Environmental Geology of the Marquam Hill Area

• Main Author: Redfern, Roger Alan
• Format: Others
• Published: PDXScholar 1973
• Subjects: Geology > Oregon > Portland; Marquam Hill Area (Portland; Or.); Geology
• Online Access: https://pdxscholar.library.pdx.edu/open_access_etds/2124; https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=3124&context=open_access_etds

This work on Marquam Hill area in Portland, a relatively undeveloped urban hillside area, is a pilot study in which environmental factors are evaluated quantitatively in order to delineate limitations on development. The study was undertaken at the request of and in cooperation with the City of Portland Planning Commission and with the State of Oregon Department of Geology and Mineral Industries. Factors considered include various aspects of the land, vegetation and attitudes of inhabitants. Findings are not intended to satisfy need for individual site studies by qualified experts but should show where that expertise is needed. Field data were collected on site by observations, borings, personal interviews and by geophysical surveys; laboratory tests were made on soil samples; studies were compiled of topographic maps and aerial photographs; and pertinent data from available previous works were incorporated. Data were integrated into a series of environmental factor maps including ground slope, bedrock and soil, bedrock structure, soil thickness, ground stability, hydrology, and vegetation. Land use constraints and environmental limitations were defined using u.s. Department of Agriculture, Soil Conservation Service, soil suitability and limitations criteria as a guide. Mapped geologic and environmental constraints were overlayed with the mapped soil criteria to identify areas by limitations. An interpretive map and chart show that most of the study area is moderately to severly limited for most land uses. Some small areas can be considered as slightly limited, but the majority of these are already developed. The constraints are so severe that most of the area should be left in open space. The major recommendation is that any development must be carefully controlled, utilizing stringent grading codes (such as Chapter 70 of the Uniform Building Code) and professional expertise to assure the safety and environmental compatibility of the site. It is suggested that planned unit development, in the form of clustered or low- to medium-rise structures would optimize design for natural conditions, siting locations, and residential density least affecting the surrounding, naturally vegetated, hazardous slopes.