“the warnings work according to the river ... - hydrology · x. deterministic forecast. analysis....
TRANSCRIPT
“The warnings work according to the river levels whereas actually weought to maybe be giving people warning when we’re expecting excessiverainfall”
David Cameron, 19th November 2010 (BBC Cornwall website)
Structure
The contextKey challengesThe future
Reproduced by permission of Ordnance Survey on behalf of HMSO. © Crown copyright and database right 2010. All rights reserved. Ordnance Survey Licence number 100026380. © Environment Agency.
Bruton 1917
Cannington 1924
Lynmouth 1952
Martinstown 1955
Chew Valley 1968
Chulmleigh 1982Polperro 1993
Boscastle 2004
Ottery St Mary 2008
St Ives 2009
Reproduced by permission of Ordnance Survey on behalf of HMSO. © Crown copyright and database right 2010. All rights reserved. Ordnance Survey Licence number 100026380. © Environment Agency.
Tanhouse Stream, Lostwithiel (Uzella)
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
18:1518:4519:1519
:4520:1
520:4521:1521:4522
:1522:4
523:1
523:4500:1500
:4501:1
501:4
502:1502:4503
:1503:4
504:1
504:4505:1505
:4506:1
506:4
507:1507:4508
:1508:4
509:1
509:4510:1510
:4511:1
511:4
512:1512:4513
:1513:4
514:1
5
Time (16/17th Nov)
Rai
nfal
l (m
m)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Wat
er L
evel
(m)
luxulyan rain Tanhouse Stream
Mevagissey (Fire Station Screen)
0
2
4
6
8
10
12
18:15
18:45
19:15
19:45
20:15
20:45
21:15
21:45
22:15
22:45
23:15
23:45
00:15
00:45
01:15
01:45
02:15
02:45
03:15
03:4504:1
504
:4505:1505:4
506
:1506:4
507:1
507
:4508:1
508
:4509
:1509:4
510
:1510:4511:1
511
:4512:1512:4
5
Time (16/17th Nov)
Rai
nfal
l (m
m)
0
0.5
1
1.5
2
2.5
Wat
er L
evel
(m)
Helligan mg fire stn u/s
Images: bbc website, Adam Gerrard SWNS.com
Key Challenges
Rainfall Rainfall Runoff modelsCoverage
Image: Adam Gerrard SWNS.com
Radar Radar actualsactuals
RaingaugeRaingauge
Observed Forecast
Numerical Weather PredictionNumerical Weather Prediction
Radar based forecastRadar based forecast
Precipitation Hierarchy
Event rainfall totals
0
10
20
30
40
50
60
70
Helligan Luxulyan Bodmin Bastreet St Clether
Location
Rain
(mm
)
0
10
20
30
40
50
60
% D
iffer
ence
Rain gauge Radar Observed Difference
Maximum Hourly intensities
0
5
10
15
20
25
30
35
40
45
Helligan Luxulyan Bodmin Bastreet St Clether
Location
Rain
(mm
/hr)
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
% D
iffer
ence
Rain Guage Radar Observed Difference
6:19 am Predannack 45 degrees azimuth
0
5
10
15
20
25
30
35
40
45
500 50 100 150 200 250 300 350 400
Range (bin)
Rai
n ra
te (m
m/h
)
Uncorrected RCorrected R
River Neet – Woolstone Mill
Woolstone Mill observed radar and TBR cumulative catchmnet rainfall 17-11-2010
0.0
5.0
10.0
15.0
20.0
25.0
00:15
GMT
01:15
GMT
02:15
GMT
03:15
GMT
04:15
GMT
05:15
GMT
06:15
GMT
07:15
GMT
08:15
GMT
09:15
GMT
10:15
GMT
11:15
GMT
12:15
GMT
13:15
GMT
14:15
GMT
15:15
GMT
16:15
GMT
17:15
GMT
18:15
GMT
19:15
GMT
20:15
GMT
21:15
GMT
22:15
GMT
23:15
GMT
Time (hh:mm)
Rai
nfal
l (m
m)
Observed TBRCumulative TotalObserved RadarCumulative Total
River Neet – Woolstone Mill
time Forecast uncertainty
Climatology
Initial Condition Uncertainty
X
Deterministic Forecast
Analysis
Ensembles
Confidence in rainfall runoff models with extreme and localised rainfall
Confidence in rainfall runoff models with extreme and localised rainfall
Confidence in rainfall runoff models with extreme and localised rainfall
Confidence in rainfall runoff models with extreme and localised rainfall
Ottery St Mary 2008
0.0
0.5
1.0
1.5
2.0
2.5
16/11
/2010
21:00
16/11
/2010
23:00
17/11
/2010
01:00
17/11
/2010
03:00
17/11
/2010
05:00
17/11
/2010
07:00
17/11
/2010
09:00
17/11
/2010
11:00
17/11
/2010
13:00
17/11
/2010
15:00
17/11
/2010
17:00
17/11
/2010
19:00
17/11
/2010
21:00
17/11
/2010
23:00
18/11
/2010
01:00
18/11
/2010
03:00
18/11
/2010
05:00
18/11
/2010
07:00
18/11
/2010
09:00
Stag
e (m
)
Observed Stage
Simulated stage usingthe old ratingSimulated stage usingthe new rating
Image: BBC website
Summary
Errors in deterministic rainfall forecastTargeting probabilistic rainfall forecastsRain gauge densityAssumptions of modelling approachesCoverage of good quality hydrometric dataCulverts and trash screens
The Future…
Image: AP
