Civil engineer here - had a similar situation in undergrad, with an electrical engineering prof trying several times to get me to switch based on my interests. There are a lot of opportunities to do coding and tech stuff in civil engineering, and I think working on big infrastructure projects is way more exciting than building a startup or the next great phone app. You should consider grad school, or at least take some grad level courses your senior year, if you want to learn to code and solve civil engineering problems. It isn't necessary, but grad school will give you classwork where you need to learn to code to solve them, and you'll have no problem finding a job if you can show programming and data analysis skills on your resume.
I currently work in water resources, maintaining a Monte Carlo models of systems of dams that is used to estimate changes to flood risk and other impacts - both as a result of climate change and changing regulations. The job feels a lot more like software engineering or tech support some days, so there seems to be a lot to learn from HN.
If you are looking to learn to code while doing civil engineering, or at least water resources, Python, R, Matlab, and even VBA for Excel are all commonly used. Focus on getting really good with one of them. A lot of the software I deal with is written in a combination of Java for the UI and FORTRAN for the computational engine, so having some background in those doesn't hurt, but definitely secondary.
(As for the original Ask HN post - I started reading HN a number of years ago after some more tech-oriented friends kept sending me links to discussions here - mostly stick around for vintage Mac shenanigans and stories, and the comments on them, but also often take a look at posts with career and leadership advice.)