1918.] 
The N.Z. Journal of Science and Technology. 
293 
PHENOMENAL RAINFALL AND FLOODS IN THE 
NORTH AUCKLAND DISTRICT. 
By J. Wood, Assoc.M.Inst.C.E., Resident Engineer, Public Works 
Department, Whangarei. 
On the 2nd and 3rd February, 1917, the district north of Auckland 
•experienced phenomenal rainfalls and was visited by floods much higher 
than any previously recorded. The district that suffered most lies between 
the Wairoa River and the Hokianga River, towards the west coast, and 
it was in this locality that records were taken of the flow of the rivers in 
flood. The results obtained are remarkable, the run-offs from the drainage 
.areas being higher than any records that have, as far as the author knows, 
•ever been recorded in any country. 
A plan showing the rivers that were gauged for flood-discharge, and 
also the sites of the rainfall-gauges given in Table I, was published in a 
previous paper, entitled “ Floods in North Auckland District,”* to which 
the reader is referred for other aspects of the subject. 
Table I.—Daily Rainfall, in Inches, from the 26th January to the 6th 
February, 1917. 
■ Station. 
Jan. 20. 
Jan. 27. 
Jan. 28. 
Jan. 29. 
Jan. 30. 
1 
Jan. 31. 
Feb. 1. 
oi 
rO 
<D 
Feb. 3. 
Feb. 4. 
Feb. 5. 
Feb. 0. 
Total. 
Umawera 
0-13 
0-30 
0=10 
0=63 
' 
0=30 
1=20 
9=10 
0=12 
11=88 
Rangiahua . . 
0-20 
0-09 
0-17 
0-07 
1-09 
0=29 
0-54 
4=87 
4-06 
0-34 
• e 
11=72 
Kohukohu . . 
, . 
• • 
• • 
0=06 
0=57 
0=05 
0=10 
0=75 
3=60 
4=68 
0-31 
0=03 
10=15 
"Taheke 
0-08 
0-41 
1-07 
0=78 
0-31 
0=72 
0=78 
9=09 
1=75 
0=51 
0-35 
0=10 
15=95 
Wekaweka . . 
0-30 
0-25 
0-46 
0=07 
1=56 
0=72 
0=53 
5=20 
3=44 
0-22 
0-72 
0=03 
13=50 
Keretoki 
0-20 
019 
0*25 
0=05 
1=70 
0-35 
0=35 
5=50 
4=57 
0-24 
13=40 
Waimatenui . . 
• • 
0-20 
0-14 
0=02 
1=62 
0=61 
0-63 
5=65 
4=14 
0-05 
0=37 
0-03 
13=46 
Pakotai 
• • 
0-51 
0-54 
0-87 
0=18 
1=69 
1=75 
1-07 
4-83 
4=15 
0=55 
0=29 
16=43 
Wairua Falls 
0-21 
0-05 
0-04 
0=21 
0=36 
0-17 
0=12 
3=09 
3=27 
0=05 
0=18 
0=02 
7=77 
Mangarata . . 
. . 
o . 
0=15 
0-21 
. . 
0-85 
0-26 
2=43 
3-89 
0=26 
. . 
8=05 
Whangarei . . 
0-28 
0-32 
0-33 
0-05 
0=75 
1-23 
0=47 
2-37 
1=76 
0=09 
7=65 
Table I gives some idea of the phenomenal character of the rainfall 
•on the 2nd and 3rd February. At no fewer than six rain-gauge stations 
over 8 in. was recorded for these two days, at three of them over 10 in. of 
rain fell, while at two of these stations 9 in. was recorded for one day’s 
rainfall. Another thing to be noticed is the quantity of rain that fell 
■during the seven days prior to the downpours on the 2nd and 3rd. The 
•effect of this would be to cause a complete saturation of the. ground, which 
would contribute largely to the high rate of run-offs recorded below on the 
days of the extraordinary rainfall. 
In Table II are shown several rivers which were investigated by the 
author to find out the quantity of water that was being discharged by the 
floods during this heavy rainfall. 
*Proc. N.Z. Soc. Civ. Eng., vol. 4, pp. 77-123, 1918. 
