This is a picture of the areas in Singapore that has been flooded[Google Map Link] courtesy of Kojakbt:
You can superimpose that on to the canal system [Link].
I urge you not to jump into various conclusions how ever logical and obvious as they may seem because we are not experts and cannot prove anything rigorously without more data - there are also other plausible explanations e.g. underground works and construction have affected the flow of underground water. The authorities have created many convenient explanations that seems to put blame away from themselves ..and changed them along the way when the older explanations cannot fit the new observations - once in 50 years rainfall, debris in drain, etc. That is not the way to win confidence and reassure the public. There are people who have suffered serious damage to property and business who deserve better answers.