**Course Title: Floodplain Management**

**Module 5:** Policy: Rivers as a legal battleground

**Session 26**: Human occupancy of floodplains and urban riverfronts

**Author:** Frank Westerlund, Ph.D.

**Time 75 minutes**

**Objectives: (PP 1 and PP 2, Title and Objectives)**

At the end of this session, students will be able to:

Objective 26.1 Discuss the history and evolution of human occupancy of
floodplains and urban riverfronts

Objective 26.2 Identify values people place on floodplains and
riverfronts

Objective 26.3 Identify planning and design principles for human use of
floodplains and riverfronts that optimize values and sustain natural
system functions

**Scope:** This session discusses the importance of riverside
developments and how their role has evolved. The values we placed on
rivers have changed and we are now in the process of rediscovering our
rivers. This session also introduces some basic design principles to
guide this renaissance.

**Readings:**

*Student and Instructor Reading:*

Brower, David. "Session 9: Hazards Mitigation Planning." *Principles and
Practices of Hazards Mitigation,* FEMA Higher Education Course.\
<http://training.fema.gov/emiweb/edu/completeCourses.asp>

Marsh, William M. 2005. "Landscape Planning." *Environmental
Applications*, 4th ed.

*Additional Instructor Reading:*

Hunt, Constance Elizabeth with Verne Huser. 1988. *Down by the River,
the Impact of Federal Water Projects on Biological Diversity.* Island
Press*.*

Lynch, Kevin, 1965. *The Image of the City.* MIT Press.

Worster, Donald. 1985. *Rivers of Empire: Water, Aridity, and the Growth
of the American West*. Oxford University Press, 1992 edition.

**General Requirements:** It is expected that the student has completed
the previous course material.

**Objective 26.1**

**Discuss the history and evolution of human occupancy of floodplains
and urban riverfronts.**

**Remarks:**

**I. Floodplains and the rise of civilization**

> A. Civilization began in floodplains and next to rivers.
>
> 1\. Floodplains provided the environmental conditions and natural
> resources for the first large scale cultivation of land and the first
> permanent agricultural communities, in the valleys of the
> Tigris-Euphrates, Nile, and Indus Rivers (\~5,000 BC).
>
> B. These civilizations developed as "hydraulic societies", to use the
> term of historian Donald Worster. (*Rivers of Empire* 1985).
>
> 1\. They were organized around the manipulation of water and
> floodplains---drainage and/or irrigation; modification of river banks;
> construction of levees, dikes, ditches, canals; leveling of fields and
> draining or filling of wetlands; and introduction of non-indigenous,
> domesticated plants and animals. **(PP 3, Ancient Cities)**
>
> C. The social and political organization required for a hydraulic
> agricultural economy led to emergence of the first cities, such as Ur
> on the Euphrates, marking the beginning of a linkage between
> agricultural and urban occupancy of floodplains that has persisted
> through history.
>
> 1\. The pattern of cities developing in floodplain agricultural
> regions as a hierarchy of market centers also serving
> political/administrative functions was replicated throughout Europe
> and later North America.

**II. Rivers and the development of interior cities in the United
States**

> A. Rivers were the primary transportation network of the country
> during its westward expansion from the late 18^th^ to the mid 19^th^
> century.
>
> 1\. Cities and towns developed on the Ohio, Mississippi, Missouri,
> Tennessee, Cumberland, Alabama, Arkansas, Red, Rio Grande, Sacramento,
> Columbia and Willamette, as well as many smaller coastal rivers.
>
> 2\. This development occurred because these cities and towns accessed
> agricultural regions within and tributary to the valleys of these
> rivers, and they provided access to river borne transportation to
> national markets.
>
> B. In America, unlike the examples from antiquity, the river towns
> were often settled first, and their existence promoted the development
> of agricultural hinterlands that in turn fostered the growth of these
> towns into cities.
>
> 1\. The Mississippi River system alone encompassed over 50 main and
> tributary rivers once navigable by steam vessels for a total distance
> variously estimated at 9,000 to 16,000 miles.
>
> 2\. During the 19^th^ century some 8,000 steamboats operated on this
> system, and steam navigation played a central role in the agricultural
> settlement and urbanization of the entire central U.S. (Hunter, Louis
> C. 1949, 1993. *Steamboats on the Western Rivers, An Economic and
> Technological History*).
>
> C. Agricultural settlement involving the clearing of Midwest forests,
> ditching of fields, draining of wetlands, and channelization of
> streams led both to more frequent severe floods and to reduced flows
> in rivers.
>
> 1\. These efforts led to a loss of navigability in much of the
> system---this despite efforts at river "improvement" through snag
> removal, dredging, bank stabilization, and introduction of slack water
> systems on smaller tributaries.
>
> D. During the age of river transportation, riverfronts were the focus
> of urban life and economic activity.
>
> 1\. Daguerreotype photographs of the Cincinnati riverfront in 1848
> (**PP 4, Cincinnati River Front**) show a two-mile stretch of public
> landing along the Ohio River lined with warehouses, stores, shipping
> and trading companies, shipyards and marine service industries,
> hotels, amusement and other businesses that constituted the city's
> original "downtown." Fifty-two steamboats are evident, of more than
> 4,000 vessel arrivals that occurred there that year.

**III. Rivers and railroads**

> A. By the late 19^th^ century, railroads had become the dominant mode
> of transportation.
>
> 1\. The pattern of urban centers established by river transport
> remained and remains today, as does continuing urbanization around
> these cities and in their floodplains.
>
> B. Railroads were the first of many influences that caused cities to
> gradually turn their backs on their rivers. This occurred in stages.
>
> 1\. Many early rail lines paralleled rivers and rail yards and depots
> were built in the level land of floodplains or along riverfronts where
> connection could be made to river transport.
>
> 2\. Over time, railroads brought about a reorganization of the
> nation's urban hierarchy and transportation network.
>
> 3\. Major rail routes became independent of rivers but tended to cross
> them at established river cities where markets could be tapped as well
> as municipal contributions to bridge construction.
>
> 4\. Second-generation rail terminals were built away from the river,
> often in relationship to second-generation downtowns that sought
> higher, less flood-prone land set back from the river.

**IV. Rivers, highways, and motor transport**

> A. The private automobile produced a new scale and pattern of urban
> expansion largely unrelated to the river, except to the extent that
> level land in floodplains was attractive from the standpoint of lower
> up-front development cost.
>
> B. Main-stem river traffic did not disappear in all cases, but evolved
> to barge transport of bulk commodities such as coal and grain that
> required only a few specialized facilities along the length of a
> river, bypassing existing urban riverfronts.
>
> C. Riverfront districts declined into marginal uses and disuse,
> property owners often unable to cope with the cost of recurrent flood
> damage.

**V. Rivers and modern cities**

> A. Construction and periodic raising of levees and floodwalls, while
> providing some protection from more frequent moderate flood events,
> also served to separate cities functionally and visually from their
> rivers.
>
> B. With the massive industrialization that occurred in most cities
> from the 1880's through the 1920's, the major functional role of
> rivers became that of sewers for transport of both industrial and
> domestic wastes, even as most river cities relied and still rely on
> their rivers for potable water supply.
>
> 1\. In Chicago Illinois before 1900, the Chicago River carried wastes
> from the city's human population, the stockyards and its burgeoning
> industry into Lake Michigan.
>
> Students should read the paragraphs included as a Session 26 reading
> "Chicago's Dubious Distinction: First City of Filth" for a mental
> picture of the problems associate with the Chicago River in the 1800s.
>
> 2\. When the river was seen as a fire hazard and began polluting the
> city's Lake Michigan supplied drinking water, the flow was reversed
> and diverted through the Sanitary and Ship Canal into the Mississippi
> drainage basin.
>
> a\. This reduced the pollutants entering Lake Michigan at the expense
> of those living down river. (**PP 5, Chicago River**)

3.  Less urbanized areas also took advantage of their rivers ability to
    transport wastes. The City of Ogden Utah is not unusual in its
    taking advantage of the City's name sake river's ability to remove
    wastes. And, like other smaller communities a domino effect occurred
    ,and unattractive uses discouraged from other more attractive
    locations such as City dumps and salvage yards, located along the
    river. (**PP 6, Ogden River**)

**VI. Rivers and urban renewal**

> A. Primary treatment of urban sewerage did not become common practice
> until the late 1950's.
>
> 1\. Secondary or higher levels of treatment to national water quality
> standards awaited the Environmental Protection Agency (EPA), the Clean
> Water Act and subsidy programs that began in the 1970's.
>
> B. The federally financed, so-called urban renewal programs of the
> 1940's through the early 1970's led to the wholesale clearing of
> riverfront districts in many cities.
>
> 1\. Urban renewal often resulted in the loss of historical, cultural
> and architectural resources and values often unappreciated at the
> time.
>
> C. The first generation of redevelopment in these areas was often
> unrelated to the river yet massive in terms of environmental and
> visual impacts.
>
> 1\. Highways, including elevated or below-grade expressways often
> integrated with levees or floodwalls were the final step in the
> structural separation of the city from its river as well as the
> imposition of hard edge and extensive impervious surface along river
> shorelines.
>
> 2\. Sports facilities with attendant parking lots or structures
> covering tens to hundreds of acres were another common feature of this
> period of riverfront redevelopment.

**VII. Riverfront evolution**

> A. Since the 1970's and especially during the past decade and a half,
> we have seen a gradual reawakening to the historic, cultural and
> amenity values of rivers in cities, and a second, in some cases a
> third generation of riverfront redevelopment to try to recapture those
> values.
>
> B. Cincinnati, Ohio provides an example of each of these phases of
> riverfront evolution.
>
> 1\. The city was among the earliest to institute citywide planning and
> zoning when it adopted a city manager form of government in 1925,
> however the first comprehensive plan ignored the riverfront district,
> terming it "unrecoverable."
>
> 2\. The 1937 flood, worst in the city's history, accelerated the
> district's decline, and a 1939 redevelopment plan called for clearance
> of all buildings and removal of streets for a distance of six blocks
> back from the river along two miles of riverfront, the entire lower
> terrace of the city.
>
> 3\. The plan envisioned a four-lane parkway and baseball park,
> retaining the public landing and leaving much of the area in parks and
> open space.
>
> 4\. By the time the clearance took place in the early 1960's, the
> parkway was expanded to an eight-lane below-grade Interstate freeway
> segment, separating downtown from the river.
>
> a\. The stadium, completed in 1970, had expanded to become a huge
> multipurpose sports facility built on top of what had been the
> historic public landing.
>
> b\. Riverfront Stadium and its parking structure incorporated an
> elaborate flood proofing system, making it one of the most expensive
> such facilities built up to that time.
>
> c\. Parking lots and an indoor coliseum completed the development,
> effectively covering the entire riverfront with concrete impervious
> surface and hard shoreline edge (**PP 7, River Front Stadium**).
>
> 5\. Almost as soon as this redevelopment was completed, there was a
> realization that important community values related to the river had
> been sacrificed.
>
> 6\. The steps that Cincinnati has since taken to reverse this
> recognized mistake and restore its riverfront are described later in
> this session as an example of urban design approaches for urban
> riverfronts.

**VIII. Urban expansion into floodplains**

> A. As their riverfronts evolved, river cities have also shared in the
> urban expansion that has typified U.S. metropolitan areas since World
> War II.
>
> B. Many river cities in the Midwest have seen substantial decline in
> central city population since the 1960's, though most metropolitan
> areas have continued to grow, in many cases at least doubling in
> population since that decade.
>
> C. Of greater consequence is the extent of urbanized land area, which
> has increased by a much larger factor, and has involved extensive
> development in floodplains and in elevated sub-basins adjacent to
> floodplains.
>
> D. By the mid-1980's, in a number of U.S. urban areas, 20% or more of
> the urbanized area was in floodplains.
>
> 1\. Examples include
>
> a\. Charleston, South Carolina with 40% of the urban area in
> floodplain
>
> b\. Fargo, North Dakota, also with 40%
>
> c\. Dallas with 22%
>
> d\. Omaha, Nebraska with 33%
>
> e\. St. Louis with 30%
>
> f\. San Jose, California with 29%
>
> g\. Monroe, Louisiana with 81% of its urban area in floodplain.
>
> 2\. In the case of large cities such as Dallas and St. Louis, the
> total extent of floodplain urban area was immense, about 140 square
> miles in each case (Griggs and Gilchrist 1983)
>
> E. Urban expansion in floodplains is not limited to the older river
> cities and their environs. Younger, high-growth metropolitan areas in
> the Sunbelt and Far West, including cities not historically connected
> to major rivers, also have had increasing problems with floodplain
> development.
>
> 1\. Examples would include development on or near dry washes, arroyos
> or alluvial fans subject to flash floods or debris flows in areas
> around several southwest cities, and urban expansion into formerly
> rural valleys in many parts of California and the Pacific Northwest.

**Objective 26.2**

**Identify values people place on floodplains and riverfronts**

**Introduction**

As the foregoing brief history illustrates, human occupancy of
floodplains and riverfronts is deeply rooted in historic patterns of
rural and urban land use, and in cultural values attached to these
environments and uses.

As is common in a complex society that has evolved over a long period,
some of these values conflict with others. On the one hand, we adhere to
a romantic vision of America as a land of rivers essentially natural in
character; rivers that embody aesthetic ideals of nature and wilderness;
rivers that provided a stage for exploration, pioneer settlement and the
advance of civilization; rivers that gave identity and sense of place to
hundreds of communities (Mancall 1996)

At the same time we have exploited the short-term economic values of
rivers as conduits for waste, as sites of cheap, easily developed
floodplain land or of investment in rapidly appreciating riverfront view
property, while tending to discount long-term or externalized costs
associated with flood hazards, erosion, pollution, and habitat
destruction. A more dispassionate view must recognize values related to
legitimate and necessary human uses of floodplains and riverfronts that
are sustainable and not destructive of those environments.

**Remarks:**

**I. Economic value and use of the water supply**

> A. A fundamental resource value of rivers and flood plains is water
> itself, for agricultural, industrial, and domestic purposes, and for
> the conveyance of water that has been used, with or without
> accompanying waste products.
>
> 1\. This water resource includes both surface water in rivers and
> streams and groundwater, the latter consisting of both the
> near-surface water table of most flood plains, and larger groundwater
> basins that have approximate but not exact correspondence to
> topographic river basins.
>
> B. The various human uses of water represent potentially competing and
> conflicting values for river resource use, as well as potential
> conflict with natural systems such as fish habitat, that in turn have
> economic use value.
>
> 1\. Value conflict arises over both the quantity and quality of
> available water, and increasingly, the relationship between the two.
>
> C. Given this competition for a limited resource, the legal and
> political issue of water rights has assumed major importance. Two,
> conceptually different water rights value systems continue to exist in
> the United States. (Refer to Session 21 of this course)
>
> 1\. East of approximately the 100^th^ Meridian, where rainfall and
> surface water is relatively abundant, the tradition of *riparian water
> rights* is generally in force, meaning that owners of land bordering
> rivers or streams are entitled to reasonable use of that surface water
> for domestic and economic uses of their property.
>
> 2\. Further west, the doctrine of *prior appropriation* applies,
> meaning that water users who are first in time have priority rights.
>
> a\. This requires a codified and managed water rights system, which is
> an established function of state government in western states.
>
> 3\. Of growing concern within these state water rights systems is the
> need to reserve publicly held water rights to ensure minimum river and
> stream flows for environmental purposes such as fish habitat.
>
> C. Rights to groundwater use are an increasingly controversial issue
> that is much less defined in law.
>
> 1\. Groundwater extraction at higher rates than natural recharge can
> drastically reduce summer stream flows and can disrupt wetlands, cause
> land subsidence, and other problems.
>
> 2\. Mining of "fossil groundwater" in deep aquifers such as the
> Ogallala Aquifer in the western Great Plains can lead to the depletion
> of a non-renewable resource, with severe economic consequences---in
> this case the collapse of an irrigation-based agricultural economy in
> many areas.
>
> 3\. Pollution of groundwater aquifers from industrial activities and
> inadequately regulated suburban and exurban development on home septic
> systems in floodplains is another area of value conflict.

**II. Water and agriculture**

> A. Human use-related values must include the fundamental, original use
> of floodplains for agricultural purposes.
>
> 1\. Floodplains provide the most important and extensive areas of
> prime agricultural soils in most parts of the U.S., the major
> exception being the glacially deposited till plains of the Midwest and
> eastern Great Plains.
>
> 2\. The single most productive agricultural region of the United
> States, the Central Valley of California, is largely a floodplain of
> the Sacramento and San Joaquin Rivers and their tributaries.
>
> a\. The Central Valley is also experiencing some of the most rapid
> rates of conversion to urban use in the country, unlike the somewhat
> comparable Willamette Valley in Oregon where conversion has been
> constrained by state-mandated growth management.
>
> B. Agricultural use, especially with conventional and prevalent
> practices, should not imply low impact on physical and biological
> systems of floodplains and rivers.
>
> 1\. When forested floodplains are converted to agriculture, rates of
> surface runoff can increase dramatically along with lowered water
> tables, soil loss, and sedimentation of streams.
>
> 2\. Drainage of wetlands and channelization of streams to drain fields
> further contributes to heightened flood hydrographs downstream.
>
> 3\. Use of fertilizers can produce excessive nutrient enrichment in
> streams. Herbicides and pesticides are sources of pollution.
>
> 4\. Irrigation, either with river water or ground water, can lead to
> reduction in stream flows through evaporative or transpiration losses
> or through the lowering of the water table.
>
> a\. Irrigation can also result in soil salinization and concentration
> of pollutants.
>
> b\. Mitigation of these many impacts is beyond the scope of this
> chapter, however a science of sustainable agriculture that addresses
> all of these issues is under active development and should be
> incorporated in any watershed-level planning that encompasses
> agricultural uses of floodplains.

**III. Commodity transport/navigation, power production, and fisheries**

> A. Use of some rivers for efficient barge transportation of bulk
> commodities was noted earlier, a major example being the transport of
> Appalachian coal to power plants in the Ohio and Mississippi Valleys.
>
> 1\. This use is the major justification for the system of low dams and
> locks that insures almost year-round navigation on the Ohio and Upper
> Mississippi rivers.
>
> 2\. A negative aspect of this is the necessity of locating power
> plants every 50 miles or so along these rivers, where they can be
> supplied with coal and can utilize the river for supply of cooling
> water.
>
> a\. The cumulative hard edge of these large plants and their
> associated ports and coal storage facilities is significant.
>
> 3\. Air pollution from these power plants in the form of sulphur and
> nitrogen oxides is transported long distances by prevailing winds,
> causing acid rain and acidification of lakes in the Northeast U.S. and
> Canada.
>
> a\. Another negative consequence is coal strip mining above the
> headwater streams of the Ohio River and resulting water pollution
> downstream.
>
> B. The lower Missouri River is used for barge shipment of grain.
>
> 1\. The lower river has been straightened, narrowed, and deepened
> through bank stabilization, cutting off connection to back channels,
> and use of groins or "wing dams" extending partway into the river.
>
> 2\. Upstream dams constructed for flood control are managed to insure
> flows adequate for continuous navigation.
>
> 3\. Barge transport has declined while demand for recreational uses of
> the river have increased, leading to pressures for revised management
> of water flows that mimic natural conditions conducive to restoration
> of riverine habitat.
>
> a\. Proposals to restore back channels and wetlands in the floodplain
> would require this modified flow regime. (**PP 8, Rivers as
> Inter-coastal Waterways)**.
>
> C. Until quite recently, major federal investment has been made in
> navigation-related modification of many rivers, some of them enormous
> in scale and involving significant impact on floodplains.
>
> 1\. An example is the Tennessee-Tombigbee Waterway project which links
> the Tennessee River and the Gulf of Mexico via 450 miles of canalized
> or straightened and dredged rivers with dam and lock systems.
>
> 2\. Designed to provide a navigation alternative to the Mississippi,
> since its completion in 1985 the Tenn-Tom Waterway has not achieved
> projected levels of use (Hunt, 1988
>
> 3\. Economic use of rivers for hydroelectric power production and
> other purposes served by large dams is another major subject beyond
> the scope of this session.
>
> a\. However, electric power, recreation, wildlife, habitat and passage
> for anadromous fish, and water supply for agricultural, industrial and
> domestic uses all represent potentially competing and conflicting
> values for river resource use and related human use of river
> shorelines and floodplains.

**IV. Values Related to Habitation and Amenities**

> A. Continued human habitation in river communities and continued
> growth of many of those communities must be assumed, especially given
> the lack of any overriding national or state policy that would divert
> settlement and growth away from rivers.
>
> B. As a result of the National Flood Insurance Program (NFIP),
> floodplains themselves have been treated somewhat differently in
> policy from more elevated riverfront or river valley environments.
>
> 1\. It is not evident that this program has negatively affected the
> growth or general attractiveness of many river communities. By
> limiting some risk, NFIP may have had the opposite effect.
>
> C. People are attracted to live in river communities today, as they
> have been historically, for economic opportunities afforded by these
> locations and, increasingly, for a range of amenities they offer.
>
> 1\. These include views, proximity to nature and wildlife, and various
> on-shore and offshore water-related activities.
>
> 2\. In addition to scenic and recreational amenities, river
> communities offer a sense of place-based cultural identity reflected
> in many facets of community life, from festivals and other public
> events that celebrate river-related heritage to the preservation and
> adaptive re-use of riverfront built form and artifacts, whether they
> be buildings, bridges, riverboats, docks, or historic sites and
> districts.
>
> D. The challenge presented to comprehensive planning for river
> communities is certainly to balance and resolve conflicts among these
> use values, but more importantly to limit or adjust human uses in
> order to minimize or mitigate their impacts, so as to sustain or
> restore the natural system functions that support these values in the
> first place.

**Instructor Note:**

The remainder of this session presents some concepts, tools, and
examples that can be described as:

-   Low Impact Development (LID) that sustains natural system functions
    and reduces risk in floodplains and higher portions of watersheds,
    and

-   Reduced impact development and urban design that reduces risk and
    reinforces amenity values in urban riverfronts.

**Objective 26.3**

**Identify planning and design principles for human use of floodplains
and riverfronts that optimize values and sustain natural system
functions**

**Remarks:**

**I. Higher elevation portions of river basins, watersheds, sub-basins**

> A. All of the following measures will contribute to limiting or
> avoiding increase in the flood hydrograph (peak discharge rate over
> time) in mainstem streams or rivers as compared to natural conditions,
> at the same time avoiding or reducing dependence on upstream dams for
> flood hazard reduction.
>
> 1\. In both the higher elevation portions of regional watersheds and
> in smaller elevated sub-basins adjacent to floodplains, it is best to
> manage land use/land cover and employ development practices that:
>
> a\. Limit the percentage of surface runoff and maximize its overland
> concentration time
>
> b\. Increase upstream detention through primarily natural systems such
> as wetlands, and maintain soil infiltration and groundwater recharge.
>
> c\. Where dams are retained, their flow regime should be managed to
> more closely mimic natural flows, including seasonal flood pulses
> (refer to Session 13 of this course).

**II. Hydrologic models**

> A. Hydrologic models that have traditionally been used for engineering
> purposes can function effectively as planning models to guide land use
> and development.
>
> 1\. Most basic of these is the so-called "rational model" for
> computing Q, the peak discharge from a watershed or sub-basin unit. Q
> is determined as a function of:
>
> a\. The area of the watershed unit.
>
> b\. The cumulative coefficient of runoff for the unit, a percentage
> based on area-proportional runoff coefficients for land cover, slope,
> and soil types.
>
> c\. The overland concentration time.
>
> d\. The maximum rainfall intensity that can occur during the
> concentration time.
>
> e\. Manning's coefficient of roughness in the discharge stream channel
> **(PP 9, Rational Method**).
>
> B. Land use variables that affect discharge rate will vary depending
> on the general type of land use, whether it is forest resources
> utilization, agriculture, or urban or suburban development.
>
> 1\. For example, forest resources land use practices related to
> hydrologic performance include such variables as harvest mode (e.g.,
> selective vs. clear cutting), harvest pattern (large vs. small clear
> cuts, spacing), length of planting/harvest cycle, regrowth treatment
> practices (e.g., thinning), management of undergrowth and fuels,
> management of harvest slash, retention vs. removal of snags and other
> woody debris, density and pattern of forest road networks, road
> construction/maintenance practices, and management of drainage within
> harvest and regrowth areas.
>
> a\. This set of forest use factors differs in most particulars from
> that involved in agricultural or urban development.
>
> b\. This chapter focuses on urban and suburban land use practices, but
> placed within the larger context of basin-wide land uses.

**III. Urban Development**

> A. In urban development, as in other cases, variables include land
> cover during and subsequent to disturbance\--in particular the extent
> of impervious and semi-pervious surfaces with high coefficients of
> runoff, their spatial distribution in relation to slopes and soil
> types, and the overland concentration time in any area as governed by
> natural or designed runoff and drainage pathways. Key principles are:
>
> 1\. Minimizing the impervious footprint of buildings, parking lots,
> and streets.
>
> 2\. Allowing for storage and ground percolation.
>
> 3\. Slowing and extending the path taken by surface runoff.
>
> B. Drainage paths can take the form of at-surface preserved or
> restored natural drainage net, or a constructed system of swales
> (shallow depressions).
>
> 1\. At-surface drainage path systems offer many opportunities to
> increase concentration time and slow velocities though circuitous
> routing, along-path detention and percolation, and channel surfaces
> with high Manning's roughness.
>
> 2\. Buried drainage in culverts or storm sewers generally have the
> opposite effect and can contribute to drastically increased flood
> hydrographs downstream.
>
> 3\. On-site detention and/or retention through preservation or
> restoration of natural wetlands, or through engineered systems
> employing wet well or dry well technologies provide another category
> of land use and design approaches to minimize the hydrologic impact of
> development.
>
> 4\. **PowerPoint slide 10** illustrates a general concept for low
> impact suburban residential development within a small sub-basin unit.
> Developable land units are delineated which occupy areas of higher
> elevation within the unit, though not necessarily at the highest
> elevations where steep slopes may pose problems. Development sited
> within these units is designed to minimize the size of footprints
> having impervious surfaces, or to employ other techniques that
> mitigate the effects of impervious surfaces (see later discussion of
> site-level design). Overland drainage flow from impervious surfaces
> and from the developable land units as a whole may be directed in part
> to on-site detention facilities, but primarily it is routed through a
> system of swales that provide a circuitous path of maximum length
> leading eventually to a central conveyance zone that becomes
> coincident with the mainstem stream channel and floodplain exiting the
> sub-basin unit. Reference: Marsh, [Landscape Planning, Environmental
> Applications]{.underline}, 3^rd^ ed, 2001. (**PP 10, LID for Suburban
> residential Development**)
>
> C. The swale system should where possible utilize natural drainage
> paths, but can include constructed swales that can serve other open
> space use functions under normal runoff conditions, e.g., greenbelts,
> walkways, bike paths, wildlife corridors.
>
> 1\. Swales can be designed with underlying soil, sand, and gravel
> layers to maximize percolation, and with surface vegetative ground
> cover that maximizes roughness and minimizes flow velocity and
> erosion.
>
> 2\. The central conveyance zone is likewise kept in open space, with
> protected forest, wetland or other naturally occurring vegetation and
> its consequent woody debris.
>
> 3\. All these elements work together to minimize overland runoff,
> increase percolation and groundwater recharge, maximize concentration
> time, minimize the flood hydrograph, and protect wetlands, riparian
> zones, and hyporheic zones.

**IV. Land use planning tools**

> A. Cluster or planned unit development zoning and subdivision
> ordinances provide some of the land use planning tools that can
> implement a low-impact development pattern of this type.
>
> 1\. Planned unit development (PUD) typically permits clustering of
> lots and buildings at higher densities on designated portions of a
> large development site in exchange for open space set-asides for
> identified functions and purposes, resulting in the same average
> density specified by underlying zoning.
>
> 2\. Subdivision regulations, whether applied to a PUD or conventional
> development, can be used to control the configuration of buildable
> lots and delineate specific tracts to remain in open space.
>
> a\. For example, open space tracts can be designated at the heads of
> natural drainage or stream channels where gradients are steepest and
> retention of natural vegetation can minimize acceleration of runoff at
> these points.
>
> 3\. Some other mechanisms include:
>
> a\. Public purchase of open space, development rights, or conservation
> easements.
>
> b\. Use of impact fees, special assessments, or surface water utility
> charges to generate revenue for purchase of land or development
> rights, for construction and management of drainage systems, for
> buy-out of floodplain properties, or funding home elevation subsidy
> programs.
>
> c\. Reduced property taxation for open space set-asides, based on
> hydrologic function and public benefit.
>
> d\. Transfer of development rights between property owners; and
>
> e\. Property owner donation of conservation easements to a land trust
> in exchange for taxation and other advantages.
>
> B. At the level of the individual building site, there are a number of
> low-impact development techniques that can be employed to make the
> site mimic natural hydrology.
>
> 1\. Runoff from rooftops can be channeled via gutters into perforated
> buried pipes that slope downward underneath "rain gardens" with plants
> that naturally thrive in areas of high soil interflow.
>
> a\. Such a system can prevent nearly all water collected by roofs from
> becoming overland surface runoff.
>
> 2\. "Conveyance furrows" filled with gravel or crushed rock can be
> used to convey water from a building into shallow gravel-filled
> trenches that allow for ground absorption, or into a swale system as
> described earlier.
>
> 3\. Driveways and sidewalks can be constructed of porous materials
> such as glued-together gravels.
>
> 4\. Streets can be paved with porous asphalt and can utilize modified
> curb or curb less street edge systems that direct remaining rainwater
> into swales.
>
> 5\. Employing all of these techniques can reduce runoff from an area
> of single family residential development by as much as 90% compared to
> conventional practices.
>
> a\. Performance zoning and/or building codes that incorporate
> performance standards related to hydrology offer tools for
> implementing these types of design approaches (**PP 11, LID site
> design)**.

**V. Land use management, downstream floodplains, and river corridors**

> A. Within floodplains, a dominant principle should be to avoid or
> strictly limit development of buildings, structures, parking lots, and
> transportation infrastructure that restricts the conveyance of
> floodwaters or raises the base flood elevation as represented for a
> 100-year flood on a FEMA Flood Insurance rate Map (FIRM).
>
> 1\. The National Flood Insurance Program (NFIP) requires participating
> communities to elevate new residential development above the base
> flood elevation and to floodproof other new development.
>
> a\. This may involve elevation of structures with open ground floors,
> but more commonly results in elevation on fills that individually and
> cumulatively raise base flood elevations.
>
> B. Elevating structures without the use of fill is certainly
> preferable and where fill is unavoidable, the use of LID practices
> should be considered.
>
> 1\. Impacts can be especially severe where large structures such as
> shopping malls or mega store structures occupy major portions of
> floodplain fringes.
>
> a\. Often the NFIP encourages the building of such structures by
> allowing Letters of Map Amendment or Revisions through the use of fill
> (LOMR -- F) (http://www.fema.gov/fhm/ot_lmreq.shtm)
>
> C. Although the NFIP addresses risk of water inundation, it is silent
> on risks associated with sediment, erosion, and waterborne debris.
>
> 1\. NFIP does not recognize or incorporate the natural beneficial
> values of the floodplain, though FEMA has published companion
> documents that encourage incorporation of practices that may enhance
> natural values.
>
> 2\. The NFIP standard accepts a one-foot rise in flood elevation
> within a conveyance area defined as a floodway, and prohibits new
> development in the floodway unless it lies in the hydrologic "shadow"
> of existing development.
>
> 3\. However, the floodway as defined is typically a small portion of
> the overall floodplain.
>
> a\. It is difficult or impossible for a community to apply a one-foot
> standard in managing urban growth cumulatively and over time across a
> floodplain, given that local ordinances under NFIP permit each new
> development to occur when elevated on fill.
>
> D. A *zero-rise standard*, as adopted by a number of communities in
> the U.S., removes the artificial distinction between a floodplain and
> a floodway, recognizing that under natural conditions the entire
> floodplain of a river is a conveyance area.
>
> 1\. A zero-rise policy is more restrictive of floodplain development,
> but need not be interpreted as a "zero-development" policy.
>
> 2\. Significant development can occur, by building on existing fills,
> building in the shadow of existing development, or by mitigating new
> development by increasing conveyance area through the setback of
> levees or by providing compensatory storage elsewhere in the
> floodplain (**PP 12 Zero Rise**)
>
> E. Another concept is *a density floodplain.*
>
> 1\. It would be based on some maximum allowable increase in water
> surface elevation, perhaps less than one foot, but this would be
> calculated based on a maximum percentage of the floodplain's area that
> could be filled.
>
> 2\. That percentage could be applied to each property---it might be
> 10% of a parcel's area that could be filled for development, or a
> sliding scale of buildable percentage based on parcel or lot size,
> with a larger percentage for small lots.
>
> 3\. Also, any open space set-asides would figure into the equation,
> allowing a larger buildable percentage for the remaining area. A
> density floodplain could thus be implemented through existing types of
> zoning mechanisms.
>
> 4\. In all cases, land use planning for floodplains should emphasize
> flood tolerant open space land uses, especially those that preserve
> natural vegetative cover such as nature preserves, wildlife refuges,
> wetland areas, and parks and recreation areas oriented to passive,
> nature-directed activities.
>
> F. Agriculture, though it has significant impacts on hydrology and
> aquatic biosystems, does represent the dominant, established land use
> in many floodplains, and conversion from agriculture to urban uses
> constitutes a major disturbance that can destabilize existing natural
> systems. **(PP 13, Buffers)**
>
> 1\. Agriculture is relatively tolerant of flood conditions compared to
> urban land use.
>
> 2\. These are practical reasons for conserving and maintaining
> existing agricultural use in floodplains where restoration to prior
> natural conditions is not feasible.
>
> 3\. Agricultural zoning has been an effective tool for accomplishing
> this in many counties. Many of the previously mentioned land use
> management tools such as purchase of development rights and
> conservation easements would apply also.
>
> G. Other concepts for land use management in floodplains include the
> following:
>
> 1\. Protection or restoration of natural storage within floodplains.
>
> 2\. Wetlands protection through "critical areas" or similar local
> ordinances is a key element.
>
> 3\. Also important are aspects of stream restoration that reconnect a
> stream to back channels, abandoned channels, oxbows, and other
> portions of its floodplain.
>
> 4\. Buffers, setback requirements where structures are required to be
> set back from the bank of a stream or river.
>
> a\. In part, this coincides with the FEMA floodway development
> prohibition; however, buffers should be designed to serve many
> purposes in addition to allowing conveyance.
>
> b\. Several of these pertain to a buffer's potential role in
> protecting native riparian vegetation that can filter pollutants from
> runoff into the stream, provide organic nutrient sources for the
> stream, and modulate stream temperature by providing shade.
>
> c\. Buffers can also protect a significant portion of a stream's
> hyporheic zone, allowing water to pass between that zone and the
> surface.
>
> d\. The width of required buffers is a controversial issue and
> ultimately may not be appropriate for standardization in codes, but
> rather should be based on performance related to the set of functions
> served in the context of localized physical and environmental
> conditions.

**VI. Near channel development**

> A. Near channel development that is outside of the floodplain can have
> an adverse impact on natural functions as well as the long-term
> survivability of the development.
>
> 1\. FEMA floodplain maps steer development to higher elevations that
> are not necessarily safer or supportive of natural physical or
> biological processes.
>
> 2\. High banks may appear ideal for building flood safe structures,
> but may contain fine-grained soils subject to rapid erosion and
> failure of cut banks.
>
> 3\. High banks may also be strategic to the riparian functions
> discussed above.
>
> a\. High bank development can reduce the complexity, diversity, and
> resiliency of the river corridor, while removing vegetation that
> deters erosional processes.
>
> b\. Buffer design should therefore incorporate protection of high bank
> areas that support riparian functions.
>
> B. Establish floodplain zones for flood frequencies less than 100
> years (e.g., 10, 25 or 50 years), with different land use controls or
> development mitigation requirements for each zone based on the
> differing levels of hazard.
>
> 1\. For example government buyout and removal of structures in the
> 1-10 year zone.
>
> 2\. Flood proofing of existing development and prohibition of new
> development in the 10-25 year zone.
>
> 3\. Regulation based on a density floodplain concept in the 25-50 and
> 50-100 year zones.
>
> C. Encourage or subsidize the elevation of building structures using
> open-story ground floors that do not obstruct floodwaters.
>
> 1\. Where a floodplain is located in a seismic hazard zone, elevated
> structure systems must provide sufficient sheer strength to resist
> seismic forces.
>
> 2\. Identify depth and velocity zones and regulate their development.
>
> D. The FEMA regulatory floodway is not always the only area where
> swift floodwaters pose a danger to life and the built environment.
> Other overflow channels can carry deep or high velocity flows.
>
> 1\. Building elevation requirements may not be sufficient to provide
> protection, and development prohibitions or special engineering
> requirements may be needed.
>
> E. Set back existing levees or dikes to increase conveyance area and
> to allow a river to re-establish more natural conditions in the
> near-channel portion of its floodplain, allowing for channel migration
> and re-connection to back channels and wetlands.
>
> 1\. Lower or redesign levees and dikes to overtop at certain
> flood-tolerant locations during peak flows of major floods, both to
> re-introduce flood pulses to adjacent land and to lower the downstream
> flood hydrograph.
>
> 2\. Coordinate levee and dike systems throughout a floodplain so that
> flood impacts are equitably distributed.
>
> F. Develop computer-based hydrologic models specific to every river
> basin and employ them as regional land use planning tools.
>
> 1\. Analysis using such models would make it possible for planning to
> be tailored to the physical characteristics and the existing and
> projected land use and development conditions of each basin.
>
> G. Expand upon such concepts as buffers, set-back levees, wetlands,
> riparian and other open space protection through the creation of
> regional "greenways" and greenway systems that preserve linear
> corridors of open space along the main stems of rivers.
>
> 1\. Such corridors can provide for a variety of recreational uses
> while allowing conveyance of floodwaters, reducing vulnerability,
> protecting natural systems, and preserving scenic as well as cultural
> and historic resources along a river.
>
> 2\. Greenways fit into both rural and urban environments, providing
> connection between the two, and they can address in a combined way our
> varied sets of values that relate to rivers.

**VII. Urban Riverfronts** - **Cincinnati and its efforts to restore an
urban riverfront and its connections to the city**

> A. The loss of values related to the city's Ohio River setting was
> realized soon after completion of the massive redevelopment of the
> 1960's.
>
> 1\. In the mid-1970's, as a Bicentennial project, over a mile of
> riverfront upstream of the redeveloped area was acquired by the city
> and developed for passive and active recreation, with walkways,
> viewpoints, interpretive signs and displays related to the natural and
> human history of the Ohio River.
>
> 2\. Although this linear park incorporated considerable green space,
> it was decided not to recreate a more natural shoreline.
>
> a\. Instead, a major structural feature, the Serpentine Wall was
> constructed, a sinuous line of steps extending along and down into the
> river **(PP 14: Cincinnati Port**).
>
> b\. While extending the "hard edge", the stepped wall does allow
> access to the river at all river stages (water levels) for fishing,
> kayaking, and other activities, that, with river cleanup, are even
> expected to include swimming.
>
> B. These efforts did not satisfy demands to redress the ill-conceived
> redevelopment of the central riverfront.
>
> 1\. In 1999 Cincinnati embarked on one of the largest re-redevelopment
> projects in U.S. history, including removal of Riverfront Stadium and
> construction of new sports facilities on either side of the central
> riverfront area, which will be devoted to parks, museums, a
> reconstructed public landing, and restoration of about a half mile of
> natural shoreline **(PP 15 and 16: Cincinnati River Front**).
>
> 2\. The new baseball park, at one end of the development, is much
> smaller in footprint than the previous stadium and incorporates
> flood-tolerant design less expensive to build.
>
> 3\. Lidding of the below-grade freeway will enable reconnection of the
> riverfront to the city, and on the lid, a mixed-use neighborhood is
> being developed with design and architecture that reflect the historic
> context of the original riverfront district (**PP 17: Cincinnati River
> Front**). See [www.cincinnatiport.org](http://www.cincinnatiport.org/)
> and [www.riverfrontplanning.org](http://www.riverfrontplanning.org/)).
>
> B. This project depended in part on impetus provided by and investment
> made in the new generation of sports facilities; however, the fact
> that a medium size city would invest hundreds of millions of
> additional dollars to re-establish its connection to a river speaks to
> the powerful values associated with rivers in our culture, especially
> as symbols of place.

**VIII. Urban design**

> A. Urban design is a branch of urban planning that deals with the
> spatial, functional, visual, and aesthetic/psychological
> interrelationships of built form, open spaces, and natural
> environment.
>
> B. Urban design offers many tools that can be applied to the problem
> of effectively integrating an urban environment with a river
> environment.
>
> 1\. Some of these tools, such as Kevin Lynch's well-known typology of
> mappable urban form features such as districts, paths, edges and
> landmarks (Lynch, [The Image of the City]{.underline}, 1965) can be
> applied directly to analysis of urban riverfronts, and perhaps can be
> further adapted for this purpose.
>
> 2\. The following are a number of urban design and development
> approaches, many of them employed in recent and current riverfront
> efforts in U.S. cities:
>
> C. Davenport and Muscatine, Iowa (**PP 18, Muscatine Iowa; PP 19,
> Davenport, IA.**).
>
> 1\. Remove or avoid building levees or floodwalls in the central
> portion of the urban riverfront to preserve the city's "window" on the
> river.
>
> D. Gateway Arch Park, St. Louis, Missouri (**PP 20, Saint Louis Water
> Front**).
>
> 1\. Where flood protection is required in the central riverfront,
> replace the floodwall or existing levee with a gradually sloping levee
> surface, with winding pedestrian pathways, overlooks, and green space
> oriented to passive recreation. In this manner, it is possible to
> employ a levee that does not look like a levee and invites access to
> the river.
>
> 2\. Alternatively, move levees or floodwalls back from the river and
> reserve the riverfront area for open space and other flood tolerant
> uses. This approach is especially suited for restoration of "soft
> edge."
>
> E. The "Moonwalk," New Orleans, Louisiana and Savannah River levee in
> Augusta, Georgia (**PP 21, Moonwalk and PP 22, Savannah levee**).
>
> 1\. Where existing levees cannot be removed, develop pedestrian access
> across and along the top of the levee with walkways, viewing
> platforms, interpretive displays.
>
> F. Cincinnati, Ohio.
>
> 1\. Put highways paralleling the river below grade, lid portions of
> them, and develop lids with uses appropriate to a riverfront district.
>
> G. Old Sacramento, Sacramento, California **(PP 22, Old Sacramento,
> California).**
>
> 1\. Move or site parallel highways back from the river, preserving
> riverfront districts.
>
> H. Tom McCall Riverfront Park, Portland, Oregon. **(PP 23, Tom McCall
> Riverfront Park)**
>
> 1\. Remove riverfront highways and replace with parks and open space.
>
> 2\. Control building heights and the orientation of buildings to
> preserve views of the river from the city.
>
> I. Laclede's Landing and the Eads Bridge, St. Louis.
>
> 1\. Restore historic riverfront districts or representative portions.
> Find adaptive uses for buildings that are economically viable.
>
> 2\. Preserve historic riverfront artifacts such as early bridges and
> docks. Provide localized structural flood protection as needed.
>
> J. Chattanooga Aquarium, Chattanooga, Tennessee. World's largest
> aquarium of freshwater environments, incorporated into the city's
> Tennessee River Greenway.
>
> 1\. Limit development to river-related uses. Clearly, this may require
> broad definition and can include everything from port activities,
> marinas and water-based recreation to uses that reflect natural,
> historic and cultural values related to the river.
>
> K. Edmonton, Alberta and Saskatoon, Saskatchewan
>
> 1\. Use riverbanks and shorelines primarily for passive recreation
> activities that do not require paved surfaces, structures, or "hard
> edge." Expand linear "soft edge" to the maximum extent possible within
> the urban area.
>
> 2\. These two Canadian cities provide remarkable examples of planning
> designed to maximize the length of soft edge shoreline of major rivers
> passing through metropolitan areas.
>
> 3\. Edmonton has established continuous green space and soft edge
> along both sides of the 50 km length of the North Saskatchewan River
> passing through its metropolitan area.
>
> 4\. Saskatoon has an even more ambitious program implemented through a
> regional "river edge authority" responsible for conservation, habitat
> restoration, recreation, historic preservation, interpretation and
> public education programs along a 60 km stretch of the South
> Saskatchewan River (**PP 24, Saskatoon**). See the website of the
> Meewasin Valley Authority: www.meewasin.com.
>
> L. Willamette River Greenway, Portland to Eugene, Oregon **(PP 25,
> Willamette River Greenway).**
>
> 1\. Connect and incorporate urban riverfronts into citywide,
> metropolitan, and regional greenway systems.

**In class exercise:**

The instructor should give the students 10 minutes to discuss how the
human uses of their case study rivers has evolved, how the stakeholders
and the stakeholder values have changed and identify the current
stakeholders and the values that are driving decisions today.

Student should also offer a couple of design tools that might be
considered by today's stakeholders that would support their values.

This discussion could be within Case Study Teams with each Team
reporting to the class as a whole or as a general class discussion.

***References**:*

Brower, David. "Session 9: Hazards Mitigation Planning." *Principles and
Practices of Hazards Mitigation,* FEMA Higher Education Course.
<http://training.fema.gov/emiweb/edu/completeCourses.asp>

Chan Krieger and Associations, Hargreaves Associates, and Development
Strategies Inc. 2005. "Downtown Riverfront Workshop." Davenport, Iowa.
[www.cincinnatiport.org](http://www.cincinnatiport.org/)

Griggs and Gilchrist. 1983. *Geologic Hazard, Resources, and
Environmental Planning.* Wadsworth Publishing Co.

Hill, Libby, 2000, *The Chicago River: A Natural and Unnatural History*,
Lake Claremont Press, pages 99 -100 and 112 -113

Hunt, Constance and Verne Huser. 1988. *Down by the River:* *The Impact
of Federal Water Projects and Policies on Biological Diversity.* Island
Press.

Hunter, Louis C. 1949, 1993. *Steamboats on the Western Rivers, An
Economic and Technological History*. Dover Publications.

Lynch, Kevin. 1960. *The Image of the City.* MIT Press.

Mancall, Peter C. ed. 1996. *Land of Rivers, America in Word and Image*.
Cornell University Press.

Marsh, William M. 2005. *Landscape Planning, Environmental
Applications*. John Wiley and Sons. (4^th^ ed).

Willamette Greenway Project
http://www.co.multnomah.or.us/dbcs/LUT/land_use/zonordin/wrg/wrg_index.html

Worster, Donald. 1985. *Rivers of Empire: Water, Aridity, and the Growth
of the American West.* Oxford University Press (reprint 1992).