based rainfall estimates for streamflow modelling: Bagmati Basin

Journal of Flood Risk Management ◽

10.1111/j.1753-318x.2008.00011.x ◽

2008 ◽

Vol 1 (2) ◽

pp. 89-99 ◽

Cited By ~ 52

Author(s):

M.S. Shrestha ◽

G.A. Artan ◽

S.R. Bajracharya ◽

R.R. Sharma

Keyword(s):

Rainfall Estimates

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Evaluating the accuracy of C- and X-band weather radars and their application for stream flow simulation

Journal of Hydroinformatics ◽

10.2166/hydro.2012.120 ◽

2012 ◽

Vol 15 (4) ◽

pp. 1121-1136 ◽

Cited By ~ 7

Author(s):

N. K. Shrestha ◽

T. Goormans ◽

P. Willems

Keyword(s):

Conceptual Model ◽

Stream Flow ◽

Flow Simulation ◽

Winter Storms ◽

Weather Radars ◽

X Band ◽

Rainfall Estimates

This paper investigates the accuracy of rainfall estimates from C- and X-band weather radars and their application for stream flow simulation. Different adjustment procedures are applied to raw radar estimates using gauge readings from a network of 12 raingauges. The stream flow is simulated for the 48.17 km2 Molenbeek/Parkbeek catchment located in the Flemish region of Belgium based on a lumped conceptual model. Results showed that raw radar estimates can be greatly improved using adjustment procedures. The gauge-radar residuals however, remain large even after adjustments. The adjusted X-band radar estimates are observed to be better estimates than corresponding C-band estimates. Their application for stream flow simulation showed that raingauges and radars can simulate spatially more uniform winter storms with almost the same accuracy, whereas differences are more evident on summer events.

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