Former Sandgrounder, 29-year-old Dugdale, first played for Southport on loan from Crewe Alexandra in 2007, making eight appearances.
He joined the club permanently the following summer, playing in a further two league games.
He then spent time at Droylsden, Barrow AFC and AFC Telford United before re-joining Crewe.
In five years, Dugdale (pictured) made 120 League appearances at Crewe and was part of the team that won the League Two play-off final at Wembley Stadium in 2012.
Since leaving Crewe in 2015, he has played at Tranmere Rovers, Morecambe and Eastleigh.
Port boss Alan Lewer told southportfc.net: “We’ve been pursuing Adam for a while. He wanted to move back up north and we’re very happy to have him.
“We want to get the spine of the team right, and we’ve got Adam at the back, Steve Jennings in the middle and Jack Sampson up top. We’ll be adding to that over the next few weeks but we’re very happy with where we are so far”
Dugdale said: “I’m really made up to be back at Southport. I was at Eastleigh last season but it was a long way away from my family. I wanted to come back up north and start enjoying my football again.
“We’re going to go about our business quietly but we know we can get the club back up to the National League where it belongs.”
Guinea-born Kpohomouh, 20, began his career at Irlam FC, winning promotion to the Hallmark Security League Premier Division and winning the league’s player of the season award.
He had a brief spell with Welsh Premier side Bangor City before joining Evo-Stik League North outfit Radcliffe Borough.
Lewer added: “I watched Jacques on trial at Crewe about 14 months ago. He’s a great man marker. His aim is to get into the first team. He’s got a lot to learn but that will be down to him over the next three or four months. Working with Mark Wright day in day out will help him tremendously. He’s got a fantastic leap and he’s got a lot of potential.”
Kpohomouh said: “I knew Alan at Bangor, I knew I wanted to work with him again at Southport when he became manager. I just want to work hard, make sure I’m in the first-team and get as many clean sheets as possible”.