Evan C. Thomas

Understanding the physical processes of pollutant build-up and wash-off on roof surfaces.

Pollutants originating with roof runoff can have a significant impact on urban stormwater quality. This signifies the importance of understanding pollutant processes on roof surfaces. Additionally, knowledge of pollutant processes on roof surfaces is important as roofs are used as the primary catchment surface for domestic rainwater harvesting. In recent years, rainwater harvesting has become one of the primary sustainable water management techniques to counteract the growing demand for potable water. This paper presents the outcomes of an in-depth research study into particulate matter build-up and wash-off for roof surfaces. In this research, particulate matter was considered as the indicator pollutant where the processes related to other pollutants can be predicted based on the understanding generated for particulate matter. The study outcomes confirm that the build-up process on roof surfaces is comparatively similar to road surfaces. However, particle loads collected from roofs were significantly less compared to road surfaces and much finer in texture. Wash-off from roofs also showed significant similarities to wash-off from roads. A relatively high concentration of particulate matter was noted during the initial part of storm events. Furthermore, the amount of particulate matter remaining on the roof surfaces was significantly high for less intense rain events.

Translating a risk-based land-use planning issue to a decision making tool using simple GIS approaches

This paper presents the use of simple GIS approaches to translate a detailed risk-based decision framework for on-site-sewage-treatment-facility siting, design and management into the development assessment process. In 2001 the Gold Coast City Council and Queensland University of Technology collaborated in the development of a detailed risk-based approach to the siting-design and management of on-site sewage treatment systems (Septic and aerobic home sewage treatment systems). Within the Gold Coast City area, some 16,000 properties rely on on-site sewage treatment. Studies indicated that about 9,000 of these are septic tanks and that a high proportion of these do not operate to the required standard due to a combination of design, siting and maintenance failures. These data and the increasing recognition of the ecosystem services provided by the Gold Coast hinterland and waterways indicated the need for greater rigour in assessment and management on–site sewage treatment systems. To do this, a risk-based approach was developed that required translation into the development assessment framework. The GIS (MAPINFO - mapbasic) tool developed interrogates a series of existing maintained layers to derive on-site risk-levels for a given parcel of land based on the science from the studies. This tool connects with planning documents and codes that delineate the level of information needed from the applicant to address the identified risks. The tool provides a quick indication of the risks for the assessment officer, allowing information requests to be produced consistently. It is designed to work with layers that the Council has agreed to maintain rather than maps derived during the study. Among the relevant maintained layers are the waterways, geology, soils and slope. In addition, the tool connects with other layers that can assist with the interpretation, such as existing soil data from nearby sites. This approach leads to consistent and science-based approach to development assessment.