By Nicolas R. Malloy October 19, 2025

Introduction

As our climate continues to change, one of the biggest challenges for coastal communities is rising sea levels. Even a small increase in ocean height can cause flooding in low-lying areas, damage infrastructure, and threaten ecosystems. Humboldt Bay, located on the Northern California coast, is especially vulnerable because so much of its surrounding land sits only a few meters above sea level.

In this activity, you will use GIS to explore what sea level rise could mean for Humboldt Bay. By working with a digital elevation model (DEM), you will build a simple model of where water might reach if sea level rose by 1, 2, 5, or 10 meters. The analysis is intentionally simplified. It does not include tides, storm surge, or tsunamis, but it will help you see how sea level rise can be mapped and visualized using GIS tools.

Learning Outcomes

During this activity, you will create maps that highlight the areas most at risk and summarize which types of land use such as residential, agricultural, or recreational would be affected. Along the way, you will practice important GIS skills like managing data, using raster tools, and designing clear map layouts.

By the end of this activity, you will be able to:

• Verify and harmonize dataset spatial references for analysis.
• Prepare rasters for study-area analysis using appropriate extraction tools.
• Model sea level rise scenarios with raster map algebra.
• Classify and encode land use so it can be used in raster-based analysis.
• Convert vector data to raster and align resolution with other layers.
• Perform raster overlay to identify land use categories affected by inundation.
• Quantify impacted area from raster attribute tables and report results clearly.
• Reclassify elevation into interpretable flood risk categories.
• Apply effective cartographic design for quantitative data, including hillshade support and coherent color schemes.

Setting Up Your Workspace

Before beginning the analysis, it is important to create a dedicated workspace for this project. A clear and consistent folder structure will help you stay organized as you move from data preparation to analysis and map design.

Start by creating a new folder on your desktop and name it SeaLevelRise. Inside this main folder, make three subfolders:

• original – for storing the unaltered copies of your downloaded data.