Chief Superintendent Stephen Cargin said there had been a fourfold increase in the number of shootings so far this year compared to all of 2013.
In all this year, 25 paramilitary-style incidents have occurred.
As well as the 13 shootings there have been pipe bomb incidents, assaults and criminal damage in the Foyle, Limavady, Magherafelt and Strabane areas.
C/Supt Cargin said that of the 13 shootings, 11 were attributable to dissident republicans
He said: “These figures are very concerning and tackling these issues is one of my priorities.
“Last night, the life of a young man from this city was put at risk and his future probably changed for ever by the barbaric actions of a few thugs
“At around 11pm, the 17-year-old was shot in the left thigh and right calf in a green area in Ballymagroarty by two men.
“His father then had the task of driving his injured son to hospital. He is receiving the best possible medial treatment, and while his life is not thought to be in danger, there may be longer term consequences.
“The victims have been the subject of brutality meted out by some who claim it is some kind of justice.
“This is not justice. Justice means that people should be able to account for their actions and openly defend themselves. Justice means that outcomes should be appropriate, and not handed out at the point of a gun by people who dare not show their faces.
“Once again we are going back in time. Many people believed we had moved on, and we have. Derry is a city that is unrecognisable to what it was 10 or 20 years ago. It is a city of hope and a beacon not just in Northern Ireland, but internationally.
“In pure financial terms, the costs added to policing by these actions has been £570,000 over the past five months.
“We have put additional resources into patrols in the city, and while we can never quantify these tings, we believe we have thwarted attacks.
“We have also made 19 arrests since February in relation to these incidents and terrorism generally. Two people have been charged.
“Shootings like last nights are designed to terrorise and bring fear to communities.
“Those who carry out these attacks are to be condemned, and they are to be brought before the courts.
“To do that police need information. Our appeal is for people to tell us what they know about this attack, and any others – or about the faceless people who carry them out
“The irony is that when we catch the people who carry out such brutal attacks, they will be treated with the proper justice and mercy that they deny their victims.