Okay, so, first problem with both maps is that the Raven Rock Mountain Complex is not included in either. Being the US government's hiding hole in the advent of exactly the kind of apocalypse that is described, it would probably be the effective administrative capitol even if Washington DC was reclaimed and reinhabited. I buy that DC would be used as a symbolic capital for legitimacy's sake, but in a world where zombies are still a threat, and especially one where that threat seems to be increasing again, whatever was left in DC would probably get packed up and lugged back to Raven Rock, just in case.
With that out of the way-
What people are missing is the idea of a 'buffer.' If the surviving government, rather than annexing right up to the waterfront, set up a de-facto military government for the regions around DC in order to catch and pick apart the kinds of hordes that practically took down civilization, they'd be significantly more secure in their control of the District of Colombia itself. Of course, the welcome side effect is that in this period of massive instability, the capital would be significantly better protected if a popular uprising or rebellious state decided to move on them. 454
As for farmland, I find it realistic for the soldiers to grow crops, given it has happened historically and being exposed in an open field is now a much more dangerous thing without a weapon and training.
It's defiantly a neo-feudal thing, which might not be what you're going for, but without the kind of manpower, established economic force, and broad-scale public safety against what are effectively wildlife attacks, a decentralized defense-in-depth makes a lot more sense than sending out the airplanes and tanks as a single unified army to annihilate the threats one at a time.
With zombies in particular, small, local and largely self-sufficient fortified garrisons protecting an urban center with the kind of immigration pull a resecured DC would have makes even more sense. Even when Americans in DC lacked voting rights, it still attracted a massive urban population, as any capital tends to.
With few exceptions, they will be fighting smaller, more numerous hordes, only coming together when the government detects a particularly large horde. When that happens, small and manned fortifications would be able to keep the horde distracted until help arrived, given how most zombies tend to only target a single thing at a time. This can result in some great moments, if zombies appear that are significantly more tactically-minded, leading a horde straight past the bunkers to the city of DC. The military would have probably gotten quite used to the strategy, and response times would have gotten slow after 19 years of learning how the things worked. 121