AN ECONOMIST has claimed the Sekisui House development is vital to accommodating the Coast's growing number of tourists, spurred on largely by the Marcoola airport expansion.

Interested members of the public overflowed from the gallery into jury seating on day three of a Planning and Environment Court hearing in Maroochydore as Sydney-based economist Gavin Duane explained the Sunshine Coast's overnight and international visitors were forecast to double over 20 years at a rate of 4 per cent a year.

The hearing - which is expected to run for three weeks - will determine whether the Sekisui development will go ahead.

Community groups Development Watch and Sunshine Coast Environment Council brought on the legal proceedings action against the Sunshine Coast Council and Sekisui Development.

Mr Duane attributed the projected tourism growth largely to the Sunshine Coast Airport Expansion Project, which he said would attract more visitors who sought diverse, nearby accommodation for leisure, business, entertainment and conference purposes.

Experts will be called to give evidence on 21 "key matters" including visual amenity, turtles, town planning, architecture, lighting with respect to turtles, photo montage preparation and traffic.

Mr Duane co-authored a report which explored Sekisui relative to the Sunshine Coast airport, tourism and visitor growth, housing size, projected population growth, residential supply and demand, employment and existing infrastructure.

In June 2018, Sunshine Coast Council approved Japanese developer Sekisui's 220-room Westin hotel, with the broader resort comprising 148 serviced apartments, 753 residential apartments, 98 two to three-storey homes and a 2770sq m retail village.

Mr Duane said the Sekisui site was identified as a "tourism area" in the planning scheme, and the development "distinguished itself" from existing five-star approvals, such as the Aria in Mooloolaba and Badderam in Buderim given its proximity to the airport, its "beachfront" location and the area's proven tourism appeal during the Palmer Coolum Resort's heyday.

He said it was economically beneficial to "take advantage of existing infrastructure", such as the Palmer resort's golf course, and suggested it reopen in conjunction with Sekisui House.

Sekisui's four-storey units and its townhouses would address the "missing middle" of residential medium-density accommodation, currently not available in numbers on the Sunshine Coast, according to Mr Duane.

Based on 2016 figures, the economic report forecast a shortfall

in residential housing supply in the subject area over the next 12 years to 2031, but Mr Duane acknowledged the projections did not include dwellings constructed between 2016 and 2019.

Mr Duane said Sekisui House had the potential to become one of the most significant employers in the Coolum area, coupled with Twin Waters 362-room Novotel Resort and surrounding major retail complexes. He said he could not comment on Development Watch barrister Philip Hack's claim Sekisui would create traffic congestion.

The hearing continues in Maroochydore tomorrow.