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ee ee .. point of view. It creates a series of small detention ponds all along the flow line, imitating the natural movement of water through an undeveloped landscape. In the Woodlands new community outside Houston Texas, culverts are not put under driveways with this rural roadside drainage scheme. Every home has the equivalent of a small infiltration basin along the roadside in the front yard. Driveways are dipped slightly at the right-of-way line to create a kind of check dam/fording combination. In large (infrequent) storms, runoff overflows the driveway connecting the line of basins into a functioning swale. In small storms, runoff flows into the basins and infiltrates into the soil, recharging groundwater and restoring pre-development base flows. In areas where soils are heavy or groundwater is high, the roadside swales could still be fitted with culverts under the driveways to promote good drainage. Another positive feature of rural road sections is that it tends to encourage roads being placed high in the landscape, along ridges. This is much better from a hydrologic performance point of view as it disconnects impervious surfaces from the main channels of runoff flow. Because the roads are high, they do not become places where runoff is concentrated. Instead, runoff amounts corning off roads are small and can be carried along side lot lines to the open space areas behind homesites, or channeled in overland systems along the back lot lines. Both are places where it is easy to preserve natural drainageways. All these techniques promote post-development runoff velocities and discharges that are much closer to pre-development levels than do the 'standard' curb, gutter and storm sewer approaches so typical of suburbia. Incidentally, developments with roadside swales rather than storm sewers were standard before W orId War II. The use of roadside swales tended to result in a net reduction of storm water runoff discharges from new subdivisions compared to those produced by the pre-development agricultural cropland conditions. On the other hand, curb-and-gutter streets tend to produce higher runoff velocities and discharges than those produced by pre-development conditions. This is because the use of curb and gutter requires the use of storm sewers (which are by definition convenience systems, not flood control systems). Sewers are required to let the water out of the 'bath tub' effect created by the curbs. Since storm sewers are gravity flow systems they tend to want to be in the low areas in the landscape. These are the natural drainage ways. If you want to produce huge changes in base flows, create spikes in storm runoff pulses and promote downstream flooding, this is exactly the right thing to do. (However, many state and federal laws and regulations are aimed at eliminating these impacts.) The streets and storm sewer lines tend to be sited together in the low areas of the landscape. The natural drainageways and the new drainageways all become paved. Water can't soak into the ground. The smooth surfaces speed up runoff, causing a 'rush hour' effect in the runoff 'traffic' known as downstream flooding. We have come to recognize the ill effects of new development with curbs, gutters and storm sewers on runoff. To mitigate these problems, developers are now required to install runoff detention and treatment ponds to hold flood pulses on site. Developers are thus required to spend more money to remedy a problem which local zoning codes and subdivision requirements have spared no developer expense to create. Basically, standard development controls force developers to spend money to create runoff problems with required curbs and storm sewers (which rural-oriented homeowners don't want anyway) and then spend more money to mitigate the unnecessary problem. Developers pass the cost on to the homebuyer. Low income people find it impossible to find affordable housing. All these problems are created by unnecessary and unwanted curbs and storm sewers. It is important to remember that with rural sections, roads tend to be sited high, and lot runoff (except for the front yard) tends to go non-roadside drainageways (many side-lot- line and back-Iot-line swales). Instead of runoff being concentrated in one large swale Rationale for OSD changes 7 Sykes