Asian Pacific FRIEND
Intensity Frequency Duration and Flood Frequencies Determination Meeting,
Kuala Lumpur, Malaysia, 6-7 June 2005
Flow Regimes from International Experimental and Network Data
IHP-VI | Technical Documents in Hydrology | No. 5
Regional Steering Committee for Southeast Asia and the Pacific UNESCO Jakarta Office 2005
UHJAK/2005/P/H/1
INTERNATIONAL HYDROLOGICAL PROGRAM
Asian Pacific FRIEND
Intensity Frequency Duration and Flood Frequencies Determination Meeting,
Kuala Lumpur, Malaysia, 6-7 June 2005
Flow Regimes from International Experimental and Network Data
IHP-VI | Technical Documents in Hydrology | No. 5
Regional Steering Committee for Southeast Asia and the Pacific UNESCO Jakarta Office 20025
PREFACE
The Asian Pacific FRIEND (Flow Regimes from International Experimental and Network Data) is an IHP project organized by the IHP Regional Steering Committee for Southeast Asia and the Pacific (RSC SEAP), officially started in 1997. In its first phase the project provided a framework within which research was carried out to improve the understanding of hydrological science and water resources management in the region through comparative studies of the similarity and variability of the regional hydrological occurrences and water resource systems. With the great efforts from nearly 200 members in 5 working groups, significant achievements have been obtained for the phase I of the Asian Pacific FRIEND during the past several years and summarized in the Asian Pacific FRIEND Report for Phase 1 (1997-2001), published in 2002 (IHP V – Technical document in Hydrology No. 9, Regional Steering Committee for Southeast Asia and the Pacific, UNESCO Jakarta Office 2002).
Following several discussions, during the 11th RSC Meeting in Fiji, October 2003 and subsequently during the 12th RSC Meeting in Adelaide, November 2004, it was decided that themes such as high flows and low flows (including droughts) should be continued from phase 1 to phase 2 of the project.
In particular, being rainfall both an essential input to high flow, low flow and drought analysis and a priority in many countries, it was proposed that activities within these themes initially be focused on rainfall, specifically in terms of a) what data are available in countries, b) how accessible is the data for research within each country, c) how accessible is the data for research outside the country, d) availability and origin of design rainfall guidelines/standards in countries and e) investigate development of regionally consistent rainfall design techniques and guidelines.
The Committee therefore decided that in order to progress with the phase 2 plan, each country should provide input on availability of data both within and between the countries, the source organizations and finally the design guidelines/standards and analysis techniques used by the countries.
The present report summarizes the activities carried out in the initial stage of the Asia Pacific FRIEND phase 2, and the results presented at the “Intensity Frequency Duration and Flood Frequencies Determination Meeting” held in the Regional Humid Tropic Hydrology and Water Resources Centre for Southeast Asia and the Pacific (HTC) in Kuala Lumpur, 6 and 7 June 2005.
Giuseppe Arduino Programme Specialist in Hydrological/Geological Sciences,
UNESCO Office, Jakarta
PREFACE
CONTENTS
OPENINGS ……… 1
1. ACCEPTANCE OF AGENDA ……… 1
2. ELECTION OF RAPPORTEUR ………. 1
3. COUNTRY REPORTS ……….. 1
New Zealand ... 2
Japan ... 2
Malaysia ... 3
Viet Nam ... 3
Republic of Korea ... 3
China ... 4
Indonesia ... 4
Philippines ... 4
Australia ... 5
4. WORKSHOP SESSIONS ON IFD AND FREQUENCY DETERMINATIONS ……….. 6
5. REPORTING BACK TO MAIN GROUP ……… 6
Design Rainfall ... 6
Design Flood ... 8
6. DISCUSSION ON NEED AND TECHNIQUES FOR USE OF DESIGN RAINFALL IN FLOOD DETERMINATION ……….. 9
7. DISCUSSION ON NEED FOR LOW FLOW FREQUENCY DETERMINATION AND RELEVANT RAINFALL AND STREAM FLOW INFORMATION ………. 9
8. REVIEW OF RIVER CATALOGUE AND RECOMMENDATIONS FOR IMPROVEMENTS ……… 10
9. TIME LINE ACTION FOR 2006 ……….. 10
10. CLOSING REMARKS ……… 11
ANNEXES
ANNEX 1: List of participants
ANNEX 2: Agenda of UNESCO AP FRIEND 2: Intensity Frequency Duration and Flood Frequencies Determination Meeting, HTC Kuala Lumpur, Malaysia – 6th –7th June 2005 ANNEX 3: Presentation and Country Reports
ANNEX 4: Fifth Year Review of the Catalogue of Rivers for Southeast Asia and the Pacific
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UNESCO APFRIEND MEETING
Intensity Frequency Duration and Flood Frequencies Determination Meeting Kuala Lumpur 6th and 7th June 2005
1. OPENINGS
Mohammed Nor opened the meeting on behalf of Keizrul Abdullah, who was not able to be present due to an important commitment.
Giuseppe Arduino welcomed all participants (Annex 1) on behalf of UNESCO. He recalled the APFRIEND background, such as it began in 1997 and ended with 1st phase in 2002 with a comprehensive report. He also recalled the importance of this meeting both for phase II and for the compilation of a comprehensive regional Asian Pacific chapter to be included in the global FRIEND report that will be presented in the next FRIEND conference, Cuba, November 2006.
Trevor Daniell, Asia Pacific FRIEND Chairman, welcomed the participants and spoke on the attempt to emphasise flood aspects and the trend to forget droughts which are presently affecting this region. He also referred to climate changes where there is evidence that this affects rainfall distributions and intensities spatially and temporally. He was looking forward to see how countries are progressing in terms of design for rainfall or droughts.
2. ACCEPTANCE OF AGENDA
The agenda was accepted as proposed before the meeting (Annex 2)
3. ELECTION OF RAPPORTEUR Mr. Arduino was elected rapporteur.
4. COUNTRY REPORTS
These reports are expected to give a statement of the techniques that are used in each country that attended, whether there are manuals to assist designers and practitioners, the research that is progressing and the data that is available to this APFRIEND project.
Approximately 15 to 20 minutes of presentation and questions was devoted to each country.
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4.1 New Zealand
Mr. Craig Thompson from New Zealand presented High Intensity Rainfall & Flood Frequency Research in New Zealand. The report was divided into 2 parts, with the first part outlining the HIRDS project (High Intensity Rainfall Design System), on which he has worked extensively in the past years and the second part drawing on the work of Charles Pearson and Alistair McKerchar on revision of flood frequencies.
His report is in Annex 3 and included:
- Rainfall index
- Regional Growth Curves (rainfall frequency analysis – Spatially distributed a/U and k – Regional growth curves)
- Reverse engineering of HIRDS
- Where to from here with HIRDS? (web-based application – method improvements – database updates
- Revision of flood frequencies (in progress) which includes a) for a river location, the probability distribution of flood peaks is a basic characteristic, b) historical flood information (augment continuous flood record with historical flood information - data, data range only, etc.) c) two components extreme value distribution d) climate impacts on flood frequencies? Interdecal Pacific Oscillation index (presents a graph with 2 max positives and 1 negative).
Trevor Daniell made a comment on the IPO in that it was being reviewed as part of Australian Rainfall and Runoff. He will present further information in his report (Australia).
4.2 Japan
Mr. Kaoru Takara reported on the Japanese situation on IDF procedures. In 2004 a questionnaire was sent to 47 prefectures (local government). Each local government replied on data availability, updating, IDF curves, probability distribution. A total of 14 questions were submitted to the 47 prefectures. The Takara Report included in Annex 3 commented on:
- Who is using IDF curves; and - The analysis for IDF.
Question from Daniell how do you use IDFs for storm water drainage?
The reply was such that individual prefectures used their IDFs for storm water and was considered to be part of the general river system.
Question from Tabios III. About the gamma 3 parameters. Takara replied that normally they use Log-normal and Gumbel method.
Trevor asks whether there is any push to use a method that would run all over Japan.
Takara stated that individual prefectures would be very reluctant to give up their control on IDFs as these affected development proposals.
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4.3 Malaysia
Mr. Mohd Nor reported on Intensity Frequency duration and flood frequencies.
The report included:
- Introduction
- Hydrological network of Malaysia - Intensity flood duration method - Flood frequency method
- MASMA (intensity frequency duration) - Report and papers
- Q & A
Reports on the reply to the questionnaire given by Trevor on station types and numbers, etc.
4.4 Viet Nam
Mr Tuyen presented his report on Zoning Rainfall Intensity of Viet Nam, which includes:
- Outline of zoning rainfall intensity in Viet Nam
- 159 meteorological stations (1 every 2,076 km2, 50 % from 1961, others from 1976 to present) in the 1980s IMH carried out zoning rainfall intensity for VietNam - Rainfall intensity from 60 recording rainfall stations, longest series of 20 years - Zoning schematisation for rainfall intensity having different ψ (t) curves - Proposed developing IDF for VietNam
- Case study area (central Viet Nam) – river short and steep – affected by typhoons – The rainfall Intensity was Extremely high –
- It is imperative that an extensive study on IDFs progresses in VietNam due to the large increase in Industrial zones, new towns and urbanisation.. Some information was presented on historical floods in 1999.
4.5 Republic of Korea
Mr Samhee Lee reported on IFD Design Procedures in Rep. of Korea. A comprehensive report on the process in Vietnam was presented and is detailed in Appendix 3. It includes:
- Introduction
- Procedures for rainfall frequency by examining many different distributions (Normal – lognormal - gamma – log Pearson type – GEV – log Gumble – Weibul – Wakeby etc.) Details of the monitoring network (5 major rives and 857 rainfall stations) were included
- The frequency analysis of Rainfall Data FARD (developed in 1998 by the Ministry of Government administration and Home Affairs – National Institute for disaster prevention) –The version FARD 2002 has improved the analyses included
- Details of flood frequency
- Summary (reliability of the data – frequency analysis techniques should be integrated in a computer programme – FARD will continuously be upgraded).
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Mr. Soontak Lee added that this programme is mainly used for assessment problems.
There are no rules provided by the country; each private company or institutes analyse on a case by case study according to the needs.
Discussion followed on the different evaluation methods in the different countries.
4.6 China
Mr. Chen presented the National Report from China, which included (Annex 3):
- Data availability in China (3 sources)
- Data intervals most in paper (year books) some in digital forms. Stations from the Ministry of Water Resources 2334 in 1955 to 20566 in 1984 (62% automatic)
- Difficulties for collecting data (difficult to obtain from organisation outside the Ministry of Water Resources)
- Intensity Frequency Duration Design Procedure - Intensity – Duration – Return Period (other IFD terms)
- Formal Design Procedure such as regulation for calculating design floods of water resources and hydrological power projects (1978, 1993) regulation of hydrologic computation of water resources and hydropower projects (2002), various text books.
Empirical methods also available on 24 hrs daily max per year for small basin (small basin in China = area less then 100 km2)
- IFD determination procedures based on homogeneous regions (regionalisation for different rainfall stations with observed data in homogeneous areas)
- The Determination of IFD for ungauged catchments is done by a regional approach.
4.7 Indonesia
Mr Agung Bagiawan presented Intensity Duration Frequency in Indonesia
- General information (geography). Rainfall patterns can be divided in 3 types, such as equatorial, monsoon and local
- IDF used in rational methods to determine the average rainfall intensity for a selected time concentration
- Rainfall data published by BMG (Agency for Meteorology and Geophysics) are daily.
- Number of hydrologic stations - Design flood for Java Island
- Water and soil conservation project in Bengawan Solo
- A national manual for flood design from Public Works is due to be published in the near future and will be distributed to all the provinces.
4.8 Philippines
Mr Guillermo Tabios presented the Intensity Frequency Duration report, on:
- Data availability from the Philippine Atmospheric, Geophysical and Astronomic Services Administration (PAGASA). 10 min intervals (38 stations) 15 min, hrs and daily (over 50 stations)
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- Stream flow data from the Bureau of research Standards of the Dept. of Public Works and Highways and other agencies such as MWSS (water supply) NAPOCOR (hydropower generation), etc.
- Rainfall intensity duration-frequency (RIDF) studies from different institutions (PAGASA in 1981 published RIDF curves for about 50 stations)
- Flood control and Sabo Engineering Centre (FCSEC) of DPWH recently published RIDF analysis of 1-day rainfall of selected stations
- Flood frequency studies. The National Water Resources Council from 1977 to 1981 produced reports on flood studies for the different regions (12 total in the country).
4.9 Australia
Mr Trevor Daniell presented the Design Rainfall Approach, which included:
- Schematic illustration of the design event approach (inputs – model – outputs) - Schematic illustration of the joint probability approach
- Two Volumes were published on flood estimation procedures in 1988, republished in 1997 (Australian Rainfall and Runoff) and is being reviewed and will be published on a continuous basis as individual books are reviewed.
- Modelling - Basic data set
- Computerised Design IFD Rainfall System (CDIRS) - AUS IFD
- A pilot study - Deriving ARI estimates (Dorte Jacob et al, 2005) close to Brisbane - Regionalisation approaches
- Summary - References.
Questions: from Tabios on L moment and L-skewness.
It is recognized that more than one probability distribution family may be consistent with any flood data. One approach to deal with this problem is to select the distribution family on the basis of best overall fit to a range of catchments within a region or landscape space.
One approach for assessing overall goodness of fit is based on the use of L moment diagrams which was done in the Chapter 4 of the APFRIEND Phase 1 Report (2002).
Question From Kaoru, what is LH Moment? Answer explained that when the selected probability model does not adequately fit all the data the lower flows might exert undue influence on the fit and give insufficient weight to the higher flows, which are the principal object of interest. To deal with this situation Q. J. Wang (1997) introduced a generalization of L moments called LH moments, which are based on linear combinations of higher order-statistics. A shift parameter η=0,1,2,3 is introduced to give more emphasis on higher ranked flows.
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5. WORKSHOP SESSIONS ON IFD AND FREQUENCY DETERMINATIONS The participants split into two separate groups to come up with a research plan for each of IFD and Frequency determination. This should address structure, techniques, time frames, and data needs. Four steps to discuss:
1. Developing a process for rainfall and flood frequency analysis;
2. Regional process applicable;
3. Quality control of data; and
4. Software and techniques that could be exchanged.
The above topics will be discussed under the following headings:
1. Design Flood; and 2. Design Rainfall.
6. REPORTING BACK TO MAIN GROUP 6.1 Design Rainfall
China, Indonesia, Japan, Rep. of Korea, Malaysia, New Zealand, Viet Nam participated in this group.
1. Developing a process for rainfall and flood frequency analysis;
2. Regional process applicable;
3. Quality control of data; and
4. Software and techniques that could be exchanged.
6.1.1 Developing a process for design rainfall
We may propose a procedure after doing some comparative study described below.
6.1.2 Regional process applicable
In order to check applicability of each country’s method or some kinds of software for the intensity-duration-frequency (IDF) analysis, the group proposes a comparative study in the region as an Asian Pacific FRIEND (APF) project. The study includes:
a. Data exchange (By September 2005): Rainfall data at least three sites (or catchments) should be submitted to the group from each country. Data requirements are:
(1) The durations of rainfall should be 10 min to 72 h.
(2) Annual maximum rainfall series (AMS) should be provided. If 10-min rainfall data series are available, they can be used for the partial duration series (PDS) or the peaks-over-threshold (POT) approach.
b. Application of each country’s method/software using the data provided (October 2005 to February 2006).
c. Comparison of the results (March to June 2006): The results of comparative study conducted by each member should be discussed at a meeting during the year 2006. The study focuses are:
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(1) Performance/parameter values of the IDF curves (2) Rainfall characteristics in terms of the IDF
d. Applicability of the IDF method will be discussed and development of a process for design rainfall that may be commonly used in the Southeast Asia and the Pacific region.
6.1.3 Quality control of data
This issue is basically very difficult to overcome. Bad quality data are ones of heavy events with shorter durations. Missing data and outliers are also problems. The quality control should be discussed in the whole APF team.
6.1.4 Software and technics exchanges
Some countries in the region already have a package of software to deal with frequency and IDF analyses: for example, SMADA (Indonesia), FARD (Rep. of Korea), HIRDS (New Zealand). These packages are used for the design rainfall research by each country.
6.1.5 Other issues
The following issues were raised:
a. Point rainfall versus areal rainfall: Point rainfall data are often used for IDF analysis.
Areal average rainfall is also useful. Area reduction factor would be one of the research themes.
b. Shortage of data: To overcome the shortage of data, PDS (POT) analysis and regionalization techniques are recommended.
c. The interdecadal Pacific oscillation (IOP) is another possible issue to be considered in the design rainfall and flood.
6.1.6 Plan
Plan for the future is to take at least 3 example sites per country on daily data (possibly hourly data) to be shared by countries and to be used with different techniques of at-site frequency analysis. The data need to be forwarded to Mr Guillermo Tabios.
The plan deadlines are:
- Before the end of June 2005 for data provided to Mr Tabios gtabios@up.edu.ph (station name, location, elevation, coordinates, station type, raw time series data as a preference or annual maximum series over a range duration of 6 min through to 72 hours, of length of record as long as possible). Acceptable formats include flat ASCII files, excel format or other suitable formats.
- Data exchange will be made to countries as soon as possible (from Mr Tabios) - Individual countries representatives from Indonesia (Agung Bagiawan), Japan
(Kaoru Takara), China (Chen), Viet Nam (Tuyen), New Zealand (Craig Thompson),
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Philippines (Tabios), Malaysia (Nor), Australia (Trevor Daniell or Ross James) Rep. of Korea (Hong Kee Jee hkjee@yu.ac.kr) will use the provided data in their own models and produce results and reports both in table and graph forms by 15 September 2005 to Trevor Daniell (or alternatively to Mr Tabios or Mr Thompson).
- A comparison will then be made of the results and recommendations on the various techniques applied.
- abstract for the Cuba FRIEND Conference by September 2005 (Mr Trevor Daniell) - paper report (chapter) for the Cuba FRIEND Conference by June 2006.
6.2 Design Flood
Philippines, Australia, Rep. of Korea and Malaysia participated in this group to address the following points:
1. Developing a process for design flood analysis including flood frequency analysis;
2. Regional processes that were applicable to design flood estimation (eg Flood frequency analysis);
3. Quality control of data; and
4. Software and techniques that could be exchanged
6.2.1 Concerning points 1 and 2 the following table was prepared Type of
catchment
Location Small catch.
<100 km2
Medium catch.
> 100 ÷ <500
Large catch.
> 500 km2
Gauged Rural Probabilistic Rm.
If data available then flood Frequency analysis
Rm-R/R If data available then flood Frequency analysis
Full R/R model If data available then flood Frequency analysis
Urban Probabilistic Rm
If data available then flood Frequency analysis
Rm-R/R Full R/R model
Ungauged Rural Regionalised/empirical
Method
If data available then flood Frequency analysis
Rainfall/Runoff with regional Rainfall design and Index Flood Method
Rainfall/Runoff with regional Rainfall design and Index Flood Method
Urban Regional Rainfall and rational method If data available then flood Frequency analysis
Rainfall/Runoff with regional Rainfall design
Rainfall/Runoff with regional Rainfall design
Legend Rm Runoff modelling, -R/R Rainfall Runoff Modelling
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6.2.2 Processes for flood design estimation and quality control Type Data Series of data
to be used
Improving fit of peak data
Choice of Probability distribution Gauged - Observed WL
(peak levels, historic information) - observed flows Watch out for land use changes, stationarity of records
Selection of annual series or partial series or POT (selection to ensure of
independent events)
- Historical information, - Outlier data (censoring low flow data) Non
homogenity/mixed distribution (eg IPO + IPO-)
- GEV
- Log Normal, - LP III, - Generalised Pareto - Exponential, - P III
Etc.
6.2.3 Regionalisation
Flow Index method – choice between Mean Q and Median Q Qt/Qmean median = ψt
Regression Method - regionalise parameters of probability distribution a function of drainage area, annual mean rainfall, slope, length of channel, etc.
6.2.4 Plan
Development of a plan with illustrative examples in each country on the topics assessed above. The schedule has been agreed as follows:
- By the end of June 2005 Mr Trevor Daniell will provide a detailed plan for activities to be carried out to design flood group.
7. DISCUSSION ON NEED AND TECHNIQUES FOR USE OF DESIGN RAINFALL IN FLOOD DETERMINATION
Agreed on two sections, such as:
- Techniques and models used, and
- previous studies carried out in each country.
8. DISCUSSION ON NEED FOR LOW FLOW FREQUENCY DETERMINATION AND RELEVANT RAINFALL AND STREAMFLOW INFORMATION
Countries were then asked on the need and procedures used for low flow analyses:
- Indonesia - by the end of 2005 a drought map will be available
- Japan, research using low flow duration curve and groundwater flow across many of the prefectures but this is left up to individual prefectures
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- China has conducted extensive analyses of low flows both at provincial and national government level and is considered to be a priority in some catchments such as the Yellow River Catchment. There are projects looking at researching river systems where zero flow occurs.
- Viet Nam, research on low flows in term of drought and water supply in dry season (irrigation)
- New Zealand, 2 approaches done, 1) drought severity index and 2) extreme analyses on low flows. In conjunction with the meteorological aspects, soil moisture deficit analysis has been used.
- Philippines, several documents done for the 12 regions (1985), low flow frequency analysis and frequency duration which also includes drought analysis based on runs analyses
- Malaysia, 2 methods,
- 1) on line drought severity indexes; and - 2) HP12 for low flow investigation
- Australia, many different methods are used depending on individual States and research organisations. Drought investigations have become extremely important across Australia both for Agricultural areas and city water supplies with the majority of Australian large cities on Water Restrictions eg Sydney, Canberra, Adelaide, Perth, Melbourne.
- Rep. of Korea, methods used by individual institutions/Ministries on low flow analysis, very limited publications available.
A follow up questionnaire on low flows and rainfall methods for drought index methods is to be developed. It was noted that a Workshop on Low flow methods would be presented by European researchers in Kuala Lumpur later this year based on researchers experience in Norway, Germany and Netherlands. (Mohd Nor has the details for this workshop)
9. REVIEW OF RIVER CATALOGUE AND RECOMMENDATIONS FOR IMPROVEMENTS
Trevor Daniell presented the Catalogue revision made by himself, Yasuto Tachikawa and Soontak Lee. A revised version will be disseminated to all National IHP committees and members present at this Workshop.
Some comments were made on the report and these will be taken note of in producing the draft for distribution.
10. TIME LINE ACTION FOR 2006
Actions to be taken refer to paragraphs 5 and 6.
At the 13th RSC Meeting in Bali, Mr Tabios will present the draft of the design rainfall and design floods to the APFRIEND TSC Meeting, as Chairman Daniell will be at a FRIEND meeting in Montpellier.
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11. CLOSING REMARKS
Mr. Daniell thanked all participants for attending and their active participation in discussions and the contribution of processes used in each country. He emphasized the need for all to participate actively in the activities decided at this workshop meeting and gave a plead to all countries to “ Please send data as soon as you go back to your country!!!!!!!!”
He thanked the HTC for having organized the facilities and the participation of the Malaysian Delegates.
The minutes and presentation will be published in an APFRIEND UNESCO Office Jakarta Technical document. All participants are reminded to develop a small paper outlining their contribution to the workshop in addition to the Power point presentations given.
ANNEX 1:
List of Participants
No Family Name(s) First name Country Institution Funding
sources E-mail Fax Number Nights
1 DANIELL Trevor AUSTRALIA
Centre for Applied Modelling in Water Engineering, School of
Civil and Environmental Engineering, The University of
Adelaide, Australia, 5005
UNESCO trevord@civeng.adelaide.edu.au Ph +618 8303 5454 Fax
+618 83034359 3 (5-6-7 June)
2 CHEN Yuanfang CHINA
Head Department of Hydrology and Water Resources Hohai University
UNESCO yfchen@mail.edu.cn
Fax 0086-25-83735375 or 83787364 or 0086-25- 83708419
3 (5-6-7 June)
3 BAGIAWAN Agung Indonesia
Experimental Station for Hydrology Research Institute for
Water Resources
UNESCO bagiawan@bdg.centrin.net.id
Telp. +6222-2503357 Fax
+6222-2503357 or 2500163 3 (5-6-7 June)
4 LEE Samhee KOREA
(REP. OF)
Korea Institute of Construction Technology, 2311, Daewha- dong, Ilsan-gu, Goyang-si, Gyeonggi-do, 411-712, Korea
UNESCO samhee.lee@kict.re.kr (Tel) 82319100261 (Fax) 82319100251
4 (4-5-6-7 June)
5 LEE Soontak KOREA
(REP. OF)
School of Civil and Environmental Engineering Yeungnam University 214-1 Daedong, Kyongsan, Daegu 12- 749 Republic of Korea
UNESCO
leest@yu.ac.kr;
soontaklee@hanafos.com
Tel. +82-53-810-2412 / +82- 53-656-2525 Fax +82- 53-813-4032 / +82-53-656- 2580
4 (4-5-6-7 June)
6 TAKARA Kaoru Japan
Vice Director, Disaster Prevention Research Institute (DPRI), Kyoto University, Uji, Kyoto 611-0011, Japan
UNESCO takara@mbox.kudpc.kyoto-u.ac.jp;
takara@flood.dpri.kyoto-u.ac.jp
Phone: +81-774-38-4125
FAX: +81-774-38-4130 2 (5-6 June)
7 THOMPSON Craig New Zealand
Group Manager, Climate Services National Inst. of Water &
Atmosphere Res. Ltd (NIWA)
UNESCO c.thompson@niwa.co.nz Tel: (+64 4) 386 0494 Fax: (+64 4) 386 0341
4 (4-5-6-7 June)
8 TABIOS Guillermo PHILIPPINES
Assoc Professor and Chair, Dept of Civil Engg & Research Fellow, Nat'l Hydraulic Research Ctr Univ of the Philippines, Diliman, Quezon City
UNESCO gtabios@up.edu.ph Phone (632)927-7176/925-
6991 Fax 927-7190 3 (5-6-7 June) UNESCO APFRIEND WORKSHOP
(The Humid Tropic Centre, Kuala Lumpur, Malaysia, 6-7 June 2005)
No Family Name(s) First name Country Institution Funding
sources E-mail Fax Number Nights
UNESCO APFRIEND WORKSHOP
(The Humid Tropic Centre, Kuala Lumpur, Malaysia, 6-7 June 2005)
9 HOANG Tuyen Minh VIET NAM IMH, Hanoi Vietnam UNESCO hmtuyen@vkttv.edu.vn (84 4) 835 5993 3 (5-6-7 June)
10 ARDUINO Giuseppe ITALY UNESCO Jakarta UNESCO g.arduino@unesco.org Tel. +62 21 7399 818; Fax +62
21 72796489 2 (5-6 June)
ANNEX 2:
Agenda of UNESCO AP FRIEND 2: Intensity Frequency Duration and Flood Frequencies Determination Meeting,
HTC Kuala Lumpur, Malaysia.
6
th– 7
thJune 2005
Date Agenda Time DAY 1
6th June 2005
1. Welcoming Speech by Datuk Ir. Hj.
Keizrul bin Abdullah
2. Opening Remarks by Dr. Giuseppe Arduino & Prof. Trevor Daniell 3. Election of Rapporteur
4. Country Reports 4.1 New Zealand 4.2 Japan 4.3 Malaysia 4.4 Vietnam TEA BREAK
4.5 Republic of Korea 4.6 China
4.7 Indonesia 4.8 Philippines 4.9 Australia
Discussion and forming 2 groups i.e. IFD
& Frequency Determination LUNCH 5. Workshop Sessions
GROUP 1: IFD
GROUP 2 : FREQUENCY DETERMINATION
- to come up with a research plan.
This should address structure, techniques, time frames and data needs.
TEA BREAK 6. Groups reporting END OF DAY 1
9.00 am -9.20 am
9.20 am - 9.25 am 9.25 am - 9.30 am 9.30 am - 9.35 am
9.35 am - 9.50 am 9.50 am - 10.05 am 10.05 am - 10.20 am 10.20 am - 10.35 am 10.35 am - 10.50 am
10.50 am - 11.00 am 11.00 am - 11.15 am 11.15 am - 11.30 am 11.30 pm - 11.45 pm 11.45 pm - 12.00 pm 12.00 pm – 12.45 pm 12.45 pm - 2.00 pm 2.00 pm - 4.15 pm
4.15 pm - 4.30 pm 4.30 pm - 5.30 pm
Date Agenda Time
DAY 2
7th June 2005
– Recap of Day 1
7. Discussion on needs and techniques for use of IFDs in flood determination
- Modelling
- Frequency determination
8. Discussion on needs for low flow
frequency determination and relevant rainfall and streamflow information.
9. Review of river catalogue and recommendations for improvement
LUNCH 10. Report summary
11. Time line action for 2006 by Prof.
Trevor Daniell
12. Closing remarks by
Dr. Mohd Nor bin Mohd. Desa TEA BREAK END OF DAY 2 FREE AFTERNOON
8.30 am - 9.00 am
9.00 am - 10.30 am
10.30 am -11.30 am
11.30 am - 1.00 pm
1.00 pm - 2.00 pm 2.00 pm - 3.00 pm 3.00 pm - 3.10 pm
3.10 pm
Dinner will be held at the KLCT on 6th June 2005 at 8.00 pm AGENDA : UNESCO AP FRIEND 2 Intensity Frequency Duration and Flood Frequencies Determination Meeting
HTC Kuala Lumpur - 6th– 7th June 2005
ANNEX 3:
Country Report and Presentation
1. New Zealand ... 1
2. Japan ... 11
3. Malaysia ... 17
4. Viet Nam ... 33
5. Republic of Korea ... 43
6. China ... 61
7. Indonesia ... 67
8. Philippines ... 79
9. Australia ... 111
Country Report – New Zealand -1-
High Intensity Rainfall and Flood Frequency Research in New Zealand For UNESCO APFRIEND WORKSHOP
Kuala Lumpur 6-7 June 2005
Craig Thompson National Institute of Water and Atmospheric Research Wellington, New Zealand 14 June 2005 Thank you for the opportunity to attend the UNESCO APFRIEND Workshop in Kuala Lumpur from 6-7 June 2005. A write-up of the presentation I made to the Workshop is appended below and outlines the current state of research in design rainfall and flood estimation in New Zealand. This note is in two parts and outlines the research undertaken by NIWA scientists on (a) high intensity rainfall and (b) on regional flood frequency research. I acknowledge the contributions of two of my colleagues, Charles Pearson and Alistair McKerchar, in providing material for the presentation.
This presentation is in two parts and outlines the research undertaken by NIWA scientists on (a) high intensity rainfall, and (b) on regional flood frequency research.
HIRDS: High Intensity Rainfall Design System (by Craig Thompson)
HIRDS is a procedure for estimating rainfall frequency at any point in New Zealand.
Such procedures have two purposes: the estimation of rainfall depths for design purposes, and the assessment of the rarity of observed rainfalls. In 2001 the design rainfalls for New Zealand were more the 20-years old; the existing design rainfalls treated New Zealand as a single “homogeneous region”; there had been a large increase in the rainfall data available, and there were new statistical methods and mapping techniques that could be investigated.
The approach taken in HIRDS was to use regional frequency analysis that includes mapping an index-rainfall. (Full details of the method can be found in Thompson, 2002.) New Zealand annual maximum series for 10 standard durations from 10 minutes to 72 hours were extracted from NIWA’s Climate Database and Water Resources Archive, together with data held separately by New Zealand’s regional authorities. Longer data records mean that for some sites at least, the high intensity rainfall estimates will be more precisely determined than before, with smaller associated standard errors. Additionally a large number of extreme rainfall events have also occurred that need to be accounted for in the statistics.
In regional frequency analysis, the components involve mapping an index (the median annual maximum) rainfall, and regional rainfall growth curves that are ratios of the T- year rainfall depth to the index rainfall, and are common to every site in the region.
The method assumes that locations within some defined region can be combined in such a way as to produce a single rainfall growth curve that can be used anywhere in that region. All sites are expected to have similar frequency distributions, but the implied assumption of homogeneity is seldom satisfied exactly. Although fixed regions have commonly been used to develop rainfall growth curves, a recent approach based on a “region of influence” can be defined for each rainfall site, thus
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avoiding problems at the boundaries between regions. By pooling rainfall sites within some defined region can provide reliable and robust estimation of regional growth curves. In HIRDS, the region of influence approach was used to develop the rainfall growth curves from a frequency analysis of the pooled data. Sites were selected isotropically within a 60km radius of the site of interest, and is a compromise between the possibility of selecting sites from a different rainfall climate and the inclusion of too few sites.
In HIRDS the index rainfall was taken to be the median annual maximum rainfall.
The median has an aep of 0.5, corresponding to an average recurrence interval of 2- years. The median is used since it is not usually affected by the skewness of the distribution or by the presence of outliers. A minimum length of 10 years (5 years in the mountains of New Zealand) of data ensures, that at most locations the median is reasonably well estimated. The mapping of the index rainfall involved fitting trivariate thin-plate smoothing splines as implemented by ANUSPLIN (Hutchinson, 2000). The three independent variables in the fitting were longitude, latitude and elevation. The trivariate spline is well suited to applications over complex terrain as is found in New Zealand, and can provide a robust method of surface fitting meteorological data from moderately sparse data networks. Four of the ten storm durations (10 minute, 1, 24 and 72 hour) were mapped with ANUSPLIN on a 0.05º longitude/latitude digital elevation model with a constant signal to error ratio of 4:1 to maintain consistency between the fitted surfaces. For the other storm durations, depth-duration ratios were evaluated from the station data.
The other component in the regional frequency relation is the rainfall growth curve.
Growth curves are standardised and dimensionless, enabling the estimation of extreme rainfalls of any specified ARI relative to the median rainfall. Inverse cumulative distribution functions are the basis of growth curves, and a three- parameter generalised extreme value distribution (GEV), combined with regionally weighted probability weighted moment estimation of is parameters was used to evaluate regional growth curves for New Zealand. For a given average recurrence interval, T, a dimensionless regional growth curve, relative to the index rainfall for New Zealand is:
1 ) ) (
( ) 1 2 ( / ) ( )
( 2
2
+ + −
=
= Y Y
Y U a
U x a
T x T
g T
Regional growth curves depend directly ona U and, k through the reduced variate term YT. a U varies over New Zealand from about 0.2 to 0.5. The growth curves are more sensitive to a U than to the shape parameter; the larger a U becomes, the larger the magnitude of the growth curve relative to the median and vice versa.
Moreover, a U which is the ratio of dispersion (or standard deviation) to the mode can be thought of being like a "coefficient of variation". Thin-plate smoothing splines were fitted to the values of a U and k for the standard durations. Diagnostic output from ANUSPLIN indicated that both parameters were largely independent of site elevation and depend only on geographical position.
In the presentation, examples of mapped median rainfall, and a Uand, kare given to illustrate the underlying methodology in HIRDS. Given user supplied geographic coordinates, the HIRDS will provide a table of design rainfalls in a depth-duration-
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frequency format. A sample out for Queenstown New Zealand (45.033°S, 168.667°E) is given below.
The final part of the talk discussed future develops in HIRDS, including improved regional growth curve estimation, accounting for non-stationary aspects of climate and climate shifts, and incorporation of update databases to account for newly recorded extremes of rainfall that had occurred since the previous update.
Revision of New Zealand Flood Frequency: Work in Progress (Charles Pearson and Alistair McKerchar, National Institute of Water and Atmosphere, Christchurch, New Zealand)
The revision of the design floods in New Zealand is new research lasting until June 2008. Key features of this project include drawing on and extending the work of two previous nationwide studies undertaken by Beable and McKerchar (1982), and McKerchar and Pearson (1989). The new study will (a) make use of nearly 20 more years of flood peak flow data (b) map flow frequencies on river drainage networks through the use of rainfall-runoff models and design rainfalls such as HIRDS, (c) account for climate variability and other non-stationary aspects of climate, and (d) recommend design floods for use in flood inundation modelling and mapping.
The Water Resources Archive contains over 400 river flow records that can be analysed for design flood estimation, and is complemented by over 400 flow records held by regional authorities. A number of extreme-value frequency distributions, will be considered, namely the generalised-extreme value distribution including the Gumbel or EV1, the two-component extreme-value distribution, and the generalised pareto distribution, with the parameters of these distributions estimated from L- moments approach. Use of partial duration series, or peaks-over-thresholds, shows that these type of data, when plotted on L-kurtosis versus L-skewness graphs can show a better definition of flood frequency groupings and which frequency distribution to use, than does the scatter-plotting of L-moment ratios of annual
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maxima. Another key aspect of this study will be to augment the flow record with historical flood information from flood marks and other flood levels, from post-event
“slope-area” gauging of rivers, or from the dates of known floods and other anecdotal evidence about floods available in libraries and newspaper archives. In some cases the historical information collected will be able to extend flood information back into the mid and late nineteenth century. Flood frequency distributions will be fitted to all the data that also includes this valuable historical resource.
A new development in the flood frequency analysis in New Zealand has been the use of the two-component extreme value distribution (TCEV). This is a mixture of two EV1, or Gumbel, distributions. For both rainfall and flood extremes, most of New Zealand displays an EV2 frequency distribution, and the TCEV has a property in that it is more conservative than an EV2 in the tail of the distribution. This distribution, fitted to L-moment ratios, has been successfully applied to the east coast of the South Island of New Zealand (Connell and Pearson, 2001). From a physical stand-point, the TCEV allows for two flood-causing processes; the frequent but smaller flood producing events which forms the basic flood series, and an outlier series that result from infrequent but large storms associated with slow moving frontal systems or sub- tropical depressions that pass over New Zealand.
An outcome of the project will be an automated regional flood estimation system for any river system in New Zealand. An example of the type of output is given below.
The procedure is based on mapping and interpolation of river networks between recording sites. Use will be made of a physically-based, distributed rainfall-runoff model (“TopNet”) with design storm rainfalls from HIRDS and long series of daily rainfalls simulated all over New Zealand, to estimate flood flows along river networks, taking care to match the at-site flood estimates. An example of estimating the flood frequency of a river location on a river network is shown below, using the Freshwater Information New Zealand GIS (FINZ) template.
0 1 2 Kilometers
NZReach Easting Northing Map Ref
9.85
RP = 1/aep Q se
2.33 5.0 22%
5 7.4 18%
10 9.3 21%
20 11.2 23%
50 13.6 26%
100 15.5 28%
FINZ Flood Estimate
13043878 Little River @ Bridge
Flood Frequency Table Catchment area km2
2395600 5749600 K35:956496 NZReach
Easting Northing Map Ref
9.85
RP = 1/aep Q se
years m3/s %
2.33 5.0 22%
5 7.0 18%
10 8.7 20%
20 10.3 23%
50 12.4 26%
100 14.0 28%
200 15.5 30%
FINZ Flood Estimate
13043878 Little River @ Bridge
Flood Frequency Table Catchment area km2
2395600 5749600 K35:956496
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An aspect that will be addressed over the next few years in this research project, and incorporated in the flood estimation system is the non-stationary effects of climate on flood frequency. It is known that the Interdecadal Pacific Oscillation and El Niño- Southern Oscillation phenomenon have significant influences on New Zealand’s flood and rainfall regimes in some regions of the country. The Interdecadal Pacific Oscillation is a dominant climate oscillation that has a pronounced signal in the surface temperature of the Pacific Ocean, operating on 20-30 year time scale, which ENSO is tropical atmosphere-oceanic influence operating on a 4-7 year time scale.
As a result of the IPO and ENSO influences, a method will be developed to account for the climate state both in the shorter interannual (ENSO) scale and the longer decadal (IPO) scales. The presentation provided an example for the Waihopai River in the South Island showing how the 100-year flood event changes according to the phase of the IPO. In the negative phase of the IPO the 100-year flood is estimated at 64 m3/s, while in the opposite phase the 100-year flood becomes 134 m3/s, a significant increase in river flow. Alternatively, the 100-year event in the negative phase of the IPO becomes a 3-year estimate in the opposite phase. When designing flood retention systems or underground water infrastructures, the state of the IPO is an important consideration to ensure the most appropriate level of security and safety. In summary, a new concept that will be built into the new flood frequency system is that flood frequency changes with time. For users of the system, their design life ahead for use of flood frequency estimates will need to be overlaid with expected changes in flood frequency over that period of time to obtain the best flood frequency estimates.
The talk concluded by indicating that the project is underway, and will address all the aspects of the talk using existing methods as well as developing new methods to account for non-stationary climate influences, and for the regionalisation of frequency analyses between and within river catchments. It is expected that the project will be completed in June 2008.
References
Beable, ME, and McKerchar, AI, 1982. Regional flood estimation in New Zealand.
Water and Soil Tech. Publ. 20. Ministry of Works and Development, 139 p.
Connell, RJ, and Pearson, CP, 2001. Two-component extreme value distribution applied to Canterbury annual maximum flood peaks. J. Hydrol. (NZ). 40, 105-127.
Hutchinson, MF, 2000. ANUSPLIN Version 4.1 User Guider. Centre for Resource and Environmental studies. The Australian National University, Canberra, 51 p.
McKerchar, AI, and Pearson, CP, 1989. Flood Frequency in New Zealand. Publ. No.
20, Hydrology Centre, Department of Scientific and Industrial Research, Christchurch, 87p.
Thompson CS, 2002. The High Intensity Rainfall Design System: HIRDS.
Proceedings Int. Conf. On Flood Estimation, March 2002, Bern, Switzerland, pp273- 282.
Country Report (Presentation) - New Zealand
High Intensity Rainfall & Flood Frequency Research in New Zealand
Craig Thompson
National Institute of Water and Atmospheric Research Wellington, New Zealand
UNESCO APFRIEND Meeting Kuala Lumpur
6-7 June 2005
Farm buildings cut off by flood waters, southern North Island, 25 Feb 2004.
Motivation and need for revision -In 2001: Design rainfalls for New Zealand
were over 20 years old - New Zealand: single “homogeneous”
region
- Large increase in data
- New statistical methods and mapping techniques
HIRDS: High Intensity Rainfall Design System
NZ annual maximum rainfalls for D=10m to 72h NZ annual maximum rainfalls for D=10m to 72h
Regional Frequency Analysis (Mapped median rainfall and regional growth curve parameters)
Regional Frequency Analysis (Mapped median rainfall and regional growth curve parameters)
Rainfall-depth-duration frequency table, and standard error estimates Rainfall-depth-duration frequency table, and standard error estimates
Data
Underlying method User defined input
Elements of HIRDS
Geographic location Geographic location
Output
40 320
160
80 40 16080 80
80
80
160
80
40
80
160 80
80
80
80
80 160
40 80
1 60
80 80
160 80
80 8 0 80
80
80
80
80
80
80
80
160
80 80 80
80
80 Median Rainfall
<30 30 - 40 40 - 50 50 - 60 60 - 70 70 - 80 80 - 90 90 - 100 100 - 140 140 - 180 180 - 220 220 - 260 260 - 300
Spatially distributed median rainfall (Rmed) for a range of durations (D) Spatially distributed median rainfall (Rmed) for a range of durations (D)
Thin-plate smoothing spline interpolation 0.05° x 0.05° fitted surfaces of Rmedat 10m, 1, 24 & 72h
Thin-plate smoothing spline interpolation 0.05° x 0.05° fitted surfaces of Rmedat 10m, 1, 24 & 72h
Depth-duration ratios linking Rmedat index D to other D
Depth-duration ratios linking Rmedat index D to other D
24 hour median rainfall (mm)
Table of extreme rainfalls with a 2-year ARI Table of extreme rainfalls with a 2-year ARI
Index Rainfall Variable
Regional Growth Curves
• Rainfall frequency analysis
– Series standardised by site median rainfall – “Region of influence” approach to regionalisation – 3-parameter GEV distribution fitted to data
• Spatially distributed a/U and k – Mapped with smoothing splines
• Regional growth curves – Are relative to the median – Rgc(T) = f(a/U, k, YT)
Mapped surfaces of GEV parameters:- 24h a/U
0.3
0.32
0.26
0.360.38
0.2 4 0.32
0.26
0.3
0.24 0.32
0.32
0.38
0.32
0.3
0.26
0.26
0.26
0.36 0.3
a/U
< 0.24 0.24 - 0.26 0.26 - 0.28 0.28 - 0.3 0.30 - 0.32 0.32 - 0.34 0.34 - 0.36 0.36 - 0.38
> 0.38
a/U
0
-0.05
-0.3 0.05
-0.2 -0.15
-0.1
-0.1
-0.05
0
-0.05 -0.05
-0.1
0
-0.1
-0.05
-0.1
-0.05
-0.1
-0.05
-0.15
-0 .15 -0.05
-0.1
-0.15
-0.05
-0 .05 0.05
-0.1 -0.15
-0.15 -0 .05
-0.1
-0.1 -0.05
-0.05
-0.05 0 -0.15
-0.1
k
< -0.35 -0.35 - -0.3 -0.3 - -0.25 -0.25 - -0.2 -0.2 - -0.15 -0.15 - -0.1 -0.1 - -0.050 -0.05 - 0 0 - 0.050 0.05 - 0.100
k
1 2) ( )2 / ( 1 ) /
( =+ −Y +
YT Y U a
U T a Rgc
