It has been my fate for most of my life to live in towns where rivers are deeply important to the local community. Given that rivers are a ready source of water, and also are major arteries for trade, it is little surprise that so many of the places where I have lived, from Pittsburgh to Tampa to Chaing Mai to Portland, have been greatly defined by the importance of the rivers as a means of providing those cities with powerful regional importance as cities in the nexus of at least national trade, if not global trade. In none of these cases did the river serve as any sort of boundary at all—rather in all of these cities, the river (or rivers) that flowed near and through the cities provided the life-giving water to feed its population and provide it with potable drinking water, provided the dangers of floods, and also provided the areas with opportunities for riverine trade and communication. In addition to this, and of particular personal interest as an engineer by education, is the fact that these cities are known for striking bridges  that seek to connect the people from part of the metropolitan area with those on the other side of the river. The importance of bridges, and their immense worth in demonstrating that rivers need not separate people, but can provide means of common interest and community, is a lesson that we are perhaps not quick enough to learn in our day and age.
The fact that I view rivers as primarily trade and communication routes, places for pleasing mutual intercourse and common interest and community efforts is perhaps strikingly at odd with the general zeitgeist. More emblematic of our day and age is the way in which people wish to use at least one river in particular, the Rio Grande, as the location for a wall to separate ourselves from the problems of our troubled southern neighbor Mexico, and from the hordes of people yearning to enter the United States. Let us pass as charitably as possible over the hypocrisy by which Mexico treats its own migrant population with immense harshness while seeking the most favorable treatment of its own unwanted immigrant population here, and let us pass over as charitably as possible the hypocrisy of a nation founded entirely by immigrants showing a hostility to other immigrants—for there are no truly ‘native’ people on this continent whatsoever, all people are descended from immigrants of some kind, some from thousands of years ago, some from hundreds of years ago, and some much more recent. These are differences only in scale and in chronology, not in kind. The fact that it is a river that forms a long stretch of our border with Mexico makes it a particularly poignant reminder of what happens when neighbors do not wish to act neighborly on either side, for rivers exist for only a few purposes, and a wall is not one of them. Either rivers are meant to provide opportunities for the flow of water, food, communication, and the transportation of various people and products, or they provide opportunities for bridges and fords to join the people on both sides who would otherwise be separated by those same life-giving waters.
Why would someone build a wall when they can build a bridge? The purpose of a wall is to protect and defend, and is done because one views oneself to be in a dangerous position. It is designed to prevent harm and loss, but serves no other positive benefits. Its costs are to be charged against what one would otherwise lose, and its opportunity costs are based on the losses that one gains from shutting off those who are not enemies at all who are kept outside of the walls as if they were. For a bridge, the matter is reversed. Bridges certainly serve aesthetic purposes, whether one is talking about the geometrical beauty of a triangular truss bridge, or the soaring elegant span of a suspension bridge, or the beauty of a draw bridge, so long as one is not stuck waiting while it is open to let a boat through. Certainly they are at least equal to the aesthetic achievements of a castle or the Great Wall of China or other fortifications. To this aesthetic beauty is attached immensely practical benefits. While a wall can only keep people out, or trap people inside, a bridge allows people to go from one place to another, providing ease of transportation of people and goods, allowing networks of people to build up in a given river valley that would otherwise be divided by the waters that draw those on both sides. For a bridge, its cost must be drawn against the benefits of the trade and transportation that the bridge brings about, by the growing area that is connected together, and its benefits based on expansion and flow. Even a bridge built in the middle of nowhere, like the High Bridge of Virginia or a bridge in Alaska, is at least a sign of hope that people will be drawn across the waters from a place to the other side of the river.
So, when I sit at a river, whether it is in Western Pennsylvania, where I first drew breath, or along the lazy swamps of Central Florida, where the Hillsborough River snakes its way through the city of Tampa, or even the Willamette and Columbia Rivers of the Portland area where I now reside, when I look to the other side of the river, I see a place that I want to be connected with. I do not see on the other side of the river people who are entirely alien and hostile to me, people who need to be walled off and prevented from any kind of access to the world I enjoy and appreciate, but rather I see people who can be connected to me and to my influence, for mutually beneficial and enjoyable intercourse in trade and communication. I do not know what others see when they look at the same rivers. Do they see the traffic of boats with and against the current, look forward to the potential of hooking some kind of fish (if they are so inclined), or appreciate the fact that rivers offer inexpensive options for transportation by boat, as well as convenient places to put ports and bustling cities? Or do they look with fear over those on the other side of the river, paralyzed with fear at the harm that they think is likely to come from them should they find their way across? Our lives are too short, and too filled with difficulty and trouble as it is, for us to be continually tormented by fear as we huddle behind our walls because we lacked the courage and faith to build a bridge to the other side of the river, where we may find people not unlike ourselves, if we only had the courage to try.
 See, for example: