All predictions and models must be grounded in appropriate and reliable field data, and the USGS should give data collection the highest priority in hydrologic hazards programs. The availability of gauged flows for large events with extreme discharges remains a challenge in South Africa. KwaZulu-Natal Premier Willies Mchunu has declared the province a disaster area after the devastating floods in Durban and surrounding area on 10 October 2017. After the initial selection of gauges, additional gauges with 15-20 years of record were investigated for inclusion in the analysis in areas which did not have any gauges included in the initial selection. Many international studies have shown that design floods estimated using a regionalised method result in more reliable estimates of design floods than values computed from a single site or from other methods. [ Links ], ALEXANDER WJR (2001) Flood Risk Reduction Measures. Pooled values for the coefficient of skewness (g) and coefficient of variation (CV) were weighted according to the record length and the inverse of a similarity distance (Disti,j), computed using Eq. 8. 241 pp. This breaking down into smaller fragments is necessary for improved understanding. (2000), Görgens (2007) and Haile (2011). The LC is always made to contain the address of the next memory word in the target program. Ideally, regionalisation in a RFFA should be performed using site characteristics as this enables independent testing of the regions for homogeneity using the at-site data, and the independent allocation of a site to a region based on the site characteristics. The statistical analysis I have done to calculate this are explained in my more detailed blog version of this article. The long-term synthetic flood records were generated by 68. The results from this study are applicable only to KZN and the performance of the various RFFA methods at a national scale needs to be investigated. 10, the JPV method using the regionalised GEV distribution and veld-zone regionalisation performed the best of the RFFA methods considered in this study. Data Analysis is the process of systematically applying statistical and/or logical techniques to describe and illustrate, condense and recap, and evaluate data. MSc Thesis, University of Oslo, Norway. [ Links ], SMITHERS JC and SCHULZE RE (2000a) Development and evaluation of techniques for estimating short duration design rainfall in South Africa. Discontinuities at regional boundaries need to be investigated and the alternative approach of transferring hydrological information from gauged to ungauged sites within a region should be evaluated. Together with the drought in the Western Cape, the wildfires on the Garden Route and the intense tropical cyclones Idai and Kenneth that have hit Mozambique, Zimbabwe and Malawi, they are part of a bigger picture of climate … Technical Report TR137. Keywords: regional flood frequency analysis, KwaZulu-Natal. The criteria used were length of record, with gauges included for record lengths > 20 years, start and end date of flow record, the percentage of values in the AMS where the recorded stage exceeded the limits of the rating curve for the flow-gauging station, the number of values in the AMS which were flagged as having missing data during the year, and the period of the year when the missing data occurred. mean annual flood) at ungauged sites in a region. DISCUSSION, CONCLUSIONS AND RECOMMENDATIONS. As shown in Fig. The Pearson Type 3 (P3) distribution fitted by probability weighted moments (PWM) was found to be the best distribution in all regions in South Africa, with the exception of SAF13 where the Log-Pearson Type 3 (LP3) distribution fitted by the Method of Moments (MM) was used. University of Pretoria, Pretoria. However, limitations of event-based methods include the assumption that the exceedance probability of the flood event is the same as the exceedance probability of the rainfall event, i.e., the 100-year return period flood event is assumed to result from a 100-year return period rainfall event, and the antecedent soil moisture condition in the catchment prior to extreme rainfall events is not taken into account. Equation 1 was used to estimate the MAF at ungauged sites (Mkhandi et al., 2000). The catchment descriptors (Desi) included catchment area, equal area catchment slope, MAR90, and an index of the veld type zone or K-region. 24 April 2019 - 12:24 By Orrin Singh. 28 April 2019. As shown in Fig. For the selected gauges used in this study, a single unique maximum value in the AMS was found at 87.8% of the gauges, and 12.2% of the sites had up to 15% of the years with the same maximum value. WRC Report No. 3. The government of KwaZulu-Natal (KZN) province in South Africa reports that thunderstorms have caused widespread damage in the province, and one person has died in flash floods. In some regions where the negative constant in the linear relationship resulted in a negative MEF, exponential relationships were developed in this study to estimate the MEF from catchment area using information from Haile (2011). KZN flood damage estimated at R1.1bn. for KZN the JPV method, with a regionalised GEV distribution with the veld zone regionalisation, generally gave the best performance when compared to design floods estimated from the annual maximum series extracted from the observed data. While the Haile method resulted in the smallest MAREM,D value, the average slope of the estimated vs. observed floods is considerably less than 1, indicating that the Haile method generally underestimates the floods computed from the observed data. ALEXANDER WJR (1990) Flood Hydrology for Southern Africa. A number of RFFA studies have been developed which include all of South Africa (Haile, Mkhandi and JPV methods), and regions of South Africa (Van Bladeren). 298/1/94. Region 1 covers the coastal and midlands area and Region 2 the west north-western parts of the study area. My findings are that this kind of drought occurs once in … [ Links ], HOSKING JRM and WALLIS JR (1997) Regional Frequency Analysis: An Approach Based on L-Moments. (2000) and Haile (2011) utilised the statistics of the at-site data with various homogeneity tests to identify homogenous flood regions in their study areas. Of the RFFA methods assessed in KZN, the Haile method gave the best performance in terms of the MARE, but consistently underestimated the design floods computed from the observed data when using either the GEV or LP3 distribution. Regionalisation was initially based on the Regional Maximum Flood (RMF) regions identified by Kovács (1988) and was further refined within the RMF regions based on the skewness of the data. Performance of regional flood frequency analysis methods in KwaZulu-Natal, South Africa, JC SmithersI, II, *; J StreatfieldII; RP GrayII; EGM OakesII, IBioresources Engineering, School of Engineering, University of KwaZulu-Natal, Private Bag X01, Scottsville, 3209, South Africa IIJeffares & Green (Pty) Ltd, 6 Pin Oak Avenue, Hilton, Pietermaritzburg, 3201, South Africa. A number of regional flood frequency analysis (RFFA) methods have been developed, which cover all or parts of South Africa. The results from an analysis of the performance of the RFFA methods are shown in Table 1, which includes both the MAREM,D values for each method and the average slope between the 2 to 100 year return period floods computed at each site using the selected method (Estimated) and estimated from the observed data at the site (Observed). Nine homogenous regions were identified, with 5 of these regions in South Africa, as shown in Fig. [ Links ], VAN DER SPUY D and RADEMEYER PF (2010) Flood Frequency Estimation Methods as Applied in the Department of Water Affairs. RFFA usually assumes that relatively homogenous flood regions can be identified where the frequency distributions of floods at different sites are similar after site-specific scaling. Despite the quality screening of the stations included in the study, the design floods estimated at a few stations seem to not be consistent with other stations in the region. 23 April, 2019 by FloodList News in Africa, News. In this regard most concern was expressed about operations of vessels that had been chartered from countries that did not insist on provision of data … Concept of “Memory Allocation” To implement memory allocation a data structure called location counter (LC) is used. 45 (3) 449-464. Spatial analysis is used to process this data into useful and meaningful information which can be used in making effective decisions during the planning process. [ Links ], MIDGLEY DC, PITMAN WV and MIDDLETON BJ (1994) Surface water resources of South Africa 1990. Stream flow-gauges located in KZN were selected for inclusion in the analysis based on the attributes of the gauges. Despite the advantages of a regional approach to design flood estimation, RFFA methods are not widely used in South Africa. 4. KZN hard hit by floods. The poor performance of the JPV method with the regionalised LP3 distribution needs to be investigated. The process of narrative data synthesis must therefore itself be rigorous and transparent, ideally with methods specified in advance (ie. Of the RFFA methods assessed in KZN, the Haile method gave the best performance in terms of the MARE, but consistently underestimated the design floods computed from the observed data when using either the GEV or LP3 distribution. Linear regression relationships were developed by Görgens (2007) to estimate the index flood, as shown in Eq. Support your findings with graphs, photos, etc. South Africa – Deadly Floods and Landslides Hit KZN and Eastern Cape. Cyril Ramaphosa promises funding to families hit by KZN floods. After screening of the data, only 122 stations were included in further analyses (Fig. Research Report RC 15658. The floods that claimed 80 lives, damaged homes and displaced over 1,500 people in the province did not spare the IEC. South Africa – Deadly Flash Floods in KwaZulu-Natal. In addition, design floods generally need to be estimated at sites where observed flood data are not available and thus rainfall-based methods or regionalised methods need to be used to estimate design floods at ungauged sites. [ Links ], CORDERY I and PILGRIM DH (2000) The state of the art of flood prediction. Daily precipitation and temperature data of the 11 quaternary catchments were obtained from QCD_DAT.EXE, a self-extracting compressed data file containing 50 years (1950–1999) of daily hydroclimatic data pertaining to each of the 1946 quaternary catchments of South Africa . Cambridge University Press, Cambridge, UK. (1984), for the analysis of AMS of rain and floods in KZN. 2 (Görgens, 2007). Floods. Cordery and Pilgrim, 2000; Hosking and Wallis, 1997; Smithers and Schulze, 2000a; Smithers and Schulze, 2000b). The frequency with which recorded flow stages exceed the maximum rated level needs to be quantified and the impact of not including these extreme events in the estimation of design floods in South Africa must be quantified. Handbook of Hydrology. Mkhandi et al. According to the provincial government, houses and bridges have been damaged in flood hit areas and residents living on river banks have had to be moved. The reliability of design values estimated from the observed data is dependent on the quality of the observed data and length of available record. - 6 - Step 8: Create a column with the return period (Tr) for each discharge using Excel formula {(n+1)/m}. Data from 74 flow gauging stations and inflows to dams were used in the regionalisation, with the distribution of stations as shown in Fig. As part of the development of the Joint Peak-Volume (JPV) methodology, Görgens (2007) developed a regionalised index flood approach to design flood estimation for South Africa. (2000), Görgens (2007) and Haile (2011). The distribution of the length of record of the selected gauges used in the analysis is shown in Fig. Video documentary on the devastating floods in Durban in KZN, South Africa in September of 1987. The KZN government set up a special disaster management task team which visited several areas to assess the damage. Hence both the LP3 and GEV distributions, fitted by L-moments (Hosking, 1990; Hosking and Wallis, 1990), were used to estimate the design floods based on the statistics of the AMS at each selected gauge. These methods should be justified and followed systematically. Its capital is Pietermaritzburg, and its largest city is Durban. Analysis is older than the times of great philosophers like Aristotle and Plato. This approach is known as regional flood frequency analysis (RFFA) and utilises data from several sites to estimate the frequency distribution of floods at each site. J. 1993). From the results for KZN the JPV method, with a regionalised GEV distribution with the veld zone regionalisation, generally gave the best performance when compared to design floods estimated from the annual maximum series extracted from the observed data. internet research Step 5: Analysis and synthesis of data Analyse the data that you have collected, and formulate a report on your findings.