Sustainable Urban Community Development: A case study of flood design in Snoqualmie, WA, USA

Thesis (Master's)--University of Washington, 2014University of Washington Abstract Sustainable Urban Community Development: A case study of flood design in Snoqualmie, WA, USA Pin-Hao, Huang Chair of the Supervisory Committee: Associate Professor, Daniel B. Abramson Department of Urban Design and Planning Flooding is an important issue in Snoqualmie. Floods occur almost every five years. They are caused by multiple factors: massive precipitation in winter, melting snow in spring, and Snoqualmie River's convergence upstream of Snoqualmie city. Flood management in Snoqualmie is complicated because of two main reasons: historic buildings in downtown area and the National Flood Insurance Program (NFIP). For example, since the National Flood Insurance Program requires house owners who own houses in the 100-year flood zone to pay high insurance fees, they reduce house owners' budgets to elevate endangered houses. This thesis explores effective ways to manage flooding impact from an urban design perspective. It tries to consider what viewpoints engineers lack, such as design aesthetic and integrity. Through comprehensive analysis and diverse flood management research, this thesis proposes flood-proofing designs and strategies for Snoqualmie. Flood-proofing is of particular interest because we live in a flood-threatened world. Urban areas are often more susceptible to the damage caused by flooding due to high population densities and inadequate infrastructure design. Climate change in recent history has also significantly changed precipitation patterns and increased the chance of flooding in many regions. This thesis intends to find suitable flood-proofing designs and strategies for Snoqualmie, which can be applied to other places around the world. Past studies focus on climate change and the effect of human development on flooding issues. They propose that a good flood management strategy is to live with floods and be resilient to damages (e.g. wet flood-proofing, dry flood-proofing, and house-elevating). Natural systems, such as vegetation, soils, floodplains, and wetlands are better ways to maintain water balance and mitigate flooding. Urban development should be sustainable and less harmful to natural systems. This thesis proposes sustainable and flood-resilient development methods. Two main methods are presented: restoring floodplain habitats by removing structures/setback levees, and constructing detention pounds/bio-swales. Both methods combine open spaces with flood management infrastructure designs. In the historic downtown area, both wet flood-proofing and dry flood-proofing methods are applicable. Box barriers or sandbags are applicable around the area. Buildings can use flood-proofing materials to withstand floods and facilitate easy clean up. Buildings can also use backflow devices on sewer drains. This thesis proposes comprehensive flood management design after analyzing historic maps, zoning maps, flood hazard data, and hydrological data. The research presented here makes substantial use of Geographic Information Systems (GIS) to analyze sites' current conditions, such as development patterns maps and zonings maps. It also forecasts future potential development areas by considering the surrounding ecosystem