HONG KONG — Smoking a cigarette outside a mall in the border town of Sheung Shui, a man who gave his name only as Chen stands next to a wheeled cart filled with purchases. He is visiting from the Chinese city of Shantou, 177 miles away, a trip he makes several times a year.

“When I come to Hong Kong, it’s mainly to buy medicine — maybe some food products, too,” said Mr. Chen, who declined to provide his full name because of a crackdown on illegal exporting. “There are more brands available here, many of which you can’t find back home. On the mainland, there is also a lot of counterfeiting.”

Shoppers like Mr. Chen are the new face of Chinese spending in northern Hong Kong, and their vast numbers are changing the landscape near the former British colony’s border with the mainland. Retail space in these areas, collectively called the New Territories, and along the rail line running through them, is increasingly oriented toward mainland day-trippers and “parallel traders” from Guangdong, the southern Chinese province, who buy items for resale at a markup in China and avoid import taxes.

According to mainland customs data, more than 20,000 parallel traders cross the border daily, not including thousands of individuals doing personal shopping. Added to an acute housing shortage, this has led to more than $15 billion worth of planned construction, including millions of square feet of shopping and thousands of new apartments. But even as business booms, the influx pushes up retail rents and forces businesses aimed at local residents to move or close.