The city's jail system is in deep trouble, said Joseph Ponte, the city's new Department of Correction Commissioner, during a city council hearing Monday.

The situation at Rikers Island is dire, he said, pointing to sharp spikes in violence. The use of force by guards increased 59 percent between 2010 and 2013. During this same period, stabbings and slashings doubled, and assaults on staff increased to 646 from 500.

Ponte testified that overwhelmed staff were using outdated methods to try to control a group of difficult inmates that included the seriously mentally ill and troubled adolescents.

"They operate an aging, inefficient physical plant, face limitations on information that should inform custody management choices, and have a training program that has yet to catch up with the reality of a growing concentration of inmates who are legitimately hard to manage," Ponte told councilmembers.

The correction official said guards often don't know why an inmate was arrested. The information, he said, could help prepare them for what behaviors they should expect. 

The testimony came as Mayor Bill de Blasio announced the formation of a task force to find ways to divert the mentally ill away from jail by intervening earlier and providing more comprehensive mental health services. The task force will also examine how the system can ensure that mentally ill inmates get the  health services they need after they are released, so that they are less likely to return to jail. Ponte estimated that 40 percent of the Rikers population is mentally ill, up from 24 percent in 2007.

The task force will have 100 days to develop recommendations and begin implementing them.