Last week, amid torrential rainfall and flash flooding in Houston, Andrew Calder took a call from an attorney at his law firm, Kirkland & Ellis LLP.The attorney and a staff member commandeered a kayak and wanted to know which areas in the city would benefit from rescue efforts.“We had associates, members of staff and partners all over the city volunteering at shelters and actually taking boats out onto the water trying to help people out of their homes, which was awesome,” said Calder, a partner at the firm …