INTRODUCTION
Vedder Crossing
In order to provide effective information to help minimize flood damage in British Columbia, floodplain mapping is critical for the federal and BC governments. However, BC communities that lack up-to-date floodplain maps risk billions of dollars in property damage and even the lives of their citizens when disaster strikes (Vancouver Sun, 2015). For instance, Two major river systems flow through the City of Chilliwack, the Vedder (a.k.a. Chilliwack) River and the Fraser River, and figures above indicates the area of Chilliwack River at Vedder crossing as subject to recurrent and severe flooding. However, due to the tendency of climate changes, temperature and precipitation extremes have grown dramatically in recent years, leading to an increase in flood risks in the watershed (OECD iLibrary, 2010). In this case, compared with old flood risk areas, there should be more potential flood risk areas which are not determined currently in the watershed. Water levels rise on the Vedder River during the spring and summer as a result of snowmelt, but the larger floods on the Vedder River occur in the fall and winter, brought on by heavy rainfall or rain-on-snow events (City of Chilliwack, 2011). Therefore, mapping an updated floodplain map is a significant task for these areas with the issues mentioned above.
Floodplain Mapping of Chilliwack River at Vedder Crossing (Ministry of Environment INVENTORY and ENGINEERING BRUCH, 1987)
The purpose of this project is to develop a floodplain map to assist the Fraser River Flood Protection (2008) and the Vedder River Flood Protection (2011) plans for the Chilliwack River Watershed, solving the potential risks due to data missing or out-of-date data. By utilizing GIS applications, remapping the floodplain of the watershed to identify areas where high flood risks exist and, to estimate the spatial distribution of flood water. Based on the new floodplain map, the policy makers or managers can implement better management of infrastructures such as storm water systems, roads and bridges, flood protection works, and reservoirs, which can help to avoid the high impact of a large-scale disaster. This project will provide useful information make a positive contribution to landowners, governments, local communities, and even insurance companies who pay large sums in for flood insurance claims every year (Insurance Information Institute, 2015).
Study Area
The study area selected for this project is Vedder River as one of the major river systems in City of Chilliwack, BC. Tha map above shows the area of Chilliwack which is located approximately 100 kilometres east of the Vancouver, and Figure 4 above shows the location of Vedder River and Slesse Creek. This project aims to update the map of the floodplain of that location (Above Vedder River Crossing to Slesse Creek Tributary) to review risk areas.
Objectives:
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Apply GIS and simulation software to develop updated floodplain maps under two flood return periods for the study area.
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Determine flood frequency return period based on historical flood data, and estimate impacts caused by climate changes on future probabilities of flooding.
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Identify and analyze areas should be reconsidered as risk areas compared with historical floodplain map.