It was a city of more than 100,000 people in a desert. Think about it: do you honestly believe a city that size could have, or would have, evacuated completely? Where would they all have gone? Where could they get food and water?
Many of them were simply trapped by circumstances.
The US was going out of its way to do surgical strikes.
A few civilians may have been killed. But to claim that 3/4 of the ones we killed were civilians, is preposterous, unless you count terrorists as civilians, of course.
They'd get their food and water from the same place they've been getting it all along while under seige- Baghdad. Not to mention the US and aid organizations have been outside the city ready to provide water and other essentials for those who chose to leave all along. (It's part of the reason supporters were able to resupply the insurgents, unfortunately.)