Land Use Growth And Development

Published Date: 02 Nov 2017

The climate of Hillsborough River watershed can be classified as humid subtropical. Annual precipitation is about 50 inches and 60 percent of this total occurs during June through September and regularly there are convective afternoon and evening thunderstorms.  These storm events in summer can cause flooding problems in areas where there are deficiencies in existing storm water systems. However, some of the largest rain events occurred in the winter months, in late 1997 and early 1998, and this is especially true in El Nino years. Normal monthly precipitation is greatest in August(8.3 inch) and least in April(1.52 inch). (Hillsborough watershed management Plan, 2000)

The annual mean temperature in Hillsborough River watershed is about 72 degree. The mean temperature ranges from 60 degree in January to 82 degree in August and summer temperature ranges from approximately 70 degree in the morning to 90 degree in the afternoon. Humidity does not show a discrepancy as seasonally as temperature and rainfall According to the National Weather Service in Ruskin. For evapotranspiration analysis limited data are available but approximately 39 inches per year have been reported and Maximum evapotranspiration rates occur in June (Hillsborough watershed management Plan, 2000). 

2- soil,infiltration and runoff

There are useful information, such as water table depth, natural vegetation permeability and drainage classification in the SCS Manual for Hillsborough County for each soil type. Soil types can be classified in four groups regard to their runoff potential. These groups are used for infiltration rate estimation and moisture capacity. Group A soils have a high rate of water transmission and high infiltration rates and are about 10 in/hr when dry and 0.5 in/hr when saturated. Group B soils have moderate infiltration rates and a moderate rate of water transmission. Their infiltration rates are 8 in/hr when dry and 0.4in/hr when wet. Group C soils have low infiltration rates and a low rate of water transmission. Their infiltration rates are 5 in./hr  when dry and 0.25 in./hr when saturated. Group D soils have very slow infiltration rates and a very low rate of water transmission. Their infiltration rates are 3 in./hr when dry and 0. 10 in./hr when saturated. During the dry season infiltration rates increase and runoff rates decline to Group A or Group B levels. Primary soil groups in the Hillsborough River watershed include the Myakka, Basinger, Holopaw and Pomona-EauGallie. A sequence of fill and disturbed soils occur  in the urban and suburban areas of the watershed.

 Figure 1 shows average monthly rainfall and river flow over the period 1968–2 005:

                                                                            

                                                                                          Figure 1: Average monthly rainfall and river flow over the period 1968–2 005

Figure 2 shows Runoff in Florida:

                                       

                                                                                                                 Figure 2: Runoff in Florida

 There are four physiographic provinces in The Hillsborough River watershed; the Zephyrhills Gap, the Brooksville Ridge, the Gulf Coastal Lowlands, and the Polk Upland (White 1970).

The Zephyrhills Gap that is in the south of the Brooksville Ridge encompasses the greatest portion of the Hillsborough watershed and contains the entire main river channel. This province is an erosional watershed with little movement of surface drainage and karst features (SWFWMD 1996) and elevations are between 10-140 feet.

The Brooksville Ridge that extends from northern Hernando County into eastern Pasco County has the most irregular topography and the highest elevations in the watershed are in this province with elevations as high as 300 NGVD feet (SWFWMD 1996).

The Gulf Coastal Lowlands that is in the west of the Brooksville Ridge covers the area of Big Cypress Swamp. Soils types are sandy with little organic material and elevations are between 20 and 100 feet. (SWFWMD 1996).

Polk Upland Province is in the southern part of Hillsborough watershed and elevations are generally between 100 and 130 feet. (SWFWMD 1996).

                                                     

                                                                                                           Figure3  Tampa Bay/Anclote River Watershed Distribution of Soil Hydrologic Groups

3- Physical features and landforms

There are five hydrologic units in hydrologic flow systems of the watershed: 1) the surficial aquifer; 2) semi-confining beds and the intermediate aquifer; 3) theUpper Floridan aquifer; 4) the middle confining unit; and 5) the Lower Floridan aquifer.

The surficial aquifer: It consists of sandy clays of Miocene which range in thickness from 20 feet to 50 feet (Wolansky and Thompson 1987)

Semi-confining beds and the intermediate aquifer: They separate the surficial aquifer from the underlying Upper Floridan aquifer and composed of silt and sandy clay.

The Floridan aquifer: It consists of two zones, the Upper Floridan aquifer and the Lower Floridan aquifer. It comprises of the limestone and dolomite beds of Eocene to Miocene (Wolansky and Thompson 1987). In the upper and lower reaches of the Hillsborough river watershed, flow is increased by groundwater discharges from springs. Crystal Springs, located near the city of Zephyrhills, discharges an average of 60 ft3/s in the upper watershed. In addition, localized areas with increased ionic content occur in the vicinity of some portions of the watershed.

4- Land Use, Growth and Development

The Hillsborough River watershed consist of a wide variety of land uses/covers as a result of urban, industrial, suburban, commercial and agricultural development. 59 percent of the land within the watershed is considered developed. Agriculture areas cover 32 percent of the watershed, urban areas 25 percent and transportation 2 percent. In the southern quarter of the watershed urban areas dominate the landscape. Recently, by expanding population growth and land development, forested uplands remain undeveloped along portions of the Hillsborough river watershed. However, natural lands comprise 39 percent of the watershed. The upper reaches of the tributaries, land uses are primarily rangeland, pasture and agriculture. The southern portions of watersheds of the watershed are urban and industrial, while the northern and central portions are rural. Between 1980 and 1990, the population of Pasco County increased approximately 45 percent from 193,700 in 1980 to 281,100in 1990 and the population of Hillsborough County increased from 646,900 in 1980 to 834,100 in 1990, or by 29 percent.(Bureau of Economic and Business Research 1993).  Figure 4 shows  Hillsborough River Watershed Distribution of 1990 Land Use/Cover:

                                                               

                                                                                  Figure 4:  Hillsborough River Watershed Distribution of 1990 Land Use/Cover 

5- Groundwater

The interaction between surface water and groundwater within the watershed is described in several reports (Wetterhall, 1964; SWFWMD, 1988a, 1988b, 1996; Wolansky and Thompson, 1987). Some studies evaluated the level of interaction for specific areas of the watershed including the Cypress Creek area (Detection Sciences, 1986), the Sulphur Springs area (Stewart and Mills, 1984). Some reports assessed the risk of sinkhole formation in the Hillsborough River.

Some groundwater flow models have been developed (Ryder, 1978; Ryder and others, 1980; Fretwell, 1988). Ryder and others (1980) developed a model to simulate groundwater withdrawals at the Morris BridgeWellfield and Ryder found that only 10 percent of the water pumped was derived from the Hillsborough River when the river was completely connected to the surficial aquifer and he found the degree of connection between the river and aquifer. Wolansky and Thompson (1987) did analytical computations near the river and found that groundwater withdrawals have negligible to significant effects on the river's flow. Heaney and others (1986) determined pumping impacts on streamflow and water-table elevations at the Cypress Creek wellfield in central Pasco County. The southwest Florida water management district has designed water resource assessment project for Hillsborough River Watershed ((SWFWMD, 1996) to detect the impact of groundwater withdrawals and results show that the future groundwater withdrawals may have effects on streamflow, lake and wetland systems. Figure 5 shows Hillsborough River Watershed Ground Water Pollution Potential to the Floridian Aquifer

                                                           

                                                                       Figure 5:  Hillsborough River Watershed Ground Water Pollution Potential to the Floridian Aquifer

6- Surface Water Quality

The Hillsborough River is an important for residents of Tampa and provides high quality recreational opportunities for area tourists.  Providing conditions which promote the biological health of aquatic resources will ensure the maximum benefit from the resource now and in the future.Water quality problems are Nutrients, Total suspended solids, Metals, pesticides and pathogens.

High concentrations of nitrogen and phosphorus can cause blooms of algae in water. Algae blooms can reduce dissolved oxygen level and may cause taste problems in drinking water. They can create toxins which are harmful. Total suspended solids can reduce the availability of oxygen and may include sources of pollution for aquatic life.

Pesticides and heavy metals also reduce the clarity of water and their decay products may accumulate in sediments to concentrations that are harmful to aquatic life. Pathogens can cause skin rashes and they are not usually tasted for by most water sampling agencies.

Water quality of Hillsborough River has been reviewed by Florida Department of Environmental Protection. Other reports by various researchers discuss water quality in specific regions of the watershed and much of the following discussion is from the Florida Water Quality Assessment Reports (Paulic and Hand 1994; Bureau of Water Resources, FDEP, 1996).

The Environmental Protection Commission of Hillsborough County usually publishes a summary of water quality for the stations they monitor in the County and some of the Tampa Bay tributaries (HCEPC 1995).

In some reports authors rated water quality in some basins based on the Non-point Source (NPS) Assessment. River flow is increased by discharge of Crystal Springs in the vicinity of Zephyrhills, and the waters become more swift and clear but concentrations of Nitrate and Nitrogen have increased from 1mg/l in 1970 to present day concentrations of near 2.4 mg/l (SWFWMD 1994) . Big ditch, which drains the area dominated by the CFI phosphate processing, has poor water quality due to rangeland runoff but recently has been rated as fair.

Itchepackesassa Creek has poor water quality because of high concentrations of Nutrients, bacteria, and toxics. (Bureau of Water Resources, FDEP, 1996b)

New River, Hole Branch and Hollomans Branch have poor water quality due to high concentrations of bacteria, TSS, ammonia, and low dissolved oxygen. (Bureau of Water Resources, FDEP, 1996b)

From Hillsborough River State Park south to the confluence with Flint Creek, water has good conditions and has retained much of its natural vegetation.

The USEPA designed the superfund program, for the removal of hazardous wastes from numerous dumping sites in the United States and 130 hazardous waste sites were identified in the Tampa Bay Region. Within the Hillsborough River there are seven superfund sites that are contaminated by heavy metals.

A nutrient loading model was developed for the Tampa Bay Estuary Program (TBEP) (Zarbock et al., 1994) which estimates nutrient loads and TSS loads to Tampa bay and sources of nutrients and TSS in the model included point and NPS, and atmospheric deposition. Total nitrogen loading was estimated to be 39 tons per year and total phosphorous was estimated to be 98 tons per year. (Zarbock et al., 1994)

The future estimation loads in Hillsborough Bay shows a modest increase in total loading of nitrogen and TSS, and a small decrease in phosphorus loading. Figure 6 shows Hillsborough River Watershed Non-Point Source Loading Potential:

                                                               

                                                                                           Figure 6: Hillsborough River Watershed Non-Point Source Loading Potential

7- Plant and animal communities

Hillsborough River is home to many fish species, along with dolphins and manatees and the shallow waters of the river make it an ideal place for shrimps, crabs, clams and oysters. Hillsborough River’s waters are salty with salt water from the Gulf of Mexico and freshwater flowing from tributaries and rivers from inland Florida. Plants that are native to the Hillsborough River include ornamental grasses, day lilies, Mexican petunias and bamboo plants and they require less fertilization or irrigation and are adaptable to the shifts between drought and sudden rainfall that can happen in the area. In addition, these Native plants are more resistant to pests in the area. Hillsborough River has a wide range of trees; include the palmetto tree, oak, hickory, sweet gum and the well-known mangrove trees and Native trees can withstand the extreme shifts in rainfall, the bright sunlight and the many local pets and wildlife that affect growing conditions in the area.Hillsborough's forests are crucial to maintaining the water quality of River, mitigating flooding and maintaining a diversity of natural plant and animal communities. At the same time these forest lands promote the physical health and quality of life of watershed residents. Despite these multiple benefits, forests in the Hillsborough watershed continue to be at risk.

 8- Social and economic systems

Services and retail trade have dominated the economy of a four-county area of Tampa bay and approximately 52 percent of the workforce in the region was employed within Services and retail sectors. (Tampa Bay Regional Planning Council 1999)

Other employment categories based on 1999 survey included Manufacturing 7.6 %, Construction 5.25%, financial/insurance/real estate 8.4 %, Transportation/Public Utilities 4.02%  and Farm 0.97%. (Tampa Bay Regional Planning Council 1999). Table1 shows Tampa Bay Region Employment by Category (in Thousands):