Zoning, for example, is an indispensable tool for implementing planning, but too weak for some metropolitan situations and often too inflexible to meet certain needs. If essential open space has been protected only by zoning, astronomical increases in its speculative value may generate enough pressure on zoning boards to change the category, as happened last year on upper Rock Creek. This is particularly true in view of metropolitan plans' inevitably hodgepodge nature, which makes them somewhat arbitrary and vulnerable to attack. Bribery and personal-interest scandals often are rooted in zoning matters. Furthermore, residential zoning of the standard minimum-lot-size sort, not adapted to cluster housing and such sophistications, may actually encourage sprawl and rectilinear violation of the landscape by restricting the density of people in a place where the density of buildings and pavements is what really matters. [Illustration: THE HYDROLOGIC CYCLE] Tax systems can be troublesome in various ways--discouraging public purchase of needed parks or conservation areas because officials don't want the land to go off the tax rolls, preventing renewal of blighted areas by penalizing improvements, running farms out of business by taxing their fields as subdivision land, promoting leapfrogging and sprawl (in the case of Federal capital gains taxation) by rewarding speculative retention of tracts. And other government programs and policies at various levels work against good planning or have done so in the past, either by failing to encourage good types of land use or by actively promoting bad types. Traditional Federal mortgage insurance and home loan practices oriented toward standard suburban development are an example, and so are many highways and roads subsidized and routed by experts in higher realms of government. With so much economic and legal muscle arrayed on the side of chaos and a whole army of enterprising folk dedicated to its perpetuation--some holding seats on planning and zoning bodies--the wonder is that the metropolitan counties have been making any headway at all with improving their planning process. And they have been, especially since they have begun to work together in such organizations as the Metropolitan Washington Council of Government. But, as elsewhere throughout America, the progress is somewhat dwarfed by the population pressures and untrammeled expansionism planning must deal with. Radical measures may be needed; there has been sober talk of counties' issuing bonds, condemning all vacant land within a wide radius of the city, and buying it up for gradual resale and development in an orderly and sensible way, thus eliminating at one stroke the speculative pressures and torsions that are the root cause of much of the trouble.