Annual and monthly rainfall data for Kano from the period 1911 to
2010 (100 years) were used in this study to determine the changing patterns
of rainfall and its adverse impacts on transport infrastructures. The Relative
Seasonality Index of the rainfall series revealed that the rainfall is in 3
months or less. In order to identify trends, the rainfall series was divided into
10-year non-overlapping and 30-year overlapping sub-periods and the
Cramer’s test was then used to compare the means of the sub-periods with
the mean of the whole record period. The results of the 10-year nonoverlapping
sub-period analysis revealed a recent increase in the annual
rainfall series in the last two sub-periods (1991-2000 and 2001-2010). The
results of the 30-year overlapping sub-periods analysis also revealed that the
recent sub-period, 1981-2010, was significantly wetter than the long-term
conditions. Findings revealed that the increase in annual rainfall amount in
recent years is as a result of the increased in June, July and August rainfalls.
This may be responsible for the frequent occurrences of floods in the months
of July and August which is an indication of climate change. The 10-year
running mean shows that the increasing yield of the annual rainfall started
from the mid 1990s to the end of the study period. The major implication of
this increased in amount and intensity of rainfall on transport infrastructures
is that models built on the perceived decreasing rainfall, such as drainages,
bridges, etc, have to be reviewed. It is recommended that planning and
designing of transport infrastructures should take into account the recent
increasing nature of rainfall.