FLOOD01798

• County: Statewide
• Title: Australian Rainfall and Runoff 1998, Revision of Book VI - Estimation of Large to Extreme Floods
• Date: 11/28/1998
• Prepared By: Rory Nathan, Sinclair Knight Merz
• Floodplain - Doc Type: Educational/Technical/Reference Information

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DRAFT D

5

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6

7

Book VI - Estimation of Large to Extreme Floods

4.5 Oerivalio!l Gf COOlpIete Design f'I(lOd FJtl<lOem:y ClJI'Ye m.umn.n..n....n.nn.._u........n.u........n.......... 35
4.6 Seasonal Design Floods .u.n.nnnnuumun.nn.n.n.unnnunmun......n........mnnu.nnn..n.n.n..n. .mn... 35
4.7 Preliminary Estimates of Design Floods ..uu.uunn.nu.u.u............m..n..n.nunnuunu..u.....uuu.uu.u..36
4.7.1 Preliminary estimates of peak dischargenmnunnmuuuw.......um....wn..u..u.wnu..uwnu 36
4.72 Preliminary estimates of design hydrographs ............nmu.u.uuuu.................n.....u...u... 36
4.8 Estimation of the Probable Maximum Flood......muu...uu.........m..uwmunu.unn...w...n......uun..uuu 36
4.9 Incorporation of Pa1eohydrologicat Estimates unu.u.nunu.......n..n.nnnnn..u.nnu.n....u..uu.....uun..... 37

Additiona I Desig n Co nsiderations........ 'nnu m.. n n u. n....... ,,'n.. nn n .nn n n.n..n n n n n .un n n .w. n. n 37

5.1 General .n.. n. n m.. u...........u..u. u..............u.. u. n .n..u n u u. n n ............m......n n n n u. n.n.. nn.. u.n.. u.u u u 37
5.2 Derivation of Reservoir Outflow Frequency Curves wmnmnn.............nnn.w......U...u.n...nnn..umun. 38
52.1 Importance of reservoir storage and initial drewdown.unuuunnnn..uuunwnu.u.w.n.....m. 38
5.2.2 Approximate methods. representative initial storage content uunmunn.wnmnnuunwnu. 38
52.3 Joint probability analysis of inflow and initial storage volume ....u....unwu....n.w.u.mnn.u 38
5.3 Concurrent Tributary Flows m..nnn.n.m...n.....n.................n..n.nn.m.......u.nn.nuw.....u...........u...... 39
5.3.1 Overviewn u ..... n m............. u...... n.. ...u.......u. u........ n m.. n n m....u n..n. n... n. n.... uu. n n.... uu. 39
5.32 Approximate procedures nun uu. ...w.. n ..u... n. ___.u n nu..............n............... ....... m.. n.' m..... 40
5.4 Consideration of Snowmen .n.....n..m....................................nn..n.n..n.nunuu.n...n.. n..u..n..u.nn.n.. 41
5A 1 Overviewu... n..u ........ n" ....w............. u....... u............. m. w' n...u ..uw.. n...... u... nun ...u n. n n. 41
5.4.2 Selection of snowmelt modeL.......................m.....unu.......u.....nn...u.wu.u...wu..nmn...41
5.4.3 Application to Extreme eventsww..n.....wun.m......uu....uuu....u.....uu..............u.nnu...u.41
5.5 Consideration of Long Duration Events .nm..............u...........u..mnuuu..mu..wu..u..uu..un.uwuumA2
5.6 Treatment of Uncertainty......... n.. n ...uuu u... n. n uu. u.. w un. u.. n ...................... n.............. ...................42
5.6.1 General.. u m. n. n n mu n.. m...................... ........... u'....m .u. nun.u n w.. n... n.... n.u.... n............ 42
5.62 Evaluation of uncertainty ...wun.nnu......n..u....unnnuu......u.uu.....u.........n.....un..wn...n 43

Worked Examples w......................n.u. .u..n.n..w.......un.un.nnnu.................................. .....u......n......44
6.1 The Design Problem w.n.nnuun....nU....n..............U.........nUn...nuuw.......nunnuu....wu..nwn..u..m44
6.2 Derivation of Rainfall Frequency Curves.n.n.....n...n.....unwu.n.........................................................44
6.2.1 Upper limit of extrapolation is 1 in 100 AEP w..uuu.......uu....uu....wu...uuuuu..wu..muuu 44
6.2.2 Upper limit of extrapolation is 1 in 2000 AEP u.u..uu....un....nnuu.uun..wuu..muunuu.n. 46
6.2.3 Estimation of Preliminary PMP Estimates ...........um.u..n..u..muw.....w..un..u...w.....w.... 47
6.3 Derivation of Inflow Flood Frequency Curve ...wwu..uuwnu.uu...u.n..................nw....wu.........n..uA7
6.3.1 Selection of design parameters....u...u.............................nn.u.......u..u........u..................48
6.3.2 Estimates based on design rainfall bursts with a limit of extrapolation of 1 in 100 AEP m 49
6.3.3 Estimates based on design rainfall bursts with a limit of extrapolation of 1 in 2000 AEP . 50
6.3.4 Estimates based on design rainfall storms with a limit of extrapolation of 1 in 2000 AEP 50
6.3.5 Preliminary estimates based on regional information...muuuuuwu..u....n...mu..mumu....51
6.4 Joint probability analysis of initial reservoir level..n..uuuu..u.uu.............................uu.n........u.uuu.u 51
6.5 Estimation of concurrent flows .unu..u..m..m..uu.u..........u..muuu.wu..u..w.......uu..unwu.....umum 53

References .u..... n u. n. n m.. n............. ...u U" un u... n. n n.... n.. n uu. n.. n... n.......... n. un.... u....... n...u __ u. n ...u u. 55