Rainfall Analysis The submission of the Rainfall Analysis WG is contained in Table 3. Table 3 Submission of the Rainfall Analysis WG Topic Deliverable Priority Expected duration of (Years) Starting Time Estimated Funding Required (Rx1000) Requirement Status Ranking A.1.1.1 Spatial and Temporal distribution of available rainfall data Inventory and distribution of available daily and sub-daily rainfall data in South Africa H 1 2013/4 100 - 500 Update/create database of daily and continuously recorded rainfall (location and period of available record), source and availability, i.e. update from SAWS, ARC, , Information of daily rainfall available from MAP map project undertaken by Pegram & Associates. Information on availability and distribution rainfall still needs to be updated 1 A.1.1.2 ARF’s (Convert point rainfall data to catchment rainfall) Updated ARFs for use in Africa H 1-5 Started 100 - 500 Develop and evaluate reduction factors to convert point rainfall to areal rainfall Postgraduate started at CUT Postgraduate study started at Univ. Stellenbosch 5 A.1.1.3 Extend the patched rainfall database Updated daily rainfall database for South Africa H 1-5 2013/4 > 500 Infill missing/ erroneous data from 2000 to present and add to database MAP map project started by Pegram & Associates Output: Daily rainfall 1'x1' gridded surfaces from 1950 MAP surfaces 2
Remotely sensed 3 h rainfalls from 2000 will be corrected and disaggregated Completion: March 2016. A.1.1.4 Assemble existing short duration rainfall data (L) Updated sub-daily rainfall database for South Africa M 1-5 2014 100 - 500 Collate and error check continuously recorded rainfall data 3 Extreme rainfall (T > 200 year) Update envelope of maximum rainfall (Probable Maximum Precipitation) H 1 2014 < 100 Current SANCOLD guidelines for estimation of PMF are dependent on PMP, need to update these for use until AEP related floods used for Recommended and Safety Evaluation floods for dam spillways No update since Wits HRU 1/71 report 7 Estimate design rainfall for T>200 years H 1-3 2014 > 500 recommendations to move to high return period floods for dam designs to T > 200 years, hence need to estimate design rainfall for T > 200 years estimate design rainfall up to T=200 years. Need to extend this to T=106 years 4
Catchment data A.1.2.3 Improve flood data-base for RSA and neighbouring countries. Review and extend relationships for strategic streamflow gauging stations and missing historically measured flood discharges, both at-site and at upstream and downstream gauges. H 3? 2015? >500 1 A.1.2.1 Refine catchment formulas. Review and refine different methods for the calculation of catchment (SCS Lag, Tc , TL, etc.) in South Africa. H 2? 2016? 100-500 Postgraduate study started at UKZN 4 Probabilistic design methods A.1.2.2 Guide for annual exceedence probability distributions for floods. Review different annual exceedance probability distributions for floods and develop a guide for the selection of the most applicable distributions and parameter estimation methods for southern Africa. H 2? 2015? 100-500 2 A.1.2.6 Refine regionalised / pooled Index Flood methods. Refine and extend the application of regionalised/pooled Index Flood methods in southern Africa. H 1-5 2015? > 500 Postgraduate study started at UKZN 1 times discharge
Develop a fully probabilistic Joint Peak-Volume method. Render the existing JPV method fully probabilistic by means of bivariate Copula probability theory and refine its regionalisation. H? 2-3 2015? > 500 1 Extreme design flood methods Modernise and refine the existing SANCOLD Guidelines PMF method. Develop PMP isohyets for southern Africa as per the updated WMO method, refine and regionalise existing empirical minimum storm rainfall losses and implement new refined SUHs. H? 2 2016? 100 - 500 2 1.2.7.1 and 1.2.7.3 (Part 1) Update and refine the RMF method and its regionalisation. Update the Kovacs historical maximum flood peak database with latest flood peak measurements and with a of RMF according to measurable rationales. H? 2 2015? 100-500 Postgraduate study started at Univ. Stellenbosch 1 A.1.2.7.2 Approach 1: Develop annual exceedence probability methodology for extreme floods. By consolidating large annual maximum flood peak samples of about 1000 station-years, according to spatially extensive homogeneous flood regions, high-RI flood peaks, or the RIs of empirically/ H? 3 2015? > 500 1
A.1.2.8.5 and A.1.2.4 Modernise existing Synthetic Unit Hydrographs and related “homogeneous” flood regions. Modernise the Synthetic Unit Hydrographs of HRU 1/72, including re-working of average storm loss relationships and of "homogeneous" regions. H 1-5 2015? > 500 2 A.1.2.8.6 Modernise existing empirical methods for small catchments. Modernise existing empirical procedures for estimation and develop new methods for smaller rural and urban catchments. H < 1 2016 100-500 4 Combined empirical-deterministic-probabilistic methods A.1.3.1 Refinement of existing Joint Peak-Volume method. Refine the existing JPV method on the basis of a new delineation of "homogeneous" regions and dimensionless observed flood hydrographs. H 1-5 2015 > 500 2 A.1.2.7.3 (Part 2) Update QT/QRMF ratios. Re-work QT/RMF ratios on the basis of the outcomes of Research Topics A1.2.2, A1.2.6, A1.2.7.1 and A1.2.7.3 (Part1). H 1-5 2016? > 500 3 A.1.2.7.2 Approach 2: Further develop REFSSA annual exceedance probability Refine and spatially extend the REFSSA method by use of the updated maximum flood database for southern H 2? 2015? 100-500 2
methodology for extreme floods. Africa of Research Topic A.1.2.7.3. A.1.2.5 Refine continuous hydrograph simulation methods. Refine the application of continuous rainfall-runoff modelling (e.g. the ACRU model), including stochastic rainfall inputs, to develop Index Flood growth curves and related confidence levels for different regions of southern Africa. H 1-5 2015? 100-500 Postgraduate study started at UKZN 2 stormwater methods A.1.4.1 Research on urban development impacts pre- and post-development. Combined with Research A.1.2.8.4, do field research on storm runoff coefficient changes when undeveloped are urbanised. H 1-5 2016? 100-500 3
A.1.2.7.3: Update Kovacs historical maximum peak database Updated historical maximum peak database H 0.5 2015 100 - 500 Ensure that catchment sizes ranging from 10 km2 to 20 000 km2 are adequately represented in database. List three highest flood peaks at each site. DWA have started with a flood catalogue of three highest recorded flood peaks at selected dams and flow gauging stations. 3 Use output of research topic A.1.2.3 A.1.2.7: Compile palaeoflood database Estimates of flood discharges based on indicators L 1 - 5 2016 > 500 Initiate a systematic research project to obtain palaeoflood records for the larger rivers in RSA 4 Products Used For Flood Estimation The submission of the Products WG is contained in Table 6. Table 6 Submission of the Products WG Topic Deliverable Priority Expected duration of Study (Years) Starting Time Estimated Funding Required (Rx1000) Requirement Status Ranking
C.4 Updated catalogue of recorded maximum flood peaks Catalogue/ database of maximum flood peaks (Based on the results from the Floods WG; "A1.2.3 Review and extension of rating tables at strategic stations") H < 2 2016 < 500 Successful completion of Floods WG Item A1.2.3 - 1 C.5 “Catalogue” of large-area extreme storm isohyetal maps Catalogue/ database of large-area extreme storms similar to information as contained in WRC Report 1420/2/07 M < 3 2016 > 500 A collection large-area extreme storms must be published based on all available data WRC Report 1420/2/07 4 C.6 Web-based GIS database/geodatabase GIS database/geodatabase containing all the relevant spatial feature classes relevant to flood hydrology/ water resources management H < 3 2016 > 500 Create a web-based GIS database which consolidates all the spatial information on climatological variables, catchment geomorphology, channel geomorphology and catchment variables (e.g. geology, soil, and vegetation, SCS hydrological soil groups, veld-type region and Kovacs flood regions) Most of the datasets are available, however defragmented between different disciplines and scientific users. 6