HR: 0800h
AN: H41D-0452    [Abstracts]
TI: Hydrological and Hysteresis Response of Open Lined Channels in Small Urban Residential Catchments in Singapore
AU: * Lee, W
EM: g0305733@nus.edu.sg
AF: National University of Singapore, NUS, 1 Arts Link Singapore 117570, Singapore, 117570 Singapore
AB: Two small urban residential catchments, namely Jurong West (JW) (1 ha) and Ang Mo Kio (AMK) (0.6 ha) in Singapore have been selected as sites to investigate hysteresis patterns and hydrological responses from catchments' pervious surfaces and different types of impervious, namely directly connected impervious areas (DCIA) and non-directly connected impervious areas (Non-DCIA)during rain events. Results from February 2005 till May 2005 have been analyzed. Table 1 \begin{tabular}{|1| |1| |1| |1| |1| |1|} \hline {c}{JW}
\cline{1-6} Date (d/m/y)&Rainfall(mm)&(Time Lag)(mins)&(Time Of Rise)(mins)& Antecedent Dry Days&Previous Rainfall event (mm)
\hline 26/02/05&13.6&20&5&1&0.8
03/03/05&1.2&23&15&0&28.4
10/03/05&7&18&15&1&7.4
12/03/05&4.6&22&10&1&7.4
26/03/05&15.2&14&15&0&6.8
02/04/05&2.2&12&15&1&3.8
21/04/05&3.8&19&10&3&0.4
28/04/05&28.6&8&23&6&3.8
04/05/05&1.6&19&14&0&7.8
12/05/05&14.2&12&15&1&20.6
\hline {c}{AMK}
\cline{1-6} 11/03/05&12&15&10 3&0.2
23/03/05&21.4&10&10&11&12
26/03/05&10&32&32 2&21.4
31/03/05&7.8&13&19&0&2.8
02/04/05&10.6&9&9&0&1
12/04/05&15.8&12&10&0&10
24/04/05&8&8&4&5&4.6
\hline \end{tabular} From the selected rain events (Table 1), duration for direct runoff from impervious surfaces for JW and AMK catchments ranges from 10 - 15 minutes and 4- 10 minutes respectively. Antecedent dry period did not play a critical role in influencing time-lag for both catchments. Although rise in magnitude of rain event does not proportionally lead to decrease in lag time, it is more influential as compared to antecedent dry period factor. Majority of time of rise for each rain event is 10 - 15 minutes and 4- 10 minutes for JW and AMK respectively. This indicates a direct runoff from constant degree of impervious surfaces. The influence of the magnitude of rain event rather than impervious surfaces was also shown in multi-rain events (Table 2). It has been shown that in most cases, a lower magnitude of consecutive rain event will increase lag time of preceding rain event. Table 2 \begin{tabular}{|1| |1| |1| |1|} \hline {c}{JW}
\cline{1-4} Date (d/m/y)&Rainfall(mm)&(TL)(mins)&(TOR) (mins)
\hline 26/02/05&13.6&20&5
&44.2&4&10
\hline 03/03/05&1.2&23&15
&1.2&45&30
\hline 12/03/05&4.6&22&10
&6&15&10
\hline 02/04/05&2.2&12&15
&0.8&64&40
\hline 12/05/05&14.2&12&15
&4.8&15&10
&11.2&19&45
&3&18&65
\hline {c}{AMK}
\hline 26/03/05&10&32&32
&38.4&6&15
\hline 31/03/05&7.8&12&19
&12.8&9&20
\hline 02/04/05&10.6&9&9
&3&14&14
&2&12&20
&1.2&22&15
\hline 24/04/05&8&8&4
&2.6&11&5
\hline \end{tabular} Table 3 \begin{tabular}{|1| |1| |1|} \hline {c}{JW}
\cline{1-3} Clockwise (mm)&Anti-clockwise(mm)&Eight-Shaped (mm)
18/02/05(7.6)&27/03/05(4.4)&02/03/05(11.6)(1315-1530hrs)
28/02/05(5.2)& &06/03/05)(1.6)
02/03/05(16.6)(0530-0730hrs)& &15/03/02(1.6)
03/03/05(2.6)& &06/05/05(34.8)
03/05/05(7.5)
24/03/05(46.6)
06/04/05(15.8)
28/04/05(28.6)
\hline {c}{AMK} \cline{1-3} 11/04/05(10)& &24/04/05(10.6 )
12/04/05(15.8)
\hline \end{tabular} Results showed clockwise hysteresis patterns are common (Table 3). This could be explained by residential carparks upgrading works near gauging stations. Other possible sources include sediment from DCIA impervious surfaces.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1825 Geomorphology: fluvial (1625)
DE: 1850 Overland flow
DE: 1874 Ungaged basins
SC: Hydrology [H]
MN: Fall Meeting 2005